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European Commission - DG EnvironmentWalloon Regional GovernmentProvince of Limburg - The NetherlandsProvince of Limburg - BelgiumWaterboard Roer & Overmaas

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B4-3040/97/730/JNB/C4

by

S. Dautrebande, J.G.B. Leenaars, J.S. Smitz & E. Vanthournout (eds.)

May 2000


Table of contents I

7$%/(�2)�&217(1765 SCENARIO DEVELOPMENT .......................................................................................................... 59

5.1 INTRODUCTION........................................................................................................................... 59

5.2 APPROACH ................................................................................................................................. 59

5.3 IDENTIFICATION OF ALL POTENTIAL MEASURES ......................................................................... 60

5.4 GROUPING OF MEASURES ........................................................................................................... 60

5.5 RANKING OF MEASURES PER ‘MODEL-BASED’ GROUP ................................................................ 61

5.6 SELECTION OF SCENARIOS TO BE USED IN THE STUDY ................................................................ 62

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6.1 INTRODUCTION........................................................................................................................... 65

6.2 OBJECTIVES................................................................................................................................ 65

6.3 METHODOLOGY AND APPROACH ................................................................................................ 65

6.4 INPUT DATA FOR THE HYDROLOGICAL STUDY ............................................................................ 66

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6.5 HYDROLOGICAL CHARACTERISATION OF THE GEUL RIVER CATCHMENT AREA .......................... 69

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6.6 MODEL DEVELOPMENT............................................................................................................... 72

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6.6.1.1 Soil sub-model EPIC-GRID.............................................................................................................73

6.6.1.2 The groundwater sub-model ............................................................................................................73

6.6.1.3 The master code ...............................................................................................................................73

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6.6.2.1 Preparation of the spatial data ..........................................................................................................74

6.6.2.2 Determination of initial parameters..................................................................................................76

6.7 MODEL VALIDATION .................................................................................................................. 76

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6.8 MODEL APPLICATION AND SCENARIO SIMULATION .................................................................... 80

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Table of contents II

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6.9 CONCLUSIONS ............................................................................................................................ 85

6.10 RECOMMENDATIONS .................................................................................................................. 86

6.11 ACKNOWLEDGEMENT................................................................................................................. 86

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7.1 INTRODUCTION........................................................................................................................... 87

7.2 OBJECTIVES............................................................................................................................... . 88

7.3 APPROACH ................................................................................................................................. 88

7.4 MODELLING OF THE GEUL AND ITS TRIBUTARIES ....................................................................... 89

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7.4.2.1 Topological discretisation ................................................................................................................90

7.4.2.2 Hydraulic structures .........................................................................................................................90

7.4.2.3 External boundary conditions ..........................................................................................................93

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7.5 SIMULATIONS ............................................................................................................................. 94

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7.6 CONCLUSIONS AND RECOMMENDATIONS ................................................................................. 101

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8.1 INTRODUCTION......................................................................................................................... 105

8.2 THE NETHERLANDS.................................................................................................................. 106

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8.2.3.1 National level.................................................................................................................................109

8.2.3.2 Provincial level ..............................................................................................................................110

8.2.3.3 Local level......................................................................................................................................111

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8.3 BELGIUM .................................................................................................................................. 113

8.4 THE FLEMISH REGION .............................................................................................................. 114

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8.4.1.1 Regional level ................................................................................................................................114



Table of contents III

8.4.1.3 Local level......................................................................................................................................115


8.4.2.1 Water-resources management ........................................................................................................116

8.4.2.2 Land use planning..........................................................................................................................119

8.4.2.3 Land use and agricultural policy ....................................................................................................121

8.4.2.4 Environmental policy.....................................................................................................................122


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8.5 THE WALLOON REGION............................................................................................................ 132

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8.5.1.1 Regional level ................................................................................................................................132


8.5.1.3 Local level......................................................................................................................................133


8.5.2.1 Water-resources management ........................................................................................................134

8.5.2.2 Land use planning..........................................................................................................................137

8.5.2.3 Agricultural policy .........................................................................................................................139

8.5.2.4 Environmental Policy.....................................................................................................................140


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8.6 CONCLUSIONS AND RECOMMENDATIONS ................................................................................. 150

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9.1 CONCLUSIONS ON THE TERRITORIAL DATA INVENTORY ........................................................... 154

9.2 CONCLUSIONS ON THE PRELIMINARY RISK ANALYSIS............................................................... 155

9.3 CONCLUSIONS ON THE PRELIMINARY HYDROLOGICAL ANALYSIS (CF. ANNEXE D) .................. 155

9.4 CONCLUSIONS ON THE SCENARIO DEVELOPMENT..................................................................... 156

9.5 CONCLUSIONS ON THE HYDROLOGICAL STUDY ........................................................................ 156

9.6 CONCLUSIONS ON THE HYDRODYNAMIC STUDY ....................................................................... 157

9.7 CONCLUSIONS ON THE LEGAL FRAMEWORK ............................................................................. 158

9.8 FINAL CONCLUSIONS ................................................................................................................ 159

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Scenario development 59

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This project is aimed at the identification of environment-friendly measures to decreasethe risk of flash floods in the catchment of the Geul river. Based on the assumption thatthe change in land use during the last 30-50 years is one of the factors that mayincrease the flash flood problems, two basic scenarios, representing the land use in the1950’s and the present land use, have been selected. These two scenarios can beconsidered as being representative of the changes in land use and the related increaseof fast runoff. It was obvious to all stakeholders that the current land use situation cannotbe reverted to the old 1950’s state. Therefore other measures to obtain flash floodreducing results have been identified as well. In the present chapter the procedure forselecting these measures and identifying the scenarios (or set of measures), which willbe used in the simulations, is described. The scenarios include both ‘hydrological’measures (actions in the catchment) and ‘hydraulic’ measures (actions in the riverbed).

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To develop the scenarios, a step-by-step procedure was followed:

1. Identification of all potential measures

2. Definition of coherent groups of measures

3. Ranking of measures (per group)

4. Preparation of possible scenarios (by technical team)

5. Ranking of possible scenarios

6. Selection of scenarios to be simulated in the project

The project stakeholders were requested to participate in each process-step, for this is aprerequisite for obtaining realistic and feasible scenarios and for ensuring a stronginvolvement of the regional authorities.

Due to some determinant aspects in this Geul project regarding (1) the attempt tosimulate spatially distributed aspects, for instance land use changes and agriculturalpractices, in a deterministic way, (2) the lack of knowledge concerning the hydrologicalprocess related to different land use types, (3) the requirement that the impact ofimplemented measures could be studied, and (4) the limited financial resources, severaldecisions had to be made:

1. Only three extra scenarios, at the utmost, were to be identified;

2. The scenarios should not consist of more than one measure with spatialcharacteristics (hydrological model) and one hydraulic infrastructure measure



(hydrodynamic model) in order to facilitate the analysis of the relation betweenimpact and specific measure;

3. A measure should be identified within the technical limits of the simulation models,the scale used for the model-input and the knowledge available in literature.

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Based on a review of the present literature and a brainstorming with the project-team apreliminary list of measures was formulated. The list consisted of forty-two differentmeasures, which could be divided in three major groups. These main groups ofmeasures are presented in Table 5.1; the full list is shown in Annexe F.1.

Table 5.1 Main groups of potential measures

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1. Awareness-raising measures 1.A. Based on sensitisation

1.B. Based on incentives

2. Technical measures 2.A. Related to environmental planning1

2.B. Related to infrastructure

3. Institutional measures

Of these measures, only the technical measures were relevant to be simulated in thispilot study and selected for the remaining scenario-development procedure steps.Awareness-raising measures and institutional measures have been dealt with during theanalysis of the legal framework.

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The technical measures (main group 2) were subdivided into two subgroups, namely agroup related to environmental planning (2.A) and one related to infrastructure measures(2.B). After a first selection three subgroups were maintained in group 2.A, and fivesubgroups in group 2.B. These subgroups are presented in table 5.2.

1 Environmental or land use planning



Table 5.2 Types of measures to be used in the scenario development, maintained after afirst selection process

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2.A. Related to environmental planning 2.A.1 Adjustment of the riverbed

2.A.2 Adapted land use

2.A.5 Adjustment of parcel borders - land plots

2.B. Related to infrastructure measures 2.B.2 Adjustment of the riverbed

2.A.1.b Restoration of meandering

2.B.3-4 Storage basins

2.A.2.e Buffer-zones along the river and grassed waterways

2.B.8 Bridges and structures restricting the water-flow

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In each subgroup several measures were defined. This resulted in six measures for type2.A.1, seven measures for type 2.A.2 and one measure for each of the other types (seeAnnexe F.1). Consequently, a list of approximately twenty potential measures wasobtained for the next step in the scenario-development procedure.

Up to here the scenario-development was based on the available knowledge andopinions of the participating stakeholders. The next step had to link the definedmeasures with the technical features of the simulation-programmes. Therefore arearrangement of all twenty measures was needed, based on the hydrological andhydrodynamic model characteristics. Four so-called ‘model-based’ groups weredistinguished: two groups of measures that could be implemented in a hydrologicalprogramme and two groups that could be implemented in a hydrodynamic model. These‘model-based’ groups are defined as:

1. +\GURORJ\� ,: Spatial measures related to a certain land use type, for which themeasures involve the land use practices (mainly agricultural practices);

2. +\GURORJ\�,,: Spatial measures resulting in a land use class conversion;

3. +\GURG\QDPLFV�,: Measures related to adjustments of the riverbed cross-section;

4. +\GURG\QDPLFV�,,: Measures related to the hydraulic infrastructure.

All of the twenty measures could be introduced in one or another part of the simulationmodel; some could be put in more than one of the model-based groups. Resulting were



groups with four to six measures. As the condition was made before that a scenariocould only consist of one hydrological and one hydrodynamic measure at the most (forsimulation facilitating), a ranking of measures was required.

This ranking was done by means of a scoring — or priority — procedure. In each group,every stakeholder had to select the two, according to him, most promising andappropriate measures. Based on this selection the measures were ranked, resulting inthe following list of ‘most preferred measures’ (Table 5.3, 1 = first choice, 2 = secondchoice).

Table 5.3 List of most preferred measures

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The explanation of these measures, while also referring to the codes used in Table 5.2,is given below:

- ��$��F (re)allocation/enlargement/extension of floodplains

- ��$��G creation of wetlands

- ��$��E turn high sloping areas to grassland or wood

- ��$��H re-introduction of hedgerows and green belts

- ��%�� adjustment of the riverbed (modification of cross-section geometry andhydraulic slope)

- ��%�� storage basins upstream

- ��%�� retention basins in the riverbed

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Based on the results of the ranking and the technical features of the models, thetechnical team of the Geul project defined several scenarios. These scenarios werepresented and discussed during the project-team meeting of June 1999. It finallyresulted in the selection of three future scenarios, which are combined with the reference



‘baseline-scenarios’ as defined for the historic land use in the 1950’s and the presentland use in the 1990’s.

Table 5.4 Scenarios to be simulated in the hydrological and hydrodynamic studies

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1. 1990-reference current land use actual situation

2. grass on slopes of >12% increased roughness of the river floodplains

3. forest on slopes of >10% actual situation

4. greenbelts / hedgerows addition of 2 constriction devices in the riverbed

5.1950-reference land use of the 50s actual situation

These five scenarios were simulated as part of the hydrological and hydraulic modellingstudies, described in Chapters 6 and 7 of this report.


Hydrological study 65

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This hydrological study aims at defining the characteristics of flash flood events in theGeul river catchment and, in particular, at assessing the effectiveness of land userelated measures to reduce the risk of flooding. In Annexe F.1, all possible measures arelisted. In Chapter 5, some measures are combined into scenarios. The hydrologicalmodel will simulate these scenarios.

The simulated water-inflow has three components, namely surface runoff, hypodermicflow and groundwater flow. They are simulated by means of an integrated hydrologicalmodel. Whether rainfall infiltrates in the upper layers of the soil or runs off superficially isa function of topsoil characteristics, of the soil vertical humidity profile and also of landuse characteristics (land use, crop growth, agricultural practices). Consequently, soilcharacteristics as well as land use changes will affect the infiltration of water into the soiland the superficial runoff.

The hydrological study calculates the amount and speed of water flowing from the Geulcatchment into the Geul River and its tributaries. The results of the hydrological studyare used as input for the hydraulic study (Chapter 7).

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The objective of the hydrological study is to simulate the hydrological behaviour of theGeul river catchment and to determine the water-flow to the Geul river and its tributaries.This objective is achieved by using a hydrological model of the basin.

The hydrological model generates water-fluxes as input for the hydrodynamic model ofthe river network used in Chapter 7, separately for each environmental scenario definedin Chapter 5.

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The hydrological programme used in this study is part of an integrated hydrologicalbasin-river model, named MOHICAN (02dèle +ydrologique ,ntégré pour le calcul des&rues et l'$mplitude des 1iveaux d'eau). It has been developed for the Walloon Ministryof Equipment and Transport in a multidisciplinary approach. The participatingresearchers were member of:

• three scientific departments of the University of Liège: the "Centre d'Etude et deModélisation de l'Environnement" (CEME-ULG), the "Laboratoire de Géologie del'Ingénieur et d'Hydrogéologie" (LGIH-ULG) and the "Laboratoired'Hydrodynamique Appliquée" (HYD-ULG) (the latter not being involved in thepresent study);



• one scientific department of the Agricultural Faculty of Gembloux (Unit"+\GUDXOLTXH�$JULFROH", HA-FSAGx).

The soil compartment is represented by the sub-model EPIC-GRID, describing the soil-water dynamics, particularly in relation to crop growth. The Unit "+\GUDXOLTXH�$JULFROH"(FSAGx) developed this sub-model.

The model includes soil and groundwater processes and transfers from soils andgroundwater to the river network. It uses, as much as possible, deterministic andphysically-based representations and is oriented towards planning, i.e. the simulation ofthe effect of environmental management operations or measures in the uplands of thecatchment area. The input data, which are necessary to run the programme, include:

1. Information about the SK\VLFDO�FKDUDFWHULVWLFV of the catchment area:

- physiography of the catchment area (digital elevation model, river network)

- soil characteristics

- geological characteristics

- climatic characteristics

2. Information about the ODQG�XVH in the catchment area:

- land cover types

- land use management, agricultural practices

The soil sub-model calculates direct fluxes to the river network and water-fluxes to thegroundwater (effective infiltration). The groundwater sub-system is represented bymeans of transfer functions.

The hydrological programme MOHICAN calculates the distribution of water-fluxes fromthe soil (runoff, hypodermic fluxes) and from the groundwater (base flow) to the rivernetwork, in order to feed the river flow.

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6.4.1 Limnimetric data

The limnimetric data consist of the water levels observed at nine measuring stations inthe catchment area. Each station is representative for the water-outflow of the upstreamcatchment and can therefore be used to characterise that specific part of the Geul rivercatchment. Figure 6.1 illustrates the locations of the measuring stations and thecorresponding Geul sub-catchment areas.



Table 6.1 summarises the hourly flow data and indicates whether data are missing. Thereader will remark that the data are incomplete for many years. Figure 6.2 shows typicalannual flows, measured in different limnigraphic stations.

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WatershedinHommerich149.83 km²+

WatershedinCottessen121.70 km²

WatershedinGulpen46.07km²

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WatershedinEys28.51km²

WatershedinPartij29.31km²

WatershedinSlenaken27.08km²

Limnigraphs

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Figure 6.1 Sub-catchment areas in the Geul catchment area and associated limnimetricstations, measuring the water flows.



The data quality has been assessed as well. As the simulation model requires completetime-series, the missing data were — in some cases — substituted on the basis of astatistical analysis. The results of the data analysis are presented in detail in Annexe D.

Table 6.1 Hourly discharges: available and missing data

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COTTESSEN 84% 0,2% 0,4% 30% 9% 3% 10% 0,7%HOMMERICH 25% 11% 5% 1% 3% 0,3% 2% 2% 1%MEERSSEN 16% 5% 5% X 6% 8% 14% 2% 0,3%SLENAKEN 9% X 0,4% 8% X 79% 3% 4% 63%GULPEN 7% 1% 0,8% X 0,4% 11% 5%EYS 53% 0,1% X X X X X 2%PARTIJ 60% 2% 2% 0,1% 6% 5% 0,6% 10%

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Figure 6.2 Examples of measured water flow (hourly discharge)

6.4.2 Climatic data

The climatic data, which are required as input in the hydrological model, include dailyrainfall, hourly rainfall (pluviographs), daily minimum and maximum temperatures anddaily hours of sunshine. The Thiessen Method is used for calculating the averagedprecipitation



6.4.3 Geographic data

CSO and HA-FSAGx have assembled GIS map layers of different types of data. TheseGIS layers were used as input for the simulations, and include:

- elevation (Digital Elevation Model or DEM);

- land cover (current and historic);

- river-network (Geul, Gulp, Eijserbeek, Hohnbach and Selzerbeek);

- type of soils.

The base maps were moreover used to derive secondary data (also required as input forthe hydrological simulations). More details on the available data are given in Annexe D.

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The hydrological characterisation of the catchment area includes the assessment of themeasured data and the analysis of rainfall-distribution in relation to flow characteristicvalues, measured for the current (reference) situation. The degree of correspondencebetween the amount of water supply (rainfall) and the amount of water at the outlet isanalysed in the section ‘Water balance’. The temporal variability of water flow isanalysed in the section ‘Frequency analysis (of peak discharges)’ and is illustrative forthe separation of rainfall water into surface water runoff and groundwater base flow. Thelatter will be explained in the section on hydrogeology (Annexe D, paragraph 1.5.5).

The limited number of meteorological stations, the above-mentioned lack of data forsome stations and the rather poor quality of the data hamper a statistical analysis of thereference hydrology. Nevertheless, a preliminary analysis has been performed of whichthe procedure and results are shown in Annexe D. A summary of the characterisation isgiven below.

6.5.1 Flood frequency analysis

A frequency analysis, based on the Gumbel distribution for maximum discharge values,has been performed for the maximum hourly values measured in the limnimetric stationsof Cottessen, Hommerich and Meerssen. The resulting peak discharge values for thedifferent stations are very similar. There is little difference between Meerssen andHommerich, despite the fact that the catchment area at Meerssen is two times largerthan the catchment area at Hommerich.

6.5.2 Characteristic events

An analysis has been performed for a selection of peak discharges. The averageprecipitation in the catchment is calculated at each different limnimetric station. Fast



runoff is separated from base flow and the water volumes are calculated in order todetermine the runoff characteristics. The results are summarised in Table 6.3

Table 6.3 Calculated flood hydrographs (without base flow)

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Two remarkable points can be observed:

1. Despite the catchment area being approximately two times larger at Meerssenthan at Cottessen or Hommerich, the peak flows and the flood volumes (surfacewater runoff related parts) appear not to be proportional to the catchment surfacearea at Meerssen or Cottessen / Hommerich for each specific rainfall event. Forperiods with data available at all measuring stations (e.g. December 1994), arelative correspondence can be found between the observed flows of the Geul



and the observed flows of the tributaries, giving reasonable water balances. Thusflow data are somehow questionable, but not in totality.

2. The calculated runoff coefficients at Cottessen reach up to 25 or 30% for majorrainfall events, which is a low value, but quite normal for the Geul basin. Thecalculated runoff coefficients at Meerssen are lower than 15% for major rainfallevents, which is DEQRUPDOO\ low. This could perhaps be due to the poor quality ofthe data.

6.5.3 Waterbalance of the catchment area

The annual average rainfall for the period 1993-1998 and the measured runoff issummarised for each sub-basin in Table 6.4.

Table 6.4 Measured (“Meas.") or simulated (“Sim.") mean annual balances (1993-1998)

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Cottessen (122 km²) 947 (375) (1) 316 (47,5) (39) 33

Hommerich (150 km²) 938 319 311 47,5 34 33

Gulpen (46 km²)

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949 255 357 11,2 27 38

Eys (29 km²) 864 132 299 3,8 15 35

Slenaken (27 km²)

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1037 296 393 8,0 28 38

Partij (29 km²) 897 171 315 4,9 19 35

Meerssen (341km²) 902 275 305 93,8 30 34

HA-FUSAG Gembloux (1) missing data are numerous (see Table 6.1)

For all the tributaries of the Geul river, but not for the Geul itself, one can observe low tovery low annual runoff coefficients.



The water balance in these catchments seems to indicate water losses. The poor qualityof limnimetric data at the measuring stations of Partij and Eys, makes it impossible toconclude on this topic for the Eyserbeek and Selzerbeek. However, it appears that waterlosses do occur in the Gulp catchment, for which limnimetric data are satisfying. Thesewater losses can be caused by groundwater flows.

The altitude of the Gulp river is higher than the altitude of the Meuse river (see Figure6.3), inducing a gradient from the Gulp to the Meuse. In permeable rocks, like theCenozoic and Mesozoic formations present in the basin, this gradient may be the originof groundwater flows from the Gulp basin to the alluvial plain of the Meuse river (Fig.6.3).

Figure 6.3 Groundwater circulations from the Gulp river basin to the Meuse river basin

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6.6.1 Description of the model

The integrated hydrological model MOHICAN - in the version used for this present study- simulates the water profile in the soil, the fluxes of water from soil to groundwater andthe transfer from soil water and groundwater to the river network. The model iscomposed of a soil sub-model, a groundwater sub-model and a master code, which



controls the running of the sub-models, ensures synchronisation and calculates thetransfers of water-fluxes.

6.6.1.1 Soil sub-model EPIC-GRID

The catchment area is subdivided into medium-sized grid cells (1kmx1km). Each grid-cell is divided in several non geo-referenced units, regarding land cover, crop types,slope gradient and soil type, as provided by the database in the format of GIS maplayers.

The main processes simulated by the soil sub-model EPIC-GRID are:

- infiltration;

- evapo-transpiration;

- snow accumulation / melting;

- overland flow;

- rapid and slow hypodermic flow ;

- percolation to the groundwater;

- variation of soil humidity.

The principal results (water-fluxes) are:

- overland flow (hourly);

- rapid hypodermic flow (hourly);

- slow hypodermic flow (daily);

- percolation flow (daily).

6.6.1.2 The groundwater sub-model

The soil sub-programme EPIC calculates the water flow, percolating from the soil intothe saturated groundwater zone. Its temporal transfer function and the geographicaldischarge zones are determined by the groundwater sub-programme, using respectivelydeconvolution operations and hydrogeological data (see Annexe D).

6.6.1.3 The master code

The water flow from both the soil and the groundwater compartments to the rivernetwork is calculated by the following procedure:

1. The ‘inter-cell’ transfer time (from a given grid-cell to another grid-cell) iscomputed for the overland and hypodermic flows. It is calculated as a function of



the soil surface water storage capacity, which is function of the soil surfaceroughness and of the slope.

2. The transfer time from the cell to the river network is calculated as a function ofthe distance cell-river, and depends also on the slope and the roughness of thesoil.

6.6.2 Schematisation of the catchment

The schematisation of the catchment for the hydrological modelling consists of twophases:

- the preparation of the maps that will be used as input data;

- the introduction in the programme of all parameters corresponding to the differentclasses distinguished in the input-maps.

(For more details and maps: see Annexe D.7)

6.6.2.1 Preparation of the spatial data

The sub-catchments were defined based on the DTM and the demands for thehydrodynamic simulation. They are demarcated in Figure 6.1. The hydrological modelcalculates an outflow hydrogramme at the downstream end of each sub-catchment. Thecharacteristics of the sub-catchments were derived from the following GIS map layers:

- Digital Terrain Model (Map 4.2);

- Slope map (Map 4.3);

- Current land use map (Map 4.4);

- Soil maps:

- texture

- depth

- percentage coarse fragments

- hydrological soil groups (see Figure 6.4 - Infiltration capacity of the soilsdecreasing from A to C, risk of runoff increasing - SCS method from the US SoilConservation Service - details are given in Annexe D.)



Figure 6.4 Hydrological soil groups (infiltration capacity decreasing from A to C, risk ofrunoff increasing), derived from the SCS (Soil Conservation Service of the US) soil map.



6.6.2.2 Determination of initial parameters

The soil sub-programme (EPIC-GRID) needs a number of parameter values in order tocalculate the different water fluxes for the different types of land use and soils. Most ofthese values have been obtained from reference tables: EPIC bibliography and regionalinformation concerning agricultural practices and crops parameters (for instance LAI andothers), SCS tables and Brakensiek tables. Among the most important parameters arethe so-called ‘CN parameters’ (SCS method), which are a function of the vertical soilhumidity profile (daily calculated in the model). In Annexe D, some maps are presented,showing the CN runoff parameters and thus providing an indication on the spatialrepartition of the risk of runoff (the SCS risk of runoff, which is a function of land use, soiltype, slope and soil humidity characteristics).

The groundwater sub-programme requires transmissivity values to calculate thegroundwater flow. These values depend on the characteristics of the geological layers.In Annexe D, values are given for the different geological formations of the Geulhydrogeological basin.

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6.7.1 Selection of the simulation period

Most of the available rainfall and flow data cover the period 1989-1998. This 10-yearsperiod was therefore chosen for validating and running the hydrological model. However,from this period, 4 years (1989-1992) are needed for the initialisation of the groundwaterand soil modules.

Consequently, the HIIHFWLYH simulation period covers the period January 1993 toDecember 1998 (6 years). This period includes the recent major flood events in the Geulbasin (notably January 1993, September 1993 and September 1998).

The hydrological model requires no calibration. The model is validated on the five majorflood events that occurred during the period 1993-1998:

- January 1993 (day 10 to 15);

- September 1993 (day 267 to 270);

- December 1994 (day 360 to 365);

- September 1996 (day 240 to 245);

- September 1998 (day 254 to 260).

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Figure 6.5. Simulated and observed water discharges at three measuring stations --DQXDU\��

6.7.2 Results of the validation

The effective hydrological simulation is performed on the period 1991-1993 (hourly timestep for the calculation of the runoff component).

The results of the hydrological modelling (calculated water production to the rivernetwork at three limnimetric stations) are presented for typical flood events:

- flood event of January 1993 (days 10 to 15): Figure 6.5.

- flood event of December 1994 (days 360 to 365): Figure 6.6.

- flood event of September 1998 (days 254 to 260): Figure 6.7.



Figure 6.6. Simulated and observed water discharges at three measuring stations -'HFHPEHU��

A detailed analysis of the results of the hydrological modelling shows:

- a good agreement between the observed and the simulated values of the flowregime for the upstream part of the Geul catchment (upstream Cottessen) and for thedownstream part of the Geul (Meerssen);

- a significant lowering of the peak of the flood and a lag in phase (about 12 hours) ofthe flood at Meerssen;

- a good agreement between the observed and the simulated water balances of theGeul river flow at Meerssen (335 km2), the outlet of the basin (see Figure 6.8, resultsobtained for a representative and reliable year, 1993); moderate good results areobtained at Cottessen (122 km2) and Hommerich (150 km2);

- differences in the water balances (observed and simulated) for the Gulp river (seeFigure 6.8), probably due to groundwater losses from the Gulp river/basin to thealluvial plain of the Meuse river (see § 6.5.3 and Figure 6.3); the same differences inthe water balances (observed and simulated) for the Eijserbeek and the Selzerbeek



(see Figure 6.8), but these differences are not significantly established, owing to thepoor quality of the available flow measurement data.

Figure 6.7. Simulated and observed water discharges at three measuring stations -6HSWHPEHU��

6.7.3 Conclusions of the validation

The conclusions based on the validation results are the following:

- the hydrological model is able to simulate and reproduce the hydrological behaviourof the watershed, including groundwater transfers;

- up to now, the hydrological model has not included any modelling of water lossesfrom the Gulp catchment (groundwater fluxes from the Gulp river to the alluvial plainof the Meuse river); additional data must be collected to state this process moreprecisely;



- the differences between the observed and simulated peak values of the Geul riverflow during flood events have to be interpreted as the effect of water surface flowprocesses (described by the hydraulic model, see Chapter 7).

Figure 6.8 Observed and simulated water balances for eight measuring stations

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6.8.1 Scenarios

The following land use scenarios, which were developed in Chapter 5, are used in thehydrological simulations:

1. Current land use (Map 4.4 in Chapter 4);

2. Transformation of cultivated farming land with slope higher than 12% intopastureland (see Figure D.8.3 in Annexe D);

3. Transformation of farming - and pastureland with slope higher than 10% intoforest (see Figure D.8.4 in Annexe D);

4. Transformation of all farming land into farming land with green belts (see FigureD.8.5 in Annexe D);

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1.57

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1.00

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Meerssen Cottessen Hommerich Molentak Slenaken Gulpen Partij Eys

Yearly Mean Flow - Simulations (m³/sec)

Yearly Mean Flow - Observations (m³/s)



5. Land use map of 1950’s (see Figure D.8.2 in Annexe D).

As explained in Chapter 5, only part of the management measures proposed in thescenarios can be simulated with a hydrological model (land use related measures).

Land use changes appear in each of the five chosen scenarios. Therefore, for eachscenario, specific maps have to be prepared. This leads up to five different modellingoperations and five sets of simulation results.

Table 6.5 presents the land use distribution according to the various scenarios. It mustbe noted that all scenarios are derived from the current land use map.

Table 6.5 Land use distribution according to the various scenarios

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km² % km² % km² % km² % km² %Weeded crops 32.97 9.7 17.33 5.1 31.03 9.1 29.42 8.6 �� 4.8Non weeded crops 26.43 7.8 53.66 15.7 24.07 7.1 22.77 6.7 �� 3.9Water 0.16 0.0 0.41 0.1 0.16 0.0 0.16 0.0 0.16 0.0Deciduous forest 43.48 12.8 0.0 43.48 12.8 43.48 12.8 43.48 12.8Resinous forest 6.62 1.9 0.0 6.62 1.9 6.62 1.9 6.62 1.9Buildings in agricultural area 3.26 1.0 8.24 2.4 3.26 1.0 3.26 1.0 3.26 1.0Buildings in rural area 1.22 0.4 0.0 1.22 0.4 1.22 0.4 1.22 0.4Urban area 14.77 4.3 0.66 0.2 14.77 4.3 14.77 4.3 14.77 4.3Grassland 187.07 54.9 159.89 46.9 �� 56.3 156.09 45.8 �� 64.5Orchard 5.73 1.7 52.31 15.3 5.73 1.7 5.73 1.7 5.73 1.7Main roads / railroads 8.89 2.6 0.0 8.89 2.6 8.89 2.6 8.89 2.6Weeded / non weeded crops (mixed) 6.51 1.9 5.01 1.5 6.02 1.8 5.63 1.7 �� 1.0Deciduous / resinous forest (mixed) 3.88 1.1 43.44 12.7 3.88 1.1 �� 12.6 3.88 1.1

7RWDO ��

Faculté Universitaire des Sciences Agronomiques de Gembloux

Unité d'Hydraulique Agricole

Prof. Mme S. Dautrebande

Ir. D. Deglin

Sept. 1999

/DQGXVH�RI�WKH�*HXO�ULYHU�FDWFKPHQW�DW�0HHUVVHQ�DFFRUGLQJ�WR�WKH�VFHQDULRV

(Agriculture with slope > 12%= Grassland)

(Agriculture and grasslandwith slope > 10% = Forest)

(Greenbelts)

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In scenario 2 only the steeper slopes, above 12% and currently used for agriculture, aretransformed into grassland. This measure affects only 4.8 km2 in the total catchment, ofwhich 1.9 km2 of weeded crops, 2.4 km2 of non-weeded crops and 0.5 km2 of mixedcrops. The total area involved covers about 1.4% of the total catchment area.

In scenario 3 all slopes steeper than 10%, currently cultivated or in pasture, areafforested. This afforestation covers an area of 39,1 km2, of which 3,5 km2 is currentlyused for weeded crops, 3,6 km2 for non-weeded crops, 31 km2 as grassland and 1 km2

for mixed crops. The total area is vast and represents 11.5% of the total catchment area.

Scenario 4 assumes that the planting out of green belts2 in parcels of (cultivated)farmland will influence 50% of the agricultural area. This has a major impact on thecultivated acreage and increases the grassland area with 33 km2 or 9.6% of the totalcatchment area. 2 Green belts are grass strips of several meters width along a contour line, interrupting the parcel length.



For the current land use and the 1950 land use scenario, the land use maps have beenbased on maps and satellite imagery.

6.8.2 Results

As mentioned in paragraph 6.6.3.1, the hydrological simulations are done for thecomplete period 01/01/1991-31/12/1998 (calculation of the runoff component at hourlytime steps). From this period, only the years 1993 and 1998, which are the more reliable,are used as results and analysed. The analysis is based on the comparison of themaximum discharges at the limnimetric stations.

Figure 6.9 shows the calculated results of the total water production to the river networkof the river basin at Meerssen (outlet of the Geul basin) for each simulated scenario,corresponding to the flood event of -DQXDU\� ��, and the comparison with the"reference" scenario (current situation). The observed discharge at Meerssen during thisflood event is also plotted on this figure.



Figure 6.9 Results of the simulation of all scenarios, compared to the current scenario -Total water production to the river network of the river basin at Meerssen -)ORRG�HYHQW�RI�-DQXDU\��

Figure 6.10 presents the calculated results of the total water production to the rivernetwork of the river basin at Meerssen (outlet of the Geul basin) for each simulatedscenario, corresponding to the flood event of 6HSWHPEHU�� and the comparison withthe "reference" scenario (current situation). The observed discharge at Meerssen duringthis flood event is also plotted on the figure.

Figure 6.10 Results of the simulation of all scenarios, compared to the current scenario -Total water production to the river network of the river basin at Meerssen -)ORRG�HYHQW�RI�6HSWHPEHU��

The results of the different scenarios show little difference on the total water productionfluxes. As these results reflect the implementation of the hydrological (environmental-friendly) measures only, a relative comparison may be made. In general it can be stated



that scenario 3 (transformation of farming - and pastureland with slope higher than 10%into forest) and land-oriented measures of scenario 4 (transformation of all farming landinto farming land with green belts) show the highest improvements by giving a maximumdaily water flux reduction. In the case of high rainfall events, such as the rainfall event ofSeptember 1998, scenario 3 shows a reduction of about 7% of the maximum hourlywater flux to the river network; and the land-oriented measures of scenario 4 show areduction of about 9% of the maximum hourly water flux to the river network.

In the Geul river catchment, scenario 3 (transformation of farming - and pastureland withslope higher than 10% into forest) and the land-oriented measures of scenario 4(transformation of all farming land into farming land with green belts) show more or lessthe same results as the simulation of the 1950’s.

The expected effects of these measures however remain small, owing to the relativelysmall surface area involved in the modifications (cf. Fig. 1.2 about the effect ofincreasing urbanisation) and the low runoff coefficients observed under the currentsituation (cf. hydrological analysis).

As regards the long-term ZDWHU�EDODQFH, the results of the simulation of all scenarios,compared to the "reference" scenario (current situation), are shown in Figure 6.11 (longterm averaged water production at each limnimetric station - m3/s - over the total period1993-1998). The observed values of the water discharge at these stations, if available,are also plotted on this figure.

These results show a small effect of the proposed measures on the long-term waterbalance (small reduction of the mean water discharge, less than 6%).



Figure 6.11 Long-term water balance of all scenarios compared to the "reference"scenario. Mean water flow (m3/s), period 1993-1998.

The final output of the hydrological model MOHICAN is the water flux, at each time step,flowing to each river segment. This lateral water inflow (m³/sec) feeding the river streamis calculated along the river profile for some hundreds of locations (nodes), which areobtained by discretisation of the river network. Within this set of discretised points, aboutthirty nodes are selected, where the hydrological model has to deliver water-fluxes to thehydraulic ISIS model.

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The hydrological study presented in this chapter aimed at the quantification of the waterinflow into the Geul river system under various situations and scenarios. The output ofthe hydrological modelling is also to be used as input to the hydrodynamic study (seeChapter 7).

The water inflow is simulated as a function of the soil and environmental variablescharacterising the uplands of the Geul catchment area. They include climate,topography, soil and subsoil characteristics, hydrogeology and land use.

The model proves to be capable simulating the hydrological behaviour of the Geul basinunder the current situation. As the hydrological model is using physically-based

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Simulation GE1: Current land coverSimulation GE2: Agriculture areas with slope > 12% --> Pasture/GrasslandSimulation GE3: Agriculture and Pasture areas with slope > 10% --> ForestsSimulation GE4: Agriculture areas --> Agriculture areas with greenbeltsSimulation GE5: Land cover of 1950Observations (mean 1993-1998)



representations and has not been calibrated (specifically) for the Geul basin, it has beenconcluded that the model is able to simulate the runoff and the base flow for differentland use classes and able to estimate the effects of changes in land use or agriculturalpractices. Uncertainties, however, remain in the hydrological simulation results,associated with probable losses of groundwater from tributaries of the Geul to thealluvial plain of the Meuse river.

Three main scenarios with different land use types are studied, reflecting the effects ofpossibly applicable environmental measures to reduce the (flash) flood events. Thesescenarios consider respectively all steep slopes covered with grassland, all steep slopescovered with forest and all agricultural fields protected by green belts or hedgerows.Besides these three scenarios, two reference situations are studied as well, namely thecurrent and the historic situation, characterised by the current and historic (1950’s) landuse.

The simulated water inflow, derived from runoff, shows important peaks in time, relatedto high rainfall events. From the results of the various simulated scenarios, it can beconcluded that the proposed environment-friendly measures could reduce, but onlyweakly, the peak water fluxes under high rainfall events.

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Despite the fact that their effects remain rather small (less than 10% of the hourly peakwater fluxes to the river network under high rainfall events), land-related measures suchas transformation of farming- and pastureland with slope higher than 10% into forest ortransformation of farming land into farming land with green belts, appear to contribute tothe reduction of peaks of water fluxes in the Geul catchment. It is thus recommended totake into account these environmental-friendly orientations. Moreover, a complementaryeffect on the peak discharge can be obtained with measures to be taken in the river itself(see Chapter 7).

Considering the results obtained during the present hydrological study, it is alsorecommended:

- to increase the availability and reliability of the data (rainfall, river discharge,characterisation of urban areas);

- to investigate by additional measurements and specific hydrogeological studies thequestion of possible direct losses of groundwater from the Geul catchment to thealluvial plain of the Meuse;

It is also recommended to specifically address, in a future study, the problem of soilerosion in the Geul river catchment (and not only in relation to (large) flood events).



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The ULg and FSAGx acknowledge the Ministry of Equipment and Transport (MET) ofthe Walloon Region for giving the authorisation to utilise the MOHICAN model (partimhydrology) in the scope of the present study.


Hydrodynamic study 88

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This chapter describes a hydrodynamic study of the Geul river system. The resultsreflect the dynamics of the water flow through the Geul river and its tributaries. Thedynamical flow is simulated on the basis of the results generated in the hydrologicalstudy of Chapter 6. These results include the volume and speed of water flowing into theGeul river and its four tributaries, generated for about thirty locations, also called “ISISnodes”, along the Geul river system. The water inflow rates were simulated by thehydrological MOHICAN programme (ULg and FSAGx) as a function of the hourlyvariability of weather, of topsoil and subsoil characteristics and of the land use scenariosdefined. The ISIS Flow model is used in the present chapter to simulate the waterheights and water volumes per second running through the Geul river and its tributaries.The results per scenario are presented as a hydrograph. They are illustrating theamounts of river water passing through a certain location throughout time, making peaksin river water discharge easily detectable. Results are also presented as maximum waterheights along the longitudinal profile of the Geul river system, indicating whether andwhere the water height exceeds the height of the bordering river banks andconsequently, whether and where flooding may be expected. The longitudinal profile isattached in Annexe G. The scenarios defined in Chapter 5 include two scenarios withmeasures for water retention devices in the upstream river channel.

Section 7.2 presents the specific objectives of the hydrodynamic study and Section 7.3presents the study approach. Technum and its subcontractor IMDC used the modellingpackage ISIS Flow to model the Geul river system. This modelling is briefly described inSection 7.4, including a brief description of the modelling package ISIS Flow, the modelset-up of the Geul river and its tributaries, and the calibration and verification of themodelled Geul river system. The reader is referred to Annexe E for a more detaileddescription of these sections. Section 7.5 describes the simulations; paragraph 7.5.1provides some details about the scenarios defined and paragraph 7.5.2 describes theresults of the simulations performed for the 5 scenarios. The conclusions are presentedin Section 7.6.

The scenarios defined in Chapter 5 include both environmental (land use) measures andhydrodynamic measures. The latter include:

1. the introduction of constriction devices that create additional storage on locationswhere it is allowed;

2. the increase in the roughness of the floodplain, for instance, by the introduction ofdense bushes.

It was concluded in Chapter 6 that land use changes did not lead up to significantdifferences in simulated water inflow rates (less than 10% on hourly peak values).



Hydrodynamic simulation led to similarly insignificant effects of water inflow rates onriver water discharges and river water heights, but led to significant effects of theinstallation of hydraulic devices in the upstream river canal.

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The hydrodynamic study identified the following objectives:

• Simulation of the water flow through the Geul river system

• Analysis of the impact of the different scenarios on peak discharges and water levels

• Identification of the flood-prone areas

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The researchers of Technum and IMDC followed a well-structured procedure throughoutthe modelling study to assure maximum quality of the results, namely realisticsimulations of water movement, of water discharge levels and of water levels. Thesimulations were performed in accordance with the five steps defined below:

• Data collection

The input for the model consisted of two different types of data: the topology and theboundary conditions. The topology defines the objects in the river model and wherethese objects are located relative to each other. The objects defined in this study includebridges, sluices, river cross-sections and other infrastructure. The boundary conditionsare set by the amounts of water inflow into the river, as was measured and simulated (inChapter 6) at several locations along the Geul river (hydrogrammes and hydrographs).

• Set-up of the model schematisation

The input of the topological data into the modelling package created a schematisedrepresentation of the Geul river system, or, a model. The model is like a geographicalmap, representing the location, widths and depths of the Geul river and its tributaries aswell as the location of all types of infrastructure devices in the river channel.

• Calibration

The ISIS model of the Geul river system was calibrated in order to generate realisticsimulation results. The calibration included the simulation of water flow for a well-definedsituation with available measurements of water discharge, followed by a comparison ofthe simulated and measured water discharges. The value of coefficients was adjusted tillthe simulations fitted the measurements. The calibration took place with data from



several measuring stations for high water periods. The calibration and model outcomewere verified with input of another high water period.

• Simulation

The Geul river water flow was simulated for each scenario, after the above-describedpreparatory steps were made. Time periods were selected and the associated weatherdata were the input to simulate the river water discharges and -heights for severallocations along the Geul river. This was done for each scenario and the results wereplotted on a longitudinal profile of the Geul river.

• Analysis

The simulation results were analysed and the differences among the scenarios werecompared for some selected locations along the river. The comparisons were described.

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The reader is referred to Annexe E for a more detailed description of the technicalmodelling aspects.

7.4.1 The ISIS modelling package

The ISIS Flow programme computes flow depths and discharges using a method basedon the equations for shallow water waves in open channels, the “de Saint Venantequations”. Internal boundary conditions in the ISIS Flow package include a wide rangeof hydraulic structures. The hydraulic structures and units used in the hydrodynamicmodelling of the Geul river system include the following:

- River

- Interpolate

- Conduit

- Culverts

- Junctions

- Bridges

- Weirs and spills

- Orifices

- Sluices

- QTBDY

- QHBDY



These hydraulic structures are described in Annexe E.

7.4.2 Model set-up

This section describes the set-up of the hydrodynamic model for the Geul river.

7.4.2.1 Topological discretisation

The model is built for the Geul river and its main tributaries, namely the Gulp, theEijserbeek and the Selzerbeek as well as for two smaller tributaries, the Kleine Geul andthe Geulke and two ’natural weirs’. Additionally, three canals supplying water to millswere included in the model. Note that only the Dutch tributaries were considered, due toa lack of data on river cross-sections in the Belgian part. The Geul river itself wasmodelled from the junction with the Hohnbach down to the measuring station atMeerssen. Table 7.1 lists the river branches included in the model with their total length.A schematic overview of the hydrodynamic model is given in Figure 7.1. In Annexe E,the reader will find a more detailed representation (Figures I, II, III, IV).

Table 7.1 River branches included in the hydrodynamic model.

Branch Modelled length

Geul (Belgian part) 10.780 m

Geul (Dutch part) 33.895 m

Gulp (Dutch part) 8.960 m

Selzerbeek (Dutch part) 12.000 m

Eijserbeek (Dutch part) 9.430 m

Geulke 2.500 m

Kleine Geul 1.600 m

Geulhemermolen 561 m

Oude Molen and Franse Molen 656 m

Onderste Molen 372 m

7.4.2.2 Hydraulic structures

Hydraulic structures in and along the river branches, like bridges and sluices, mayimportantly affect the water flow. Both fixed and adjustable hydraulic structures weremodelled. Fixed structures were all modelled as ’weir-units’. Table 7.2 gives an overviewof the most important modelled structures (considered as fixed).

Sluice units were used whenever the structure was regulating flow conditions. Table 7.3lists these regulating structures. The table also mentions on what basis these structuresare regulated.



Figure 7.1 Schematic overview of the set-up of the model for the Geul river system



Table 7.2 Structures modelled as fixed weirs.

Number Branch Description

1 Onderste Molen Inlet sluice, Onderste Molen

2 Oude Molen and Franse Molen Mill sluice and outlet sluice Franse Molen

3 Geul Weir at Volmolen

4 Geul Weir at Epermolen

5 Geul Embankment between Geul and watersupply canal of Wijlre

6 Kleine Geul Gated sluice

7 Geulke Oliemolen

8 Geulke IJzermolen

9 Geulhemermolen Outlet sluice of Geulhemer mill

10 Oude Molen Mill sluice Oude Molen

11 Geul Weir at Bovenste Molen

12 Geul Fish ladder at Onderste Molen

13 Geul Weir at Onderste Molen

14 Geul Side spill at Schaloensmolen

15 Geul Weir at Kruitmolen

16 Geul Concrete sill near Geulke

17 Geul Bottom drop at Meerssen

18 Geulke Stop block weir

19 - ’natural weir’ between Geulke and KleineGeul

Table 7.3: Regulating structures modelled as gated sluices.

Number Branch Description Controlled by:

1. Onderste Molen Outlet sluice Upstream water level

2. Oude Molen/ Franse Molen Outlet sluice Discharge at Cottessen

3. Geul Weir at Epermolen Discharge at Cottessen

4. Geul Walramstuw Upstream water level

5. Geul Weir at Groote Molen Upstream water level



7.4.2.3 External boundary conditions

To run a hydrodynamic model, two types of boundary conditions are required, i.e.upstream and downstream boundary conditions. The downstream boundary condition isthe rating curve of the measuring station in Meersen (QHBDY unit). The results of thehydrological modelling are the upstream boundary conditions (QTBDY unit). Thehydrological results are distributed over the hydrodynamic model in 28 different modelpoints (see schematic representations, Figures I to IV, in Annexe E). Thus the land usedependent water inflow, simulated in Chapter 6, was determinant for the hydrodynamicsimulation of the amounts and timing of water flowing through the Geul river.

7.4.3 Calibration and verification of the model

In the numerical model of the Geul river system, as it is described up to now, twouncertainties still exist: general head losses and specific head losses. Head lossessignify the difference in height (m) between the water level of a downstream location andthe water level of an upstream location at a given moment. General head losses refer tothe ‘natural’ gradient of the river itself, and are a function of the roughness coefficient ofthe riverbed and the floodplains. The specific head losses refer to the artificial gradient inhydraulic structures like sluices and are a function of the discharge coefficient at weirs,sluices etc.

These uncertainties or unknowns can be partly eliminated by calibrating (and verifying)the model results to measured values. For this calibration and verification themeasurements of the following stations can be used:

• Partij

• Gulpen

• Slenakerbrug

• Eijs

• Cottessen

• Hommerich

The measurements of the station at Meerssen cannot be used for calibration/verification,because they are used as the downstream boundary condition.

Normally a hydrodynamic model is calibrated by comparing the calculated andmeasured water levels. Because uncertainties exist on the hydrological input data(discharges), it was preferred to compare calculated and measured rating curves(communicated by the Waterboard Roer & Overmaas). Rating curves were calibrated onthe basis of rainfall data as input data, and water discharge measurements ascomparative data. Calibration was done on the period of September 24 to October 19,1993. Verification was done on the high water period of September 7 to November 29,1998.



Figure 7.2 shows an example of the fitting between calibrated and ‘measured’ ratingcurves (measuring station at Hommerich). (see also Annexe E.1)

Figure 7.2 Calculated and 'measured' rating curves for the measuring station atHommerich. Calibrated values 1993.

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7.5.1 Description

Once the hydrodynamic model had been set up, calibrated and verified, it can be used tosimulate the impact of different flood reducing measures in the river and river catchment.

Five different scenarios were modelled (see Chapter 5). The current situation, which hasbeen used for the calibration and verification, will be used as a reference. This situationis called scenario 1. An overview of the different scenarios is given in Table 7.4.

Table 7.4 Overview of the scenarios, developed in Chapter 5

Scenario Hydrological part Hydrodynamic part1. Present land use Actual situation2. Grass on slopes >12% Increased roughness of the flood plains3. Forest on slopes >10% Actual situation4. Greenbelts Addition of 2 constriction devices5. Land use of the 50’s Actual situation

92.4

92.6

92.8

93.0

93.2

93.4

93.6

93.8

94.0

94.2

94.4

0 5 10 15 20 25 30 35 404��P��V�

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These scenarios differ because the hydrological part (land use changes) and/or thehydrodynamic part of the river and its catchment have been changed. Changes in thehydrological part are described in Chapter 6. These changes can be accounted for in thehydrodynamic model by changing the external boundary conditions (see § 7.4.4). Inaddition two hydrodynamic changes have been considered:

1. Increased roughness of the flood plains: the Manning roughness coefficient of theflood plains is increased from 0.050 to 0.090 sm-1/3. The first value corresponds tothe actual situation, i.e. grass and scattered brush, whereas the last valuecorresponds to the roughness of medium to dense brush. A higher Manningroughness coefficient reflects slower water flow. This hydraulic proposition is part ofscenario 2, together with the environmental measure to introduce grassland on allslopes steeper than 12%.

2. Construction of two constriction devices: at labels GEUL16650 and GEUL26650 (forthe location of these labels: see the table of the longitudinal profile in Annexe G) twoconstriction devices are added. The location of these structures has been chosen insuch a way that upstream of these structures a large amount of water can be storedwithout severe nuisance for humans and environment. The constriction devices aremodelled here using ORIFICE units, but also other types of constriction devices(pipes, weirs…) are possible. The dimensions of these ORIFICE units have beenchosen so that the largest peaks are diminished without creating a backwater effectof more than 2 meters. The dimensions are BxH=3x2 m2 and 4x2 m2 for labelsGEUL16650 and GEUL26650 respectively. This hydraulic proposition is part ofscenario 4, together with the environmental measure to re-introduce greenbelts orhedgerows.

The five management scenarios have been simulated for three continuous periods.These periods have been chosen in such a way that they contain the most importantflooding events.

1. 93a: from 11/01/1993 20h00, to 14/01/1993 23h002. 93b: from 25/09/1993 10h00, to 28/09/1993 20h003. 98: from 13/09/1998 00h00, to 22/09/1998 09h00

7.5.2 Results

The simulation results of these five scenarios are presented in three different ways:

1. Tabular overview of the simulated maximum discharges (volumes per second) andwater levels (m) for the five scenarios in selected locations along the Geul river forthe periods 93a (Table 7.5), 93b (Table 7.6) and 98 (Table 7.7). For a description ofthe different labels used in these tables, the reader is referred to Table 7.8. Thechange in water discharge and water level, relative to the present situation(reference scenario 1), is given between parentheses.



2. Hydrographs for the five scenarios near the outlet of the hydrodynamic Geul rivermodel (Geul at Meerssen) for the periods 93a, 93b and 98 (Figures 7.3, 7.4 and 7.5),indicating the timing of water discharge.

3. Maximum water levels of the five scenarios plotted in a longitudinal profile of theGeul for the period 93b. The longitudinal profile is attached to the report as a largesized paper map (Annexe G).

When analysing these results, the following conclusions can be made:

• When looking at the maximum water levels in the longitudinal profile (Annexe G)and comparing them to the bank levels, one can see that the major floodingproblems occur upstream of the mills: Volmolen, Epermolen, Bovenste Molen,Wijlre, Oude Molen, Franse Molen and Groote Molen. Other problem areas arethe Geul river in Wallonia, near the Dutch border, and the Geul river at the mouthwith Eijserbeek and Gulp.

• When comparing the maximum discharges and maximum water levels simulatedfor the current and historical situation (scenarios 1 and 5 respectively) in Tables7.5 to 7.7, one can see that flooding problems have increased significantly duringthe last 40 years due to changes in land use. For the high rainfall events of 1993the maximum water levels in the Geul have increased by 5 to 15 cm. Thedischarges have increased by 2 to 15%. These differences between the presentland use and the land use of the 1950’s are more pronounced for the high rainfallevents of 1993 than for the high rainfall event of 1998, because in the formerones the upstream catchments are contributing relatively more to the totaldischarge.

• The situation can be improved by changing the land use again. When thesteepest slopes are covered with grass (scenario 2) only small improvementscan be noticed, even if the roughness of the flood plains is increased. When thesteepest slopes are covered with forest (scenario 3) or when greenbelts are used(land-related measures of scenario 4), the situation improves and reaches moreor less the situation of the 1950’s.

• A significant improvement in the downstream part of the Geul can be achieved byimplementing scenario 4. It includes the re-introduction of green belts orhedgerows, combined with the construction of constriction devices (like orifices,pipes…) in the upstream part of the Geul river canal, given the fact that enoughspace is available to temporary store a large volume of water. Indeed it can beseen in Figures 7.3 to 7.5 that the large peak flows downstream of theseconstructions are attenuated and delayed. Upstream of these constructionsmaximum water levels rise over a length of approximately 2 and 1 km. Themaximum rise amounts to 2.4 meter (see Table 7.6 at label GEUL16550). Bycomparing Figure 7.3 with the Figures 7.4 and 7.5, one can see that theconstriction devices as they have been implemented into the model now, havealmost no influence on the peak discharges lower than 30 m3/s.



Table 7.5 Maximum discharges and water levels at some points in the studied catchment for the5 scenarios for the first peak of the period 93a, 11/01/1993 20h00 to 14/01/1993 23h00. Betweenbrackets the difference with the reference situation�

/DEHO VFHQ�� VFHQ�� VFHQ�� VFHQ�� VFHQ��

P275 4.93 4.91 (-0.02) 4.70 (-0.23) 4.66 (-0.27) 4.87 (-0.06)

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GEUL02800 5.85 5.77 (-0.08) 5.57 (-0.28) 5.51 (-0.34) 5.80 (-0.05)

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GEUL03550 6.39 6.32 (-0.07) 6.11 (-0.28) 6.09 (-0.29) 6.37 (-0.01)

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GEUL12150 19.63 19.49 (-0.14) 18.73 (-0.90) 18.33 (-1.30) 17.57 (-2.06)

��

GEUL16550 20.47 20.32 (-0.15) 19.45 (-1.03) 19.07 (-1.41) 18.26 (-2.21)

��

GEUL26450 24.35 24.17 (-0.18) 22.97 (-1.38) 22.51 (-1.84) 21.55 (-2.80)

��

GEUL31250 20.59 20.62 (0.03) 19.81 (-0.78) 19.24 (-1.35) 18.81 (-1.78)

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GEUL33605 26.29 26.15 (-0.14) 24.88 (-1.41) 24.19 (-2.11) 23.42 (-2.88)

��

GULP09350 1.85 1.84 (-0.01) 1.85 (0.00) 1.79 (-0.06) 1.81 (-0.04)

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SELZ11200 3.05 3.03 (-0.02) 2.93 (-0.12) 2.92 (-0.13) 2.46 (-0.59)

��

EJJS08400 3.08 3.07 (-0.01) 3.01 (-0.07) 2.91 (-0.17) 2.34 (-0.74)

��

GRB00005 4.80 4.78 (-0.03) 4.49 (-0.31) 4.35 (-0.46) 4.16 (-0.65)

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GRC00005 0.82 0.82 (0.00) 0.72 (-0.10) 0.69 (-0.14) 0.62 (-0.20)

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GRD00005 0.00 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) 0.00 (0.00)

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HEMER10 8.12 8.04 (-0.08) 7.56 (-0.56) 7.37 (-0.75) 7.00 (-1.12)

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ONMO3B 0.00 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) 0.00 (0.00)

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OMFM7 5.14 5.12 (-0.02) 5.13 (-0.01) 5.10 (-0.03) 5.11 (-0.03)

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Table 7.6 Maximum discharges and water levels at some points in the studied catchment for the5 scenarios for the period 93b, 25/09/1993 10h00 to 28/09/1993 20h00. Betweenbrackets the difference with the reference situation


P275 12.33 12.29 (-0.04) 11.74 (-0.58) 11.53 (-0.80) 11.79 (-0.54)

��

GEUL02800 15.00 14.91 (-0.09) 14.28 (-0.72) 14.11 (-0.89) 14.39 (-0.61)

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GEUL03550 16.19 16.10 (-0.09) 15.34 (-0.85) 15.25 (-0.94) 15.50 (-0.69)

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GEUL12150 41.72 41.37 (-0.35) 39.03 (-2.69) 38.50 (-3.22) 38.75 (-2.97)

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GEUL16550 43.36 42.96 (-0.41) 40.50 (-2.87) 35.71 (-7.65) 40.19 (-3.17)

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GEUL26450 48.13 47.69 (-0.44) 45.01 (-3.12) 38.37 (-9.76) 44.63 (-3.50)

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GEUL31250 33.22 32.92 (-0.30) 31.77 (-1.45) 28.76 (-4.45) 31.47 (-1.75)

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GEUL33605 50.89 49.90 (-1.00) 47.28 (-3.62) 39.95 (-10.95) 46.71 (-4.19)

��

GULP09350 6.28 6.22 (-0.06) 5.77 (-0.52) 6.03 (-0.25) 5.93 (-0.35)

��

SELZ11200 5.55 5.44 (-0.11) 5.26 (-0.29) 5.07 (-0.49) 4.34 (-1.22)

��

EJJS08400 8.81 8.79 (-0.02) 8.61 (-0.19) 7.75 (-1.06) 6.48 (-2.33)

��

GRB00005 10.23 10.16 (-0.08) 9.52 (-0.71) 7.81 (-2.42) 9.40 (-0.83)

��

GRC00005 7.19 7.02 (-0.17) 6.18 (-1.01) 3.38 (-3.81) 6.00 (-1.19)

��

GRD00005 2.66 2.61 (-0.05) 2.19 (-0.47) 1.10 (-1.56) 2.11 (-0.55)

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HEMER10 19.17 18.89 (-0.27) 17.23 (-1.94) 13.47 (-5.70) 17.01 (-2.16)

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ONMO3B 0.06 0.06 (0.00) 0.02 (-0.04) 0.02 (-0.04) 0.03 (-0.03)

��

OMFM7 15.60 15.33 (-0.28) 13.50 (-2.11) 9.40 (-6.21) 13.24 (-2.37)

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Table 7.7 Maximum discharges and water levels at some points in the studied catchment for the5 scenarios for the period 98, 13/09/1998 0h00 to 22/09/1998 9h00. Between bracketsthe difference with the reference situation.


P275 16.20 16.11 (-0.09) 13.45 (-2.75) 15.21 (-1.00) 15.20 (-1.01)

��

GEUL02800 18.73 18.58 (-0.15) 15.83 (-2.90) 17.59 (-1.14) 17.55 (-1.18)

��

GEUL03550 20.26 20.12 (-0.15) 17.24 (-3.03) 19.09 (-1.17) 18.97 (-1.29)

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GEUL12150 40.03 39.68 (-0.35) 35.77 (-4.26) 36.78 (-3.25) 38.24 (-1.79)

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GEUL16550 41.18 40.73 (-0.44) 36.81 (-4.37) 34.79 (-6.38) 39.26 (-1.92)

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GEUL26450 41.77 41.33 (-0.43) 37.47 (-4.30) 34.96 (-6.80) 39.83 (-1.94)

��

GEUL31250 30.01 29.77 (-0.23) 27.98 (-2.02) 26.33 (-3.68) 29.16 (-0.85)

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GEUL33605 42.55 42.10 (-0.44) 38.40 (-4.14) 35.40 (-7.15) 40.75 (-1.80)

��

GULP09350 6.42 6.34 (-0.08) 5.86 (-0.57) 6.11 (-0.32) 5.96 (-0.47)

��

SELZ11200 3.40 3.36 (-0.04) 3.20 (-0.20) 3.11 (-0.29) 2.65 (-0.75)

��

EJJS08400 3.72 3.70 (-0.02) 3.62 (-0.10) 3.03 (-0.69) 2.96 (-0.76)

��

GRB00005 8.48 8.40 (-0.08) 7.51 (-0.96) 6.88 (-1.60) 8.06 (-0.42)

��

GRC00005 4.12 3.99 (-0.14) 2.94 (-1.18) 2.20 (-1.92) 3.60 (-0.52)

��

GRD00005 1.51 1.46 (-0.05) 0.92 (-0.59) 0.55 (-0.96) 1.25 (-0.26)

��

HEMER10 15.45 15.20 (-0.25) 13.02 (-2.42) 11.70 (-3.74) 14.36 (-1.08)

��

ONMO3B 0.36 0.35 (-0.01) 0.14 (-0.22) 0.26 (-0.10) 0.26 (-0.10)

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OMFM7 11.21 10.89 (-0.32) 8.22 (-2.99) 6.79 (-4.42) 9.75 (-1.47)

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Table 7.8 Description of the different labels

/DEHO 'HVFULSWLRQ

P275 Geul

Wallonia

GEUL02800 Geul

upstream Volmolen

GEUL03550 Geul

upstream Epermolen

GEUL12150 Geul

downstream confluence with Gulp, Ejjserbeek and Selzerbeek

GEUL16550 Geul

At first constriction device

GEUL26450 Geul,

At second constriction device

GEUL31250 Geul

upstream Groote Molen

GEUL33605 Geul

near Meerssen

GULP09350 Gulp

1 km upstream mouth

SELZ11200 Selzerbeek

1 km upstream mouth

EJJS08400 Ejjserbeek

1 km upstream mouth

GRB00005 Geulke

upstream end

GRC00005 Kleine Geul

upstream end

GRD00005 Groene overlaat

between Geulke and Kleine Geul

HEMER10 Geulhemer

mill water canal

ONMO3B Onderste Molen

mill water canal

OMFM7 Oude Molen - Franse Molen

mill water canal



• Even with the use of greenbelts and constriction devices flooding problems occurlocally (like for instance upstream of the mills). The overall behaviour of the riversystem has however improved. Local problems caused by local restrictions in thewatercourse (for instance at mills and bridges) should, however, be solvedlocally.

0

5

10

15

20

25

30

260 270 280 290 300 310 320 330 340

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GLVFKDUJH��P��V�

scenario 1

scenario 2

scenario 3

scenario 4

scenario 5

Figure 7.3 Hydrograph in Geul river near Meerssen for five scenarios, for the period 93a

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This chapter showed how a one-dimensional hydrodynamic software package like ISISFlow can be used to evaluate the influence of several flood reducing measures, in thecatchment itself as well as changes in the water body, on the discharges and waterlevels, and consequently on the flooding depths, for different locations in thewatercourse.

As an example five different scenarios were evaluated. These scenarios contained ahydrological part and a hydrodynamic part. The hydrological part of the scenarios, whichmainly focussed on the aspects of land use, was taken into account by changing theinflow of water fluxes in the ISIS model according to the hydrological calculations



(Chapter 6). The hydrodynamic part was modelled by changing the hydrodynamic modelset-up.

0

10

20

30

40

50

60

6410 6420 6430 6440 6450 6460 6470 6480 6490 6500 6510

WLPH��KRXUV�


scenario 1

scenario 2

scenario 3

scenario 4

scenario 5

Figure 7.4 Hydrograph in Geul near Meerssen for the five scenarios, for the period 93b

The timing and location of the discharge (m³/sec) and the level (m) of the water flowingthrough the Geul river and its tributaries were simulated as a function of the water inflowcalculated in the hydrological study of Chapter 6. This water inflow was calculated forfive different scenarios reflecting different land use measures applied in the uplands ofthe catchment area. Consequently, the discharge and the level of the water flowingthrough the river canals varied as a function of the different land use scenarios. The landuse options aimed to retain water in the uplands and to reduce the (peaks) of waterinflow into the river network. Hydraulic infrastructure devices were installed in the rivercanal in two of the five scenarios. These aimed to retain water in the upstream parts ofthe river. The maximum water level (m), simulated per scenario, is plotted on alongitudinal profile of the Geul river relative to the height of the riverbanks. Analysis ofthe profile allowed concluding on where the flood-prone areas are located and whichscenario is most favourable to reduce the risk of flash flood events.



Scenario 1 and 5 reflect the current- and historical discharges (taking into accountmodifications of land use, but neglecting modifications of the river bed). They differ by 4to 7% (as obtained in the hydrological study). Simulated water heights differ, on average,by 10 cm (maximally 22 cm) and exceed the height of the riverbanks for both situations.

0

5

10

15

20

25

30

35

40

45

6120 6145 6170 6195 6220 6245 6270 6295 6320 6345

WLPH��KRXUV�


scenario 1

scenario 2

scenario 3

scenario 4

scenario 5

Figure 7.5 Hydrograph in Geul near Meerssen for the five scenarios, for the period 98

Scenario 2 hardly reduces the risk and effects of flash flood events. Covering thesteepest slopes with grassland does not ameliorate the risk of flooding compared to thecurrent reference risk. This is also true when the floodplain roughness is increased byinstalling bushes in the floodplains as a hydraulic device.

Scenario 3 implies all steepest slopes to be afforested. This reduces the risk of floodingclose to the historical land use reference risk.

Land-related measures of scenario 4 imply the re-introduction of green belts orhedgerows in cultivated farmland, and lead to the same results as scenario 3. Theconstruction of constriction devices (e.g. orifices and pipes) to create retention basins inthe upstream parts of the river system significantly affects and reduces the risk of flashflood events. The large peaks in water discharge are attenuated and delayeddownstream of these hydraulic constructions.



Scenario 4 cannot guarantee the complete prevention of flooding. Local flooding zonesare identified by means of the calculations; notably near mills along the river. Theseflooding problems have to be solved locally.

Finally, land use related measures do not significantly reduce the peaks in river waterheight below the height of the riverbanks. The risk of flooding is therefore notsignificantly reduced. A reason is that the proposed land-related measures affect onlypart of the cultivated farming land. If the involved acreage was bigger, for instance grassor afforestation on slopes steeper than 6 or 8%, the effect of the land use transformationwould be higher.3 Anyway, the transformation of cultivated steep slopes into pasturelandor forest could have a positive effect on local bottlenecks.

The creation of upstream water basins by introducing constriction devices in the rivercanal, combined with land-related measures, does significantly ameliorate the situation.The peaks in river water discharge are reduced and the maximum river water heightsare generally below the riverbanks, contrary to all other scenarios. (see Annexe G)

3 This is perhaps shown in scenario 4, where already half of the farming land was transformed in grassland(‘introduction of green belts’), with a resulting larger runoff reduction.


Legal Framework 106

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Whenever a particular measure is considered to be effective, appropriate instruments,such as laws or regulations, are required to implement the measure. This chaptersummarizes the legal instruments, or the framework, for implementing measures withinenvironmental and water management policy and legislation. The objective was toanalyse the compatibility and conflicts between recommended flash floods reducingmeasures and the current legal framework. This analysis could be the starting point forimplementing these measures.

An inventory of legal instruments was made for both Belgium and the Netherlands on anational, or regional, provincial and local level. As the Belgian part of the Geul catchmentbasin is located in both the Walloon Region and in a small part of the Flemish Region, adistinction was made between these two regions. Attention had to be paid to thedifferences between the Dutch, Walloon and Flemish legal framework because thesedifferences are the basis for different approaches in dealing with the current floodingproblems.

In this chapter, the legal framework and policy instruments are presented for theNetherlands, the Flemish region and the Walloon region. The studies for the threeregions are discussed separately. Each time the inventory is compared against somepossible flash floods reducing measures as proposed for during the scenario-developingphase in this pilot study. This comparison is presented in an applicability matrix in orderto gain an easier insight in the possibility of, or problems concerning, measureimplementation. A brief comparison between these applicability matrices is made in theconclusions.

At this stage, in view of the pilot character of the study, the considered measures are notassessed on their territorial applicability in the Geul catchment basin. They are notconsidered on a plan-level; only the legal applicability is taken into account. However, toimplement in practice a measure or a set of measures, a ‘full’ assessment must takeplace. Both the legal, technical and territorial applicability must be considered, as well asthe social acceptance and the costs involved. The measures must be balanced withrespect to the specific territorial characteristics of the catchment area. For a successfulimplementation it is of crucial importance that all involved parties, especially the landusers themselves, are convinced of the impact and use of a particular measure. Forinstance, some of the measures can only be implemented on a voluntary basis. Inaccordance with the current project, the ecologically sound and sustainable character ofa chosen measure must - of course - be obvious.


Legal Framework 107

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8.2.1 Actors in the Dutch institutional legal framework

The following institutions and organizations are responsible for handling flooding anderosion problems in the Dutch part of the Geul river catchment:

• The Province of Limburg

• The Waterboard “Roer & Overmaas”

• Municipalities

• The agricultural sector

• Land Development Commissions

The Province of Limburg defines and supervises the tasks of the Waterboard, themunicipalities, and the Land Development Commissions. The policy of the Province ofLimburg aims at reducing the flooding problems to an acceptable level by introducingstructural measures. Measures concerning nature development, land cultivation andinfrastructure measures need to be combined and attuned. Provincial policy has astrategic character. The province draws up a strategic framework and the main generallines of policy. Other policy levels should implement the elaboration and realisation ofappropriate measures.

One of the most important authorities with respect to water management is theWaterboard “Roer en Overmaas”, which is responsible for the operational policy andmanagement regarding flood protection and water quantity in the South and Middle ofLimburg.

The water management at municipal level (the local public works department) is limitedto managing sewerage systems. A municipality also has an important task with respectto land use planning; they are responsible for the land use planning between themunicipal borders.

The agricultural sector consists of all agricultural institutions and (private) organisations.The local farmers are important stakeholders in water and erosion problems. The LLTB(Limburgse Land en Tuinbouw Bond), which is an agricultural union, is responsible formaintaining relevant agricultural regulations.

Land Development Commissions represent public and other interested organisations inregional land development projects. These land development projects aim at improvingconditions for agricultural production, at the protection and development of landscapeand nature, and at the set-up of recreational facilities. There are three land developmentprojects and three corresponding Land Development Commissions in Southern Limburg:(1) Mergelland, (2) Mergelland Oost, and (3) Centraal Plateau.

Annexe F.2 gives a more detailed description of the Dutch institutional framework withrespect to the current problems in the Geul catchment.


Legal Framework 108

8.2.2 Instruments

The considered policy levels each have their own legal and political instruments to dealwith flooding and erosion problems (Table 8.1). As for the Dutch part of the catchment,the inventory has been made on a (1) national, (2) provincial and (3) local level. AnnexeF gives a more detailed description of each instrument.

Table 8.1 Inventory of the relevant Dutch legal instruments

1DWLRQDO�OHYHO

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This is a joint declaration among the French, German, Belgium, Luxembourg and Dutch Ministers ofEnvironment in which they state the need to reduce flood-related risks as rapidly as possible byfocusing on water retention in the Meuse River catchment.

µ$0Y%�H[�DUWLNHO��:HW�ERGHPEHVFKHUPLQJ¶�RU�DQ�RUGLQDQFH�IROORZLQJ�WKH�6RLO�3URWHFWLRQ�$FW

The Dutch Soil Protection Act could provide a basis for an AMvB4 (an implementing regulation orordinance) that aims at reducing erosion problems. The AMvB is a national instrument to beestablished by the minister himself.

)RUHVWU\�3ROLF\�3ODQ

The Forestry Policy Plan outlines the national forestry policy. It sets the framework for the provincial(regional planning) and municipal policies (zoning plan).

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The /DQGERXZVFKDSVYHURUGHQLQJ of the Dutch Agricultural Board in The Hague (+RRIGSURGXNWVFKDS$NNHUERXZ) is applicable to erosion-sensitive farming land in Southern Limburg. It contains certainregulations for the cultivation of the most erosion-sensitive grounds.

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The Province of Limburg defines its policy with regard to land use planning5 in the 6WUHHNSODQ. Ittranslates the national policy into regional policy and it sets the framework for local authorities.

µ3URYLQFLDOH�:DWHUKXLVKRXGLQJVSODQ¶�RU�3URYLQFLDO�:DWHU�0DQDJHPHQW�3ODQ

This plan outlines the provincial policy, the functions of the water systems, the desirabledevelopments, functioning and protection of the systems.

3URYLQFLDO�5HJXODWLRQ

Based on the Environmental Protection Act and the Water Management Act, the Province of Limburghas the possibility to introduce new regulations to deal with the considered flooding and erosionproblems. Until now the province did not use this possibility. It has been satisfied with the erosionregulation introduced by the agricultural sector itself.

$JULFXOWXUDO�0DQDJHPHQW�$JUHHPHQWV

The ‘agricultural management agreements’ in the Dutch Agricultural Law aim at government imposed

4 AMvB is the abbreviation for ‘$OJHPHQH�0DDWUHJHO�YDQ�%HVWXXU’.5 Land use planning, in Dutch known as ‘5XLPWHOLMNH�2UGHQLQJ’.


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management and land use planning which allow agricultural development and conservation of scarcenatural areas to co-exist.�The province determines which areas are to be assessed as managementareas, as nature development areas or as nature reserves.

/RFDO�OHYHO

:DWHU�0DQDJHPHQW�3ODQ

The Waterboard Roer and Overmaas and the =XLYHULQJVFKDS Limburg (Purification Board) give theirvision on water quantity and quality in the Water Management Plan. The plan serves as a guideline forthe Waterboard’s water-resources management.

7KH�µ.HXU¶�RU�:DWHUERDUG�2UGLQDQFH

One of the most important competences of the Waterboard is the possibility to issue byelaws that arenecessary for the management of their assignments. By this they can force a third party to act in thepreferred way. The Waterboard Ordinance or so-called “Keur” aims at the protection of water worksand riverbeds by regulating third parties.

=RQLQJ�SODQ

Each municipality gives its view on the local land use planning through a zoning plan. The plan is aframework for the examination of the potential and current land use.

/DQG�'HYHORSPHQW�3ODQ

Land development projects aim at improving the conditions for agricultural production and theprotection and enhancement of the landscape, nature and recreational facilities. For each project, acommission, representing members of public and regional institutions or actors, establishes a landdevelopment plan. The projects are sponsored at national policy level.

0DQDJHPHQW�$JUHHPHQWV�IRU�VPDOO�VFDOH�ODQGVFDSH�HOHPHQWV

Landowners have the opportunity to make an agreement with the Dutch government concerning themaintenance of small-scale landscape elements on their farmland (e.g. green belts, wood). Theprovincial Council IKL (‘6WLFKWLQJ�,QVWDQGKRXGLQJ�.OHLQH�/DQGVFKDSVHOHPHQWHQ’) is responsible for theexecution of this regulation.

Another important development in the considered region is the establishment of a“Declaration of Intent”. The Province of Limburg, the Waterboard, the municipalities ofSouthern Limburg, the LTTB and the three Land Development Commissions recentlyundersigned a declaration of intent which aims at strengthening the approach in dealingwith erosion and water problems, e.g. the institutions have to be empowered to be ableto enforce local regulations. The Declaration will be embodied in a covenant and in animplementation programme.

8.2.3 The applicability matrix

The applicability matrix (Table 8.2) compares the instruments as mentioned in part 8.2.2against several potential flash floods reducing measures (potentially applicable technicalmeasures, simulated in Chapter 6 and 7). The matrix gives an idea about the relevanceand the applicability of each instrument with respect to water retention purposes.


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A distinction was made between instruments which are: (�) applicable (already enforced– symbol used in the applicability matrix is ‘�’), (�) possibly applicable (needs furtherinvestigation and elaboration – symbol used in the matrix is ‘�’), (�) not applicable (cannot be used in this framework – QR�V\PERO in the applicability matrix), (�) instrumentswhich are not meant for water retention purposes at first, but which could have anindirect positive effect on flash floods reduction while being used for another purpose(symbol in the matrix is ‘L’) and (�) instruments which are available for protectionpurposes (the instrument can contribute to the prevention of flooding problems – symbolused in the matrix is ‘S’). The matrix also indicates the time frame over whichinstruments could be used to implement a measure; a distinction was made betweenshort term (0-5 years), middle long term (5-10 years) and long term (10-15 years). Theavailability of financial resources and whether usage of the instruments is based on avoluntary basis are also indicated.

The outcome of the applicability matrix will be discussed in the next paragraphs.

8.2.3.1 National level

The Declaration of Arles, the land use planning policy (Regional Planning), and theProvincial Water Management Plan can be used as sensitisation instruments in the flashfloods issues. These instruments are highly valued since recognition of floodingproblems on both international and local policy levels is a prerequisite in handling them.

The other two instruments at national level, the ‘AMvB’ and the Forestry Plan, are lessapplicable to water retention purposes. An AMvB, in this case based on the SoilProtection Act, is a very powerful instrument and is not commonly used to reduce ORFDOproblems. However, if such an instrument is applied, land use regulations aimed at soilprotection and the reduction of erosion problems may be promulgated.

The ‘/DQGERXZVFKDSVYHURUGHQLQJ’ of the Dutch Agricultural Board is a land useregulation already being applied to protect farmland against erosion. The policy isformulated at national level and forms the framework for measures at local level. Theapplicability of this regulation depends on the slope, or gradient, of the farmland. Theregulations vary from imposed agricultural techniques in the autumn, for instance theintroduction of ground cover, and adjustment of parcels, to the recommendation to turnhigh sloping parcels into grassland or wood. Such sustainable measures can have amajor impact in dealing with the current erosion problems. Thus, the‘/DQGERXZVFKDSVYHURUGHQLQJ’ is not primarily aimed at water retention; but waterretention may well result from these land use regulations.

The same applies to the national Forestry Plan. The plan is applicable to water retentionpurposes on an ad hoc basis. Water retention can be considered as a spin-off of forestrymanagement, whereas water retention is not the main objective of, or reason for theseplans.


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Table 8.2 Applicability matrix of Dutch policy instruments versus technical measures

0HDVXUHV��,QVWUXPHQWV

Dec

lara

tion

of A

rles

AM

vB S

oil P

rote

ctio

n A

ct.

For

estr

y P

olic

y P

lan

Ero

sion

reg

ulat

ion

Reg

iona

l Pla

nnin

g

Pro

vinc

ial W

ater

Man

agem

ent P

lan

Pro

vinc

ial r

egul

atio

n

Land

Dev

elop

men

t Pla

n

Agr

icul

tura

l Man

agem

ent A

gree

men

ts

Agr

eem

ents

for

man

agem

ent o

f lan

dsca

pe e

lem

ents

Zon

ing

plan

Wat

er M

anag

emen

t Pla

n

Wat

erbo

ard

Reg

ulat

ions

Policy of sensitisation and awareness-raising + + + +

Incentives policy + i i

Adjustment of riverbed 0 + p + +

(Re-)allocation of the riverbed 0 + p + +

Creation of wetlands 0 + i p + +

Ground cover and limited fallow 0 + 0 0

Turn high sloping areas to grassland/wood 0 i + + i p

Re-introduction of hedgerows/green belts 0 0 + i i p + +

Principles of sustainable farming 0 +

Land retirement i 0 p

Adjustment of parcelling 0 + + 0

Storage basin (river/upstream) 0 + p + +

3HULRG (l=long; s=short; m=middle longterm) s l m s m m s m/l s s s/m m s

)LQDQFLDO�UHVRXUFHV (y=yes; n=no) y n y n y y n y y y y y y

9ROXQWDU\ (y=yes; n=no) n n n n n n n n y y n n n

8.2.3.2 Provincial level

The Regional Planning and the Provincial Water Management Plan are more or lessstrategic instruments. They mainly outline the current functions of the area (recreation


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area, nature reserve etc.), the desirable function development and the functioning andprotection of the water systems. As mentioned before, it is quite essential to recognisethe current flooding problems during the formulation phase of these plans. Already theseinstruments play an important role with respect to policy aimed at sensitisation.

The Province could issue its own flash floods reducing regulations. From an uni-directional environmental point of view this would not satisfy the current needs, becausethe Environmental Protection Act has no real basis for agricultural or land useregulations aimed at water retention. From a water managerial point of view, the floodingcan be dealt with by the Water Management Act. However, such provincial regulationswould not be very practical since the Waterboard already is authorized to introduce thiskind of regulations based on its ‘.HXU’.

Although the agricultural management agreements are not primarily aimed at waterretention purposes, they will contribute indirectly to this objective (i.e., with financialsupport) for turning high sloping areas into forests and the creation of wetlands.

8.2.3.3 Local level

The Water Management Plan of the water manager, Roer and Overmaas, and thePurification Board of Limburg is, or could be, the basis for concrete action in the Geulcatchment; for instance in case of adjustment and (re-)allocation of the riverbed, creationof wetlands, introduction of hedgerows or green belts and the construction of storagebasins. The time schedule for the introduction of these measures depends on severalfactors, such as the availability of financial resources and free land. The ‘.HXU’ of theWaterboard plays an important role in the protection of the water works and riverbeds,for it allows the Waterboard to put third parties under the obligation of sustainable water-resources management.

A zoning plan can play an important role with regard to the protection against floodingand water erosion by encouraging the introduction of small-scale landscape elements,limiting the paved surface area, prohibiting the conversion of grassland into farming landwithout licence, and allocating and protecting green belts, water ways and storagebasins.

The Land Development Plan is a promising instrument. It already is and could be thebasis for several measures aimed at water retention purposes. Unfortunately, theinstrument also has some disadvantages: (1) it is time-consuming, (2) it is inflexible and(3) the financial resources on national level are limited.

The Management Agreements for landscape elements can be applied to themaintenance of landscape elements such as hedgerows and green belts.

8.2.4 Conclusions on the Dutch legal framework

The considered actors have several policy instruments at their disposal that alreadyplay, or could play, an important role in dealing with current flooding problems. Theinstruments are multilateral and have been found in many policy sectors (environmental


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planning, land use management, agriculture…). An important conclusion is thatinvolvement and initiative of DOO these sectors is decisive.

As one could see in the applicability matrix, no major conflicts have been found betweenthe available instruments and the potential measures. Each measure can be supportedor initiated by at least one instrument. Unfortunately, most of the current instruments arenot aimed at reducing flooding and erosion problems. Nevertheless, they often have orcould have an indirect positive effect. For instance the Erosion Regulation is a typicalexample of such an instrument. Limitations of the instruments are also due to factorssuch as limited financial resources and limited possibilities to claim land.

The water management plans and the ‘.HXU’ regulation, both of the Waterboard Roer enOvermaas, the land development plans of the Land Development Commissions, thezoning plan of the several municipalities, and the Erosion Regulation of the AgriculturalBoard, currently offer the best opportunities to deal with the flooding problems.

There still is some uncertainty about the applicability of several instruments. For instancethe Erosion Regulation, of which the applicability does not only depend on the legalpossibilities, but also on the willingness of the authority or institute in charge.Cooperation is often required for the implementation of an instrument, but also for furtherinvestigation of the potency of the instruments.

8.2.5 Recommendations

The responsibility for dealing with the current flooding problems, and the possibility to doso, is wide spread among all stakeholders. Cooperation is therefore critical. The recentlyundersigned “Declaration of Intent” is a good starting point for the new integral approach.The participants have committed themselves to taking concrete action against flooding inthe Geul river region.

The Province of Limburg plays the key part in dealing with the flooding problems. Thepolicy and implementation of instruments is best co-ordinated at this level. It is quiteessential that the current policy regarding water retention becomes well applied in allother provincial plans too. This is even more important since the Province has decided todraw up an Environmental Plan. Furthermore, the provincial policy is to be guiding andshould be elaborated on local municipal level. It is recommended that the Provinceevaluates whether this can be actually done.

The provincial role in the Land Development process is a good example of theimportance of its position in combating the flooding problems. Many measures aimed atreducing the risk on flash floods can and need to be taken by the Land DevelopmentCommission. As the implementation of a Land Development project is rather time-consuming, a precise co-ordination of the process is crucial.

In addition, the Land Development Commission declared in a covenant to introduceappropriate measures (as mentioned earlier) and to co-operate when accelerated andtemporary measures preventing flash floods need to be established. The municipalitieswill also co-operate by offering the opportunity to adjust the current zoning plans in casea desired measure is to be implemented.


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The Waterboard will have to continue taking operational measures aimed at sound waterquantity management, as it has no authority to introduce agricultural or cultivationmeasures right now. The Waterboard could investigate the potential effect of the so-called ‘.HXU’ with respect to the flash floods prevention.

Another option is to look for possibilities to incorporate an additional regulation aimed atwater retention in the current Erosion Regulation. This possibility depends on thewillingness of the agricultural sector to co-operate. In the worst case, the Province ofLimburg needs to define its own regulation, specifically aimed at water retention and theprevention of flash floods in the region. By the end of 1999, the effectiveness of theErosion Regulation will be evaluated. In case the results fall below expectations, it wouldbe wise to reconsider this form of regulation and the current fleshing out system.Anyhow, close cooperation with the LTTB (the agricultural union) is crucial for themaintenance of the Erosion Regulation.

Furthermore, the Waterboard should play a central part in propagating a progressivevision; with among other things a focus on water retention in all Land Developmentprojects.

�� %HOJLXP

Belgium is a federal state that consists of communities and regions. The decision-making power in Belgium is no longer exclusively in the hands of the FederalGovernment and the Federal Parliament. The management of the country falls to severalpartners, which exercise their competences independently in different fields.

The redistribution of power followed two broad lines. The first concerns linguistics and,more broadly, everything relating to culture. It gave rise to the Communities, a conceptwhich refers to the persons that make them up and to the bound that unites them, in thiscase language and culture. Belgium has three Communities today, based on language:the Flemish Community, the French Community and the German-speaking Community.These correspond to population groups. The second main line of the State reform ishistorically inspired by economic concerns, expressed by regions which claimed moreautonomous power. This gave rise to the founding of three regions: the Flemish Region,the Brussels Capital Region and the Walloon Region.

In this Geul project we do not consider the %HOJLDQ legal framework, as the federal stateBelgium does not retain any important competence concerning the reduction of theflooding risk in the Geul catchment. The federal state Belgium empowered the Regionsto implement the environmental policy (for instance the environmental planning,protection of the environment, water-resources management, land use planning,environmental and agricultural aspects of the European agricultural policy).


Legal Framework 115

�� 7KH�)OHPLVK�5HJLRQ

A small part of the Geul catchment is located in the Dutch-speaking part of Belgium. Wepoint at the river Gulp, a tributary of the Geul, which flows for about 5.1 km throughVoeren, a small part of the Flemish Province of Limburg. The Flemish Gulp is a naturalmeandering river with five tributaries worth mentioning: the Bachbeek, the Teuvenbeek,the Sinnichbeek, the Remersdaalbeek and the Mabroekbeek on the Flemish-Walloonborder.

8.4.1 Actors in the Flemish institutional legal framework

8.4.1.1 Regional level

All administrative services of the Flemish Region and the Flemish Community areconcentrated in one ministry, the Ministry of Flanders. The Ministry consists of severalDepartments, each divided up in Administrations, which, at their turn, consist ofDivisions. For this project we are mainly interested in the policy of one department: theEnvironmental and Infrastructure Department (LIN)6. Most environmental competencesin Flanders are embodied in this LIN Department. We will focus on two LINAdministrations, namely AMINAL7 and AROHM8, each divided up in several Divisions(e.g. AMINAL Water, AMINAL Land, AROHM Land Use planning). At this point we canalready mention the administrative distinction between the Flemish environmentalcompetences and the competences concerning land use, or ‘town and country’,planning. This distinction can handicap the implementation of solutions to such problemsas the Geul flash floods.

The Flemish Region also allotted some institutions, societies and companies - which arenot really part of, but depending on the Ministry - with specified environmentalcompetences. We mention the VLM9 with, among other things, competences regardingthe management of the Flemish manure surplus (the manure bank or ‘0HVWEDQN’) andre-allotment or land consolidation affairs.

Besides the LIN another Department of the Ministry of Flanders also holds importantstakeholders: the EWBL10 Department, or the department entailing Economy,Employment, Internal Affairs and Agriculture. The Division ‘Municipalities and Provinces’of the EWBL Administration ‘Internal Affairs’ is responsible for subsidising public worksperformed by local governments (e.g. sewerage works). The Administration ‘Agricultureand Horticulture’ pursues the Flemish agricultural policy, which for instance influences

6 LIN is the official abbreviation for ’Leefmilieu en Infrastructuur’, or Environmental and InfrastructureDepartment.7 AMINAL is the official abbreviaton for ’Administratie Milieu-, Natuur-, Land- en Waterbeheer’, or theAdministration for Environmental, Land and Water-resources Management.8 AROHM is the official abbreviation for ’Administratie Ruimtelijke Ordening, Huisvesting en Monumenten enLandschappen’ and is among others involved in land use planning affairs.9 VLM is the official abbreviation for ‘Vlaamse Landmaatschappij’, or a companysociety handling for all landaffairs concerning land and land use in Flanders.10 EWBL is the abbreviation for ‘Economie, Werkgelegenheid, Binnenlandse Aangelegenheden en Land- enTuinbouw’.


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the manure issues. This Administration is also responsible for subsidising agriculturalland use aimed at erosion-reduction.


There are no environmental competences specific to the provinces. However, theFlemish environmental legislation does charge the provinces with many administrativetasks, mainly concerning the permit-granting procedure. What’s more, the ProvincialCouncil can show autonomous legislative power in issuing byelaws(‘SROLWLHYHURUGHQLQJHQ’) concerning public health, security and order. A double restrictionis yet imposed on this legislative power:

- The Province can act constitutively if a municipality is unable to ensure the decentsettling of a local problem.

- The Province has statutory powers LI� DQG� RQO\� LI the subject cannot be settleddecently by federal or regional regulations.

The Watercourses and Territory Section of the Infrastructure Division and theEnvironment and Nature Division, both part of the Third Directorate of the FlemishProvince of Limburg, are the most important actors at this level.

The Watercourses Section is the executive office concerning unnavigable watercourses,and actively involved in the design of municipal water-management, or water-control,works.

The water-resources policy of the Province of Limburg does focus on:

1. flooding prevention

2. discouraging all accelerated surface water runoff

The Provincial authorities specifically emphasise the prevention and reduction of surfacerunoff on the slopes in the Gulp catchment. According to our informants of theWatercourses Section, the Gulp and Geul flooding problems are especially caused bythe natural relief, which points the flooding problems to the Agricultural Section as well.

8.4.1.3 Local level

As stakeholders at local level we mention the farmers themselves, the µ%RHUHQERQG¶, anagricultural union, and the city of Voeren with an Agricultural and Environmental Board.

Flemish municipalities have a triple environmental competence:

- As for the provinces, the federal and regional environmental legislation does chargethe municipalities with many tasks, for instance concerning the environmental permit-granting procedure, concerning land use planning (the so-called ‘SODQQHQ� YDQDDQOHJ’) etc.


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- Municipalities can act constitutively by issuing byelaws concerning public health,security and order. These municipal statutory powers can only be used in mattersthat have not been consigned by law or decree to a higher level of government(province, region, state).

- The Chief of Police is an officer of the ‘judicial police’ as well. Therefore he isauthorised to trace and record all offences against the environmental legislation.Municipal policemen have booking authority.

In the following part we will give an overview of the relevant Flemish regulationsconcerning flash floods prevention and restriction. The policy domains of interest are thewater-resources management, the environmental policy, the policy concerning land useplanning and the agricultural policy. The instruments will be briefly described in part8.4.2 before being validated in the next part.

8.4.2 Instruments

8.4.2.1 Water-resources management

1. Declaration of Arles (cf. part 8.2.2 in the Dutch legal framework)

2. Basic law concerning the unnavigable watercourses: ‘:HW��EHWUHIIHQGH�GH�RQEHYDDUEDUHZDWHUORSHQ¶

3. Basis for police regulations concerning unnavigable watercourses: ‘.RQLQNOLMN� %HVOXLW� YDQ� �DXJXVWXV� �� %�6�� KRXGHQGH� DOJHPHHQ� SROLWLHUHJOHPHQW� RS� GH� RQEHYDDUEDUHZDWHUORSHQ’

4. Provincial regulation concerning the unnavigable watercourses

5. Provincial subsidy scheme: ‘3URYLQFLDDO�VXEVLGLsULQJVEHVOXLW’

6. Decree with regard to dikes and dams: ‘'HFUHHW�YDQ��DSULO��%�6��EHWUHIIHQGH�GHZDWHUNHULQJHQ’ and implementing orders

7. Principles of good practice regarding the Flemish sewerage system: ‘.UDFKWOLMQHQ� YRRU� HHQJHwQWHJUHHUG�ULROHULQJVEHOHLG�LQ�9ODDQGHUHQ��’

8. Preliminary decree ‘Integral Water-resources Management’: ‘9RRURQWZHUS� YDQ� GHFUHHW� WRWDDQYXOOLQJ�YDQ�KHW�GHFUHHW�YDQ��DSULO� ��KRXGHQGH�DOJHPHQH�EHSDOLQJHQ� LQ]DNH�PLOLHXEHOHLGPHW� WLWHOV� EHWUHIIHQGH� KHW� LQWHJUDDO� ZDWHUEHKHHU�� RSSHUYODNWHZDWHUNZDOLWHLW�RSSHUYODNWHZDWHUNZDQWLWHLW��JURQGZDWHU�HQ�ZDWHUYRRU]LHQLQJ��’

9. Water management plans: ‘ZDWHUKXLVKRXGLQJVSODQQHQ’

For the Flemish Region, the basic law of 1967 has been supplemented with the Decreeof 1983 regarding the clearing of unnavigable watercourses.11 Among other things, thelaw identifies three categories of unnavigable watercourses and assigns the managersof each category. 11 ‘Decreet van 21.04.83 houdende de ruiming van onbevaarbare waterlopen.’


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The Gulp river and the Mabroekbeek are classified watercourses of second category;the Bachbeek, the Teuvenbeek, the Sinnichbeek and the Remersdaalbeek are classifiedas third category. The Gulp river and its tributaries do not belong to a territory managedby a ‘Polder’ or ‘Wateringen’ Board.

Clearing, maintenance and restoration works on unnavigable watercourses of secondcategory are performed by the provincial government. Municipalities are responsible forthe management of unnavigable watercourses of third category. All activities onwatercourses of second and third category have to be performed according to the‘Provincial regulation concerning the unnavigable watercourses’. Provincial officials havepolice competence on the unnavigable watercourses of second and third category, andon the non-classified unnavigable watercourses.

Some extra-ordinary water management activities12 need a construction licence, andsome need a MER13, an environmental impact assessment, as well (regionalcompetence – fitting in with the legislation on Land Use Planning). The requirement of aconstruction licence or a MER depends, among other things, on the water-managementworks taking place in particular ‘zones’ of the Flemish ‘JHZHVWSODQ’,�or regional plan (forinstance areas identified as nature area or reserve, area of important ecologicalvalue…). As for a storage basin, a MER is required from a surface area of 50 ha on.

Provincial authorisation is required for the execution of all extra-ordinary improvementor/and adjustment works on unnavigable watercourses of second and third category.This authorisation has to be granted by the ‘%HVWHQGLJH� 'HSXWDWLH’, the PermanentDeputation, of the Province of Limburg (provincial competence).

The Province subsidises all local water-management works up to 20% of the total cost.According to the ‘Provincial subsidy scheme’ expropriation of privately owned land,which is necessary for the construction of a storage basin, can also be subsidised. Sucha storage basin does not need to be on the watercourse itself: an upstream basin can besubsidised as well. Even green belts along the watercourse, with enough hydraulicimpact on the watercourse and providing additional storage capacity, can be consideredfor subsidisation. The Province can also purchase the land necessary to restore thenatural meandering of a watercourse. Of course, this is not relevant for the Flemish Gulpand its tributaries since these watercourses never have been adjusted.

The decree regarding 'dikes and dams' empowers the Flemish government toexpropriate privately owned real property along the watercourse for the sake of thepublic welfare: e.g. for the construction of dams, for flood control reservoirs, storagebasins and access roads. This expropriation competence also applies for the restorationof natural floodplains. As for the unnavigable watercourses this expropriation possibilityis restricted to watercourses of first category.

12 as opposed to the ordinary clearing, maintaining and restoration.13 MER is the official abbreviation for ‘Milieu Effecten Rapportering’, or a report considering all possibleenvironmental impacts of a certain activity (Environmental Impact Assessment – EIA).


Legal Framework 119

We do mention the sewerage policy, ‘Principles of good practice regarding the Flemishsewerage system’, because of its sensitisation relevance. The principles aim atrestricting the precipitation runoff (e.g. maximum disconnection of the paved surfacerunoff and of the watercourses from the sewerage system; limits to overflow), atmaximum infiltration and at retarded surface water drainage via trenches. The seweragepolicy especially counts at local level. Of course, there is only little paved surface in theGulp valley.

A note including main action points (‘NUDFKWOLMQHQQRWD’) lays down the foundation for therealisation of the integral water-resources management in the Flemish Region. A water-policy, fitting in the environmental policy, is drawn up based upon these main actionpoints. On the level of one or more river basins, the integral water-resources policy isbeing accomplished through a river basin-management plan. The preliminary decree‘Integral Water-resources Management’ provides for the Flemish governmentestablishing a water-management policy and these river basin-management plans everyfive years. It also provides for binding planning terms and for the competences regardingthe three sub-plans (water-quality, water-quantity and geomorphologic structure). In theFlemish Region, a step forward towards the realisation of integral water-resourcesmanagement was made by means of this preliminary decree.

AMINAL Water establishes water-management plans, or the policy with regard to water-quantity. It has been assumed that the ‘new’ water-control works should be resultingfrom balancing all functions and objectives of the water-resources system. This will bebased upon the hydrological modelling of the catchment of unnavigable watercourses.All parties, or stakeholders, are involved in the planning phase through a local platform.The plans will not only focus on the water-control works, but also on the possiblebuffering of water in the valleys and on the reciprocity between water-resourcesmanagement and land use planning.

For the sake of completeness, all actors relevant to the water quantity management inthe Flemish Region are summarised in Table 8.3.


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Table 8.3 Actors relevant to the water quantity management

&RPSRQHQW�RI�WKH�:DWHU�UHVRXUFHV�V\VWHP 5HVSRQVLEOH�PDQDJHUV

SURFACEWATER QUANTITY

Navigable watercourses AWZ14, with separate divisions for:

• The Coast

• Upper Scheldt

• Sea Scheldt

• Meuse and Albertchannel

Unnavigable watercourses

(first category)

AMINAL

• The Water Division


(second category)

Province


(third category)

Municipality supervised by the Province


(non-classified)

Adjacent landowners

Watercourses located in ’Polders’ or’Wateringen’

Polder or Wateringen Board

GROUNDWATER QUANTITY AMINAL

• The Water Division

• The Permit Division

8.4.2.2 Land use planning

1. Decree concerning the land use planning in the Flemish Region: ‘'HFUHHW�KRXGHQGHGH�UXLPWHOLMNH�RUGHQLQJ�YDQ��PDDUW��%�6��KRXGHQGH�GH�EHNUDFKWLJLQJYDQ�KHW�%HVOXLW�YDQ�GH�9ODDPVH�5HJHULQJ�YDQ��RNWREHU��%�6��’

The decree introduces the master planning that has to be implemented at the threeFlemish policy levels. All three planning levels can provide for implementing ordinances.The Provincial and municipal planning levels can provide for compulsory directives aswell. The reader will find an overview in Table 8.4.

Municipalities have the possibility to issue so-called ‘building ordinances’, by which theycan impose a licence-requirement on certain – in itself licence-free – operations. Thiscan be important in case of interventions endangering small-scale landscape elements(e.g. wood cutting, small relief alteration, vegetation alteration...). 14 AWZ is the official abbreviation for ’Administratie Waterwegen en Zeewezen’, or the LIN administrationresponsible for the navigable waterways and marine management.


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AROHM Land Use planning co-ordinates and directs the actions of the local ROHMdivisions15 concerning their support in the land use planning process of the localauthorities.

Table 8.4 Land use planning in the Flemish Region

)OHPLVK�5HJLRQ 3URYLQFH 0XQLFLSDOLW\

:KDW RSV16 Provincial RS17 local RS18

:KR Flemish Government(i.e. AROHM Land Use

planning)

Provincial council Municipal council

,PSOHPHQWDWLRQ

*HZHVWSODQQHQ(regional planning)

Regional ordinances

3ODQQHQ�YDQ�$DQOHJ(layout planning)

(setout by the Flemishgovernment)

Provincial ordinances

(approbation by theFlemish government

needed)

APA’s19

BPA’s20

(amendments of themuncipal PA’s by the

Flemish government arenot uncommon)

Municipal ordinances

(approbation by theFlemish government

needed)

2. Law of 1962 concerning the organisation of the land use planning: ‘:HW�YDQ��$UW��KRXGHQGH�RUJDQLVDWLH�YDQ�GH�UXLPWHOLMNH�RUGH�HQ�VWHGHERXZ’

This article stipulates that the cutting down or digging up of straight timber (treesmeasuring one meter around at the foot of the trunk) has to be licensed by themunicipality.

3. Land consolidation and land development planning

Farmers usually ask for a land consolidation project. They ask for connected parcels,without barriers, in order to increase produce of their lands. First, expert-consultants willinventory all distinct elements in the considered parcels. Besides this inventory they willgive their opinion on, and perception of, the value of certain elements (e.g. on greenbelts, small-scale landscape elements) as well. A MER, an environmental impactassessment, usually has to be performed. The Land Consolidation Committee, togetherwith the VLM and all stakeholders involved, will draw up a landscape plan and a 15 AROHM has a field organization (called ROHM) in all Flemish provinces.16 This is the outline for the Flemish regional Master Plan and the abbreviaton for ‘5XLPWHOLMN�6WUXFWXXUSODQ9ODDQGHUHQ’.17 This is a master plan at provincial level, and RS is the abbreviation for ‘5XLPWHOLMN�6WUXFWXXUSODQ’.18 This is the master plan at the level of the municipality.19 The ‘$OJHPHQH�3ODQQHQ�YDQ�$DQOHJ’, or ordinary layout planning.20 The ‘%LM]RQGHUH�3ODQQHQ�YDQ�$DQOHJ’, or extra-ordinary layout planning.


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reallotment plan with adjusted parcel borders. AMINAL Land has to follow up the landconsolidation project.

The Province has to refund the Land Consolidation Committee for cleaning,maintenance and restoration works on unnavigable watercourses of second category.The Province advises on, and pays for, extra-ordinary improvement and modificationworks. The Province also advises on watercourses to be filled in or re-designed during aland consolidation project. Watercourses or ditches dug as part of a land consolidationproject do not require a construction licence.

Large connected parcels in a hilly region have some disastrous consequences: theyincrease soil erosion and accelerate the surface runoff. And this Geul-project preciselyaims at avoiding or restricting these two processes… Therefore land consolidationprojects always have to be linked to preconditions concerning sustainable land use (e.g.conservation or re-construction of green belts). Unfortunately, these conditions cannotbe enforced by this time being. They can only be implemented after giving adequateeducation. A maximum of 2% of the surface area, which was not used for farmingpurposes EHIRUH the land consolidation project, can be claimed for land or naturedevelopment measures. Our informants of AMINAL Water and the Province of Limburgdid mention the urgent need in the Flemish Region to reconsider land consolidationprojects at parcel-level and to link these projects with land development planning.

Land development planning usually covers a much wider area than the landconsolidation projects. The VLM, together with the Land Development Committee andmany stakeholders draw up the Land Development Plan. AMINAL Land follows up thisplanning phase. Once the Land Development Plan has been approved, theimplementation is left to third parties. The VLM has the possibility to subsidise a LandDevelopment Project by means of the ‘Land Development Fund’. Of course, thesesubsidies can only indirectly be used for runoff reduction.

The first land development projects are in progress; it concerns however small-scaledinterventions for now.

8.4.2.3 Land use and agricultural policy

1. Principles of sustainable farming: ‘&RGH�YRRU�JRHGH�ODQGERXZSUDNWLMNHQ’

The principles of sustainable farming are formulated with – among other things – theintention of combating the erosion problems at first, and are only indirectly aimed atwater retention. The farmers are the target group. They are approached directly, butunder no obligation to implement the principles.

By Order of the Flemish Government (Administration of Agriculture and Horticulture), theapplication of sustainable methods of agriculture can be subsidised. This Order followsthe European Ordinance 2078/92, which discusses the financial support for agriculturalmethods that are compatible with environmental protection and nature conservation. Forinstance, contour ploughing and maintaining ground cover during winter season are


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methods that could be subsidised21. Until recently no education or information sessionswere organised for the farmers. Consequently, they distrusted the proposed ‘new style’methods of agriculture.

Municipalities can issue a bye-law (a local ordinance) to enforce (some of) the principlesof sustainable farming in the context of erosion restriction or flooding prevention, e.g. thebye-law issued by the city of Aarschot, i.e. ‘*HPHHQWHOLMN�SROLWLHUHJOHPHQW�EHWUHIIHQGH�GHEHYHLOLJLQJ�WHJHQ�RYHUVWURPLQJ’.

2. Decree regarding the Flemish manure problem: ‘'HFUHHW� YDQ� �� WRWEHVFKHUPLQJ� YDQ� KHW� OHHIPLOLHX� WHJHQ� GH� YHURQWUHLQLJLQJ� GRRU� PHVWVWRIIHQ’ andimplementing orders

Among other things this decree regulates a manuring ban in the 5-meter zone,measured from the watercourse towards the land, along a watercourse.

3. Decree with regard to the protection of landscapes: ‘'HFUHHW�YDQ��RYHU�GHEHVFKHUPLQJ�YDQ�ODQGVFKDSSHQ’, and implementing order of 03.06.97 concerning thecultivation ban of everlasting grasslands.

This decree is valid in ‘agrarian regions of considerable natural beauty’.

4. The Forest decree, regulating the organisation and management of the Flemishforests

The Forestry division of AMINAL can subsidise the afforestation of farmland (byenforcement of the European Ordinance 2080/92). All owners of farmland can join,provided that their afforestation covers at least 0.5 ha.

8.4.2.4 Environmental policy

1. Environmental policy plan at regional level: ‘0LOLHXEHOHLGVSODQ��’ or MINA-plan 2

From 1997 to 2001 this plan is nothing less than the guideline for the Flemishgovernment to define its environmental policy. Each year, the Flemish governmentdraws up an environmental agenda (‘0LOLHXMDDUSURJUDPPD’) in order to implement theMINA-plan 2. This agenda indicates which part of the plan is implemented each year andalso contains a financial plan, which is added to the yearly budget-proposal of thegovernment. The MINA-plan 2 contains a ‘plan of action’, dealing with a number of topics(actual environmental problems). Within each topic, specific aims, strategies, actions orinitiatives are developed. Some actions are binding and financed; others non-bindingand not yet financed. A number of actions from the subjects ‘Dehydration’ and ‘Area-oriented approach’ are relevant for the Geul-project.

21 Europe and the Flemish Region each pay half of the subsidy.


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Amongst others dehydration is caused by a more rapid runoff of surface water, due tothe expansion of paved surfaces and due to certain water-control works.

The following actions are worth mentioning:

- Action 66: ‘Developing and improving policy instruments regarding land use.’

Land-usage should be geared to the water-resources system’s characteristics throughthe policy for land use planning. The action includes amongst others the drawing up ofcharts of floodplains (flooded areas), valley lands and areas where unnavigablewaterways can freely meander. The environmental (i.e. spatial) implications of themeasures to be taken must fit in with the RSV.

- Action 71: ‘Renewal of the legislation on water quantity management.’

The legislation on unnavigable waterways is still based on a narrow, obsolete view of thewatercourse. The current ‘basic law of 1967’ is still aimed at faster runoff. This action fitsin with the current view on integral water-resources management in the Flemish regionand proposes, among other things, a simplification of the current spread of competencesamong the various policy levels.

- Action 72: ‘Stimulating infiltration and local storage and slowing down surface waterrunoff.’

This is a binding action, proposing measures concerning the slowing down and storageof surface water, by constructing green belts along parcel-borders, roads and waterwaysand/or by means of storage basins and floodplains.

- Action 74: ‘Further development and application of environment-friendly technologiesregarding the organisation and management of waterways.’

The existing regulations (‘9DGHPHFXP�1DWXXUWHFKQLVFKH�0LOLHXERXZ�±�:DWHUORSHQ’) aresupplemented, if necessary adjusted. They are combined as “Main action points for theorganisation and management of unnavigable watercourses”, and Provinces,municipalities, Polder Boards and Wateringen Boards must conform to these. Additionalfunds are provided for. This action, however, is non-binding.

Among other things, QDWXUDO floodplains may be used in the implementation phase of thisaction.

A number of other important actions form part of the topic ‘Area-oriented approach’.

- Action 127: ‘Realisation of environmental objectives using lay-out planning (SODQQHQYDQ�DDQOHJ).’

This action puts first and foremost the link between environmental management andtown and country, or environmental, planning.

- Action 129: ‘Establishing a platform for integral water-resources management in theFlemish Region.’

This action is binding. It offers a link between land use planning and integral water-resources management by seeking to convergence of procedures and planning (e.g.


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land use planning could answer to the need of flooding by applying a construction ban inthe valleys with a risk of flooding).

- Action 130: ‘Establishing a river basin platform.’ (binding)

- Action 131: ‘Drawing up integral river basin-management plans.’ (binding)

- Action 133: ‘Making land development a fully-fledged tool.’ (binding)

Action 133 implies at least the creation of a fully-fledged legal framework for landdevelopment, with a far-reaching set of tools and feasible procedures. The current toolfor land development must be made more operational by increasing the feasibility of theprocedures and extending the set of tools and (financial) resources.

As a tool, the MINA-plan 2 is most suitable then for the development of a policy plan,which has to be elaborated in a number of actions and initiatives.

2. Environmental policy plan at provincial level: ‘0LOLHXEHOHLGVSODQ�/LPEXUJ��’

This environmental policy plan implements the regional MINA-plan 2 at the provinciallevel. It should therefore not contradict the regional environmental policy.

The current 0LOLHXEHOHLGVSODQ�/LPEXUJ mentions the problem of undesired flash floods inthe Limburg region. According to the compilers of the plan, there are two causes lying onthe basis of these floods: the rather steep slopes in the basin and the large amount ofpaved surface with sewers and overflows.

Some actions out of the Water section in the environmental policy plan can be applicablein the Geul project:

- Action 10: ‘Take flow control (reducing) measures.’

To prevent floods, the Province of Limburg proposes the introduction of storage basinsand the definition of natural flood-prone areas. Enlarging waterways (to widen ordeepen) is not desirable. Surface runoff is to be opposed to a maximum.

- Action 13: ‘Aim for meandering, establish buffer zones along waterways and developwaterway-accompanying ecosystems.’

Some other actions of the section ‘Area-oriented environmental policy’ are relevant aswell:

- Action 2: ‘Propose green modifications to the regional planning concerning streamvalleys.’

By this stream valleys can get the necessary planological protection. The basis for thenecessary green modifications to the regional planning already lies in the provincial RS(spatial master plan).

- Action 4: ‘Develop a purchase policy for bank strips along waterways.’


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The Province of Limburg draws up its own purchase policy for unnavigable watercoursesof second category and buys the bank strips. Problem areas, such as flood-prone areas,come first. Local municipal authorities get an allowance from the Province for thepurchase of bank strips along watercourses of third category.

- Action 8: ‘Set up a sustainable structure for the preservation and development of small-scale landscape elements (SLE)’

Examples of these SLE, as defined in the ‘nature decree’, are JUDIWHQ, orchards,vegetation on parcel borders, bushes and wood. The Province of Limburg regularlyorganizes sensitisation-campaigns concerning the preservation of these small-scalelandscape elements and there is also a special provincial subsidy regulation for it.

- Action 12: ‘Investigate the possibilities for ecologically sensible wood expansion.’

This means, among other things, the afforestation of erosion-sensitive slopes. This‘slope wood’ is examined in cooperation with AMINAL and the involved municipalities.

3. Environmental policy plan at municipal level

Municipalities too can draw up environmental policy plans. These plans must notcontradict the provincial and regional environmental policy plan.

4. Decree of 21.10.97 concerning the preservation of nature and the naturalenvironment: ‘'HFUHHW�YDQ��EHWUHIIHQGH�KHW�QDWXXUEHKRXG�HQ�KHW�QDWXXUOLMNPLOLHX’ or the ‘1DWXXUEHKRXGVGHFUHHW’ (nature decree) with first enforcement decreeof 23.07.98.

The nature decree defines, among other things, small-scale landscape elements(verges, trees, bushes, banks, JUDIWHQ or cultured (man-made) talus, hedges, wood,high-trunk orchards, vegetation on parcel borders...). *UDIWHQ are typical for the region ofVoeren. Especially the fourth part of the enforcement decree is of interest. It mentions alicense-requirement for modifying certain vegetation-types and for modifying SLE (e.g. aban on certain modifications; a license-requirement for modifying the vegetation incertain areas or zones of the regional plan, an obligation to report certain modifications(e.g. digging out and straightening of streams)). The license is applied for at, andgranted by, the municipal executive of the municipality, or – in some cases – by thePermanent Deputation of the Province.

The Flemish Government can, in the interest of preserving nature, close ‘voluntarymanagement agreements’ with the land users. A management agreement is anagreement with which the land user commits himself voluntarily to deliver a pre-determined performance for a certain period of time. This performance is aimed ataccomplishing a higher environmental quality than the basis-environmental quality. Thiscan be done by maintaining or developing certain nature-values, for payment of a pre-determined reimbursement. A performance can also exist in neglecting certain land useactivities, such as letting the acre weeds grow in parcel peripherals or borders, insteadof removing them.


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Management agreements are closed with the VLM, the Flemish Land Society, and arefirst of all meant for farmers, among other things with the view to this parcel bordersmanagement. The first management agreements between farmers and the Flemishgovernment can come into effect on January 1, 2000. AMINAL and the VLM supervisethe management agreements. The management reimbursements are paid half by theEuropean Union, and half by the Flemish Government. Management agreements do fitin with the European agricultural and environmental policy (European ordinances2078/92 en 1257/99). Provinces and municipalities too can close voluntary managementagreements with private persons. These management agreements are mainly focusedon linear and ‘point-like’ landscape elements (SLE) and on the presence of nature in thebuilt-up area. For instance municipalities can do so in the framework of a municipalnature development plan (*HPHHQWHOLMN� 1DWXXURQWZLNNHOLQJVSODQ� or GNOP). Amunicipality or province can also decide to raise the management remuneration, as paidby Europe and the Flemish Region, with 30% at the most.22.

The nature decree offers several opportunities for nature conservation. Performingnature development projects (QDWXXULQULFKWLQJVSURMHFWHQ) is one of them. It’s a means toplan an area or domain, of a certain land use type, with a view to nature preservation, -restoration or –development. The Flemish Government can introduce a naturedevelopment project in a chosen area, take measures and execute the necessary worksto implement these measures. The Flemish Region pays all costs for the preparationand execution of such projects. Although aiming at different objectives, the measuresoffered by nature development projects can be compared with the measures identified inland consolidation projects, improving agri- and horticulture in the considered region.Within the scope of a nature development project, water management works can beperformed, such as alterations to the riverbanks, or to the longitudinal- and crosssections of a watercourse (e.g. restoration of meandering), adjustment of water supplyand drainage, alteration of the water level etc. These works are aimed at restoring orcreating a specific habitat for certain plant and animal species; they are not aimed atflash floods reduction. However, increased water retention, and a decreased risk of flashfloods, can be realized as indirect effects.

The Flemish Region and the Flemish municipalities can obtain privately owned parcelsof land for reasons of nature preservation by expropriation for the ‘public welfare’.

5. Municipal nature development plan or GNOP

A municipality can draw up a nature development plan or GNOP in accordance with thecriteria of the ‘Municipal Environmental Covenant 1992-1996’. The municipality ofVoeren however did not undersign this Environmental Covenant; neither drew up anature development plan up till now.

22 Remunerations received on the basis of the European ordinances 2078/92 and 1257/99 may not exceed acertain sum per hectare.


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The applicability matrix (Table 8.5) compares the inventoried Flemish regulations andinstruments against potential flash floods reducing measures. The measures arevalidated for their water retention purpose at first; so the matrix can give an idea aboutthe relevance and the applicability of each instrument with respect to this waterretention.

A distinction was made between instruments which are: (�) applicable (already enforced– symbol used in the applicability matrix is ‘�’), (�) possibly applicable (needs furtherinvestigation and elaboration – symbol used in the matrix is ‘�’), (�) not applicable (cannot be used in this framework – QR� V\PERO in the applicability matrix) for theimplementation of the measure aimed at water retention, and (�) instruments which arenot meant for water retention purposes at first, but which have an indirect positive effecton flash floods reduction (symbol in the matrix is ‘L’). The matrix also gives an indicationabout the time frame over which instruments could be used to implement a measure; adistinction was made between short term (0-5 years), moderate long term (5-10 years)and long term (10-15 years). The availability of financial resources, and the use ofinstruments on a voluntary basis or not is also indicated.


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Table 8.5 Applicability matrix for the Flemish legal framework

H VXUHV� �, VWUXPH WV

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Policy of sensitisation & awareness-raising 0 0 + + + 0 0 0 i + + +

Incentives policy 0 0 0(i) 0 i i i i

Adjustment of riverbed 0 0 + + +

(Re-) allocation of the riverbed 0 0 0 + 0 0 + + + +

Creation of wetlands 0 + 0 0 + 0 +

Ground cover and limited fallow i i 0(i)

Turn high sloping cultivated areas to grassland/wood i i +(i) 0 0(i)

Reintroduction of hedgerows/green belts 0 0 0/i +(i) i + + + +(i)

Principles of sustainable farming i

Land retirement 0 0 0 0 i i i 0 + 0 0 0

Adjustment of parcelling i i 0(i)

Storage basin (river/upstream) 0 0 0 0 0 0 0 + 0 0 +

3HULRG (s=short; m=middle long; l=long term) s s s s/m m m s/m m/l s/m s s m m m s

)LQDQFLDO�UHVRXUFHV (y=yes; n=no) y y y y y y y y y n y y y y y

9ROXQWDU\�(y=yes; n=no) y n n n n n n n y n y n/y n/y n y

Until recently the Flemish water-resources management was not quite oriented towards‘water retention’. For instance, the ordinary maintenance and restoration works in thebasic law of ’67 are still meant to secure a fluent water flow. The extra-ordinarymodification and improvement works, however, can literally be interpreted as ‘to 23 At this point, the term ‘water-resources management’ covers the basic law of ’67 concerning unnavigablewatercourses; the provincial regulation concerning the unnavigable watercourses and the provincial subsidyscheme as mentioned in part 8.4.2.1.


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improve’ — and so, if necessary, even slow down — the flow. The Province of Limburgtherefore describes these improvement works as ‘DUUDQJLQJ� WKH�ZDWHU� IORZ� WR� SUHYHQWIORRGV’. For instance, the Province considers the development of floodplains and storagebasins as such extra-ordinary improvement works, which can be subsidised. However,whether or not slowing down the runoff still happens voluntarily within the framework ofthis legislation: there is no obligation included in the law of ’67. One can freely choosebetween locally storing the excess of water or enlarging the watercourse. Fortunately,there is a wind of change blowing through the water-resources policy right now. Thepreliminary decree on integral water-resources management, and some actions out ofthe regional environmental policy plan (MINA-plan 2) and out of the environmental policyplan of the Province of Limburg are good examples of the new approach. The readercan see the applicability matrix showing the ‘SRVVLEO\� DSSOLFDEOH’ symbol for theinstruments regarding water-resources management; for these instruments could indeedimplement a number of measures, but still need some re-orientation and elaboration atfirst. The MINA-plan 2 and the Limburg environmental policy plan already make a movein the right direction.

The ‘principles of good practice regarding the Flemish sewerage system’ are ideally tobe used as sensitisation instrument in making all stakeholders aware of the need of anenhanced storage capacity and water retention. The other water managementinstruments could also be used for this awareness-raising purpose.

The compulsory directives of the 5XLPWHOLMN� 6WUXFWXXUSODQ� 9ODDQGHUHQ (RSV) can beinvolved to preserve the available storage capacity in the river basin as far as possible.For instance, building along watercourses, and the granting of the necessary buildingpermits, should be strictly regulated. Another possibility to enhance the available storagecapacity is the (re)introduction of small-scale landscape elements (e.g. green belts) bymeans of these ‘compulsory directives’. The RSV does not yet show any bindingstipulations concerning water quantity management in itself.

Green belts along the watercourse, and green belts along the contour lines of acultivated slope, can be realized within land consolidation, land development projectsand nature development projects too. Specific stipulations are needed to make sure thatfor example ‘erosion sensitive locations’ get classified as ‘grass way’. Such classificationis at first aimed at erosion reduction; water retention is only considered as an indirect orsecondary effect. If a land development plan provides for grassed waterways, the landneeded has to be purchased by AMINAL Water or by the Province. Expropriation stillhappens on a voluntary basis. The introduction of green belts, or hedgerows, by meansof the implementation of these instruments will take a considerable amount of time. Theapplicability matrix shows a moderate long to long time frame. Green belts along awatercourse could also result, as an indirect effect, from the implementation of thebuilding ban following the manure decree.

Preservation and reintroduction of other small-scale landscape elements and micro reliefcan be established within the framework of a ‘new style’ land consolidation project aswell. This kind of measures is particularly aimed at erosion combating by, for instance,restricting the length of a slope. The adjusted parcelling will provide for enhanced waterretention as an indirect effect.


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Flood plains and flood-prone areas should be defined and demarcated in the regionalplanning process. Adjustments to the Flemish ‘JHZHVWSODQ’ (regional plan) may beneeded. For this, particular areas must be defined where all works and operations areforbidden or subordinate to rigid stipulations as long as the necessary measures toreduce the flooding risk are not taken. The demarcation and development of wetlandscan be established by implementing a land development or land consolidation project.

In Flanders, small storage basins are also often constructed while implementing a landdevelopment or land consolidation project. The construction can be subsidised, and landwill be purchased through ‘expropriation for the public welfare’.

8.4.4 Conclusions on the Flemish legal framework

While studying the applicability matrix for the Flemish Region, the reader will remark thatall inventoried measures can be implemented somehow or other within the current legalframework. However, he will also remark that most of the instruments are not directlymeant to implement measures aiming at water retention or flash floods reduction. Theyare at first designed for other purposes, such as erosion combating or development of‘nature values’. Limiting of runoff will be a secondary result of implementing measuresintended at these goals. The instruments therefore still need some elaboration andreorientation in order to be applicable for water retention purposes.

The appeal of some potentially interesting measures is limited by the fact that they haveno general applicability (for instance measures of which the implementation is limited tonature reserves, or limited to the context of land consolidation projects). The generalapplicability is also important in the context of avoiding certain interventions. Forinstance there is no licence or authorisation required for harmful interventions such asdrainage, ploughing up pastureland, grubbing up hedgerows, paving tracks etc. if theseinterventions do not take place in areas specifically classified by the FlemishGovernment (such as moors, nature reserves, areas of valuable landscape…). Thespatial focus of a number of existing regulations should be reconsidered.

The Flemish instruments concerning land consolidation, land development and naturedevelopment appear to be most powerful regarding the implementation of waterretention enhancing measures. Of course, such projects are implemented over amoderate long to long time frame and often still rely on the goodwill of the actors andstakeholders involved.

Information and sensitisation on the flooding problem, its possible causes and possibleenvironmentally sound solutions to prevent or reduce the risk of flooding are ofparamount importance. Land users must be aware of the impact of interventions in the(upstream parts of the) catchment on the water system in the downstream parts.Sustainable and environmentally sound agricultural practices should be promotedamong the farmers; flood-prone areas should be safeguarded against infrastructure bymeans of a sound land use planning. Effectively using the possibility for includingcompulsory directives in the Flemish land use planning could contribute to this aim.


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Unfortunately, these directives or orders are often omitted because of their (politically)delicate character (for instance the power of the Agricultural Union regardingexpropriations, or the attitude of land users towards the ban on certain cultivationmethods). This once more shows the importance of a thorough sensitisation andawareness-raising campaign.

The water management policy of the Province of Limburg is directed towards floodingprevention and restricting or reducing the accelerated surface water runoff. They show apreference for storage reservoirs, floodplains and sediment traps, which can beimplemented within the current legal framework as shown in the preceding chapter.

Finally, the Gulp region itself does not experience severe flash floods problems.According to the town clerk of the city of Voeren, the water quality of the Gulp river is amore compelling problem than the water quantity (heavy metal pollution due to formermining activity in the Geul catchment). Therefore nothing structural is being done atpresent to prevent downstream flooding. Before acting on the discharge, qualitativemeasurements will be executed first (e.g. the construction of two sewage treatmentplants is planned in the region). Problems following flash flood events, problemsconcerning water quality and the ecological protection of the river are recently integratedwithin the ‘integrated water management’ policy of the Flemish Government. The watersystems in the Flemish Region have high expectations for the implementation of thisnew instrument!

The decree regarding integral water-resources management, its implementation andexecution, cause an important change in the Flemish Region. The environmental policy(nature and water conservation), the policy concerning land use planning, the socio-economical policy and the agricultural policy are being integrated. The competenceshowever remain fragmented, which is not quite beneficial for the global perception.Integral water-resources management causes the water system being managed tocomply all of its functions. Support of this integral water-resources management by theland use planning policy includes the need for valleys to remain free from being built-onso that natural flooding remains possible and potential conflicts between housing andwater are prevented. The perception of both land use planners and water managers isjoined by drawing up integral river basin-management plans (‘EHNNHQEHKHHUVSODQQHQ’)(operational plans at the level of the river catchment basin, strategic plans at a higherlevel), whereas the planning is carried out at the level of the environmental policy.

8.4.5 Recommendations – Flemish Region

Besides the recommendations already formulated among the conclusions of part 8.4.4,two major general remarks can be added:

- the water system should be considered and accepted as one of the guidingprinciples in the land use planning policy;


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- land consolidation projects and land development projects should be considered asregulating and stimulating instruments regarding the planning of the agrarianinfrastructure.

By introducing the decree concerning integral water-resources management and thebekkenbeheersplannen, the Flemish Government has made a first step towards asustainable catchment management in Flanders. Many of its aspects however still relyon the goodwill and sensitisation of the stakeholders. Therefore it is absolutely requiredto spend enough attention on the supply of information and sensitisation. Theimplementation of the integral water management still needs to be better legallyfounded. The competences remain fragmented among several administrations, which isnot quite beneficial for a global and integral perception.

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8.5.1 Actors in the Walloon institutional legal framework

8.5.1.1 Regional level

As is the case in the Flemish region, all administrative services of the Walloon region areconcentrated in one ministry, the Ministry of the Walloon Region. This ministry countsnine General Directions. Each general direction is divided in Divisions; the Divisions inDirections.

Three General Directions are important in the framework of the present study: theGeneral Direction of Natural Resources and Environment ('LUHFWLRQ� *pQpUDOH� GHV5HVVRXUFHV�1DWXUHOOHV�HW�GH�O¶(QYLURQQHPHQW or DGRNE), the General Direction of townand country planning, housing and national heritage (DGATLP), and the GeneralDirection of Agriculture (DGA). One notes that the competences regarding environment,land use planning and agriculture are spread over three different General Directions24.

Several consulting bodies exist at regional level. For instance, the ‘&RPPLVVLRQ5pJLRQDOH� G¶$PpQDJHPHQW� GX� 7HUULWRLUH’ or CRAT (Regional commission for land useplanning) is a multisectoral consulting body which advises the Walloon government onmatters pertaining to land use planning. Other consulting bodies cover the fields offorestry (&RQVHLO� 6XSpULHXU� ZDOORQ� GH� OD� IRUrW� HW� GH� OD� )LOLqUH�ERLV) and natureconservation (&RQVHLO�VXSpULHXU�ZDOORQ�GH�OD�FRQVHUYDWLRQ�GH�OD�QDWXUH).


The provinces are mainly decentralized institutions of both the federal and the regionalgovernment and are as such entrusted with a number of administrative tasks. The permit 24 At the political level, however, there is more integration: land use and environmental policies are theresponsibilities of one Minister (OH�0LQLVWUH� GH� OD� 5pJLRQ�:DOORQQH� SRXU� O¶(DX�� O¶(QYLURQQHPHQW� HW� OD� 9LHUXUDOH).


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granting powers of the provinces are more restricted in the Walloon region than in theFlemish region. For instance, the provinces in the Walloon region have no role in landuse permit granting (SHUPLV�G¶XUEDQLVPH and SHUPLV�GH�ORWLU), the main responsibility forthese aspects resting with the municipalities.

As explained in more detail in the section on the Flemish region, the provinces canhowever wield some autonomous legislative power.

The Walloon province involved in the Geul project is the Province de Liège.

8.5.1.3 Local level

The municipalities have important tasks in land use planning at local level. Theyelaborate a 6FKpPD� GH� 6WUXFWXUH� &RPPXQDO (Municipal Structure Scheme) and candefine generally applicable rules and restrictions for land use, precising or altering theRegional Land Use Plans, by means of the 3ODQV� &RPPXQDX[� G¶$PpQDJHPHQW(Municipal Land Use Plans).

A consultative body at municipality level (‘&RPPLVVLRQ� &RQVXOWDWLYH� &RPPXQDOHG¶$PpQDJHPHQW�GX�WHUULWRLUH (CCAT)’ or Municipal Consulting Commission on Land UsePlanning advises the municipal authorities on matters pertaining to the elaboration ofMunicipal Land Use plans or Municipal structure schemes. This Commission iscomposed of members of the public who have introduced their candidacy to be memberof such a commission.

Since 1995, the municipalities also have the authority to define additional protectivemeasures in the field of nature conservation, providing these measures are in line with,and more severe than, regional nature conservation legislation. Moreover, municipalitiesare encouraged (by subsidies, among others) to define their own Municipal NatureDevelopment Plan (3ODQ�&RPPXQDO�GH�'pYHORSSHPHQW�GH�OD�1DWXUH or PCDN).

The local population can, to a certain extent, influence the decisions as to proposedmajor infrastructure works via the requirement for public consultation within theframework of environmental and “urbanistic” (formerly “building”) permitting and morespecifically in the context of Environmental Impact Assessments (EIA’s) for suchprojects.

At the local level, of course, one also finds the major stakeholders concerned with floodand erosion control projects: on one hand, the people at the UHFHLYLQJ end of flood anderosion problems (landlords and farmers having property in flood-prone areas, residingtourists...); on the other hand the people whose land use practices can LQIOXHQFH to alarge extent the downstream problems, but who are, themselves, not necessarilyaffected by them.

For both categories, it holds true that existing negative land use practices and habits(e.g. building in flood-prone areas) are often enhanced or maintained by an absence ofpertinent legislation (e.g. insufficient legal protection of wetlands) or an insufficientenforcement of the legislation, where it exists.


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8.5.2 Instruments

8.5.2.1 Water-resources management

As in the Flemish Region, the basic law of 196725 still mainly settles the management ofthe unnavigable watercourses in the Walloon Region. Our Walloon informantemphasized the focus of this law on maintaining, modifying and adjusting the SHUPDQHQWriverbed. He also emphasized that applying this basic law to the letter, should meanestablishing a better runoff or flow in the river system26; or quite contradictory to theupset of this Geul project. The basic law of 1967 has been complemented with a RoyalDecree (‘$UUrWp� UR\DO� SRUWDQW� UqJOHPHQW� GH� SROLFH� GHV� FRXUV� G¶HDX� QRQ� QDYLJDEOHV’,05.08.1970) and with provincial regulations (5qJOHPHQW� SURYLQFLDO� VXU� OHV� FRXUV� G¶HDXQRQ�QDYLJDEOHV, drawn up by the &RQVHLO�SURYLQFLDO).

Unnavigable watercourses of first category are managed by the ‘'LUHFWLRQ� GHV� &RXUVG¶(DX�QRQ�QDYLJDEOHV’ of the ‘'LYLVLRQ�GH�O¶(DX’ (DGRNE), unnavigable watercourses ofsecond category by the Permanent Deputation of the Province and unnavigablewatercourses of third category by the Municipal Council of the involved communities(under supervision of the Province). Landowners must take care of non-classifiedunnavigable watercourses in case the watercourse flows on, or along, their territory.Modifications and improvements on unnavigable watercourses of second and thirdcategory have to be advised and approved by the provincial authorities (the PermanentDeputation). A municipality must realize extraordinary works on unnavigablewatercourses of third category according to the respective provincial regulations. TheProvince does not provide subsidies. The Ministry of the Walloon region may grantsubsidies for ‘improvements’ on the watercourse (neither ordinary maintenance works(e.g. dredging), nor modifications will be subsidised). One can consult the categoricalsubdivision of the unnavigable watercourses in the ‘$WODV� GHV� FRXUV� G¶HDX� QRQQDYLJDEOHV’ at the ‘6HUYLFH�WHFKQLTXH�GH�OD�3URYLQFH’ (A.R. du 30.09.1969). The Walloonpart of the Geul river is classified as an unnavigable watercourse of second category,hence being managed by the Province of Liège.

The Walloon Region currently promotes the construction of storage reservoirs andspillways, which are considered as extraordinary improvements on the watercourse. Aspillway must be planned in the 3ODQ�&RPPXQDO�*pQpUDO� G¶(JRXWWDJH (see below), isowned by the municipality and its dimensions depend on the actual sewerage system. Astorage reservoir will be dimensioned based on the results of a hydraulic study (forinstance as provided for in this current Geul project). The Walloon government maygrant subsidies to municipalities and provinces in case they need to expropriate and buyup a privately owned parcel of land for the construction of such a storage reservoir.However, due to the stringent soil legislation in the Walloon Region, there are problems

25 ‘/RL�GX��UHODWLYH�DX[�FRXUV�G¶HDX�QRQ�QDYLJDEOHV��PRGLILpH�SDU�OD�ORL�GX��MXLOOHW��UHODWLYHDX�UHPHPEUHPHQW�OpJDO�GHV�ELHQ�UXUDX[��0%��HW�SDU�OD�ORL�GX��IpYULHU��0%��’26The law of 1967 was specifically directed towards drainage to improve agricultural practice alongunnavigable watercourses (or contrary to the environment-friendly target!).


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concerning the dredging of the storage basins. The same soil legislation is responsiblefor the low presence of sediment traps in the Walloon Region. This, of course, doescount especially for the policy regarding erosion reduction, and does not count for muchregarding increased water retention. Sediment traps in the upstream catchment,however, do help avoiding severe mudflows in the urban area during high rainfall events.

The decree of 1970 declares, among other things, a ban on cultivating, building andpasturing the 0.5 m border along a watercourse. The Walloon government updated thedecree in 1985 (‘$UUrWp�GH� O¶H[pFXWLI�5pJLRQDO�:DOORQ�PRGLILDQW� O¶DUUrWp�UR\DO�GX��DR�W�� SRUWDQW� UqJOHPHQW� JpQpUDOH� GH� SROLFH� GHV� FRXUV� G¶HDX� QRQ� QDYLJDEOHV’,30.01.1985).

Building on the land along an unnavigable watercourse is not forbidden in the WalloonRegion, provided that a construction licence is granted. Building on floodplains, or flood-prone areas, however will not be allowed. In general, if the $GPLQLVWUDWLRQ�&RPPXQDOH orthe 'LUHFWLRQ� SURYLQFLDO� GH� O¶XUEDQLVPH need to decide on granting a licence (forconstruction or reallotment…) concerning a domain along a watercourse, they have toconsult the 6HUYLFH� H[WpULHXU of the 'LUHFWLRQ� GHV� FRXUV� G¶HDX� QRQ� QDYLJDEOHV or the6HUYLFH� WHFKQLTXH� SURYLQFLDO (for watercourses of first/second or third categoryrespectively). They will be given an unfavourable advice if the considered domain issituated in a flood-prone area (either defined or not by the 'LYLVLRQ�GH�O¶(DX).

The land along a watercourse could alternatively be protected from building by means ofthe ‘ORL�VXU�OHV�GLJXHV’ (18/06/1979), which concerns among other things the protection ofthe hinterland.

The provincial regulations must be approved by the Walloon government and arepublished in the 0pPRULDO�$GPLQLVWUDWLI. Among other things, the 5qJOHPHQW�SURYLQFLDOidentifies the rules regarding ordinary maintenance works (what to do, terms…), imposesa yearly control visit to all classified unnavigable watercourses (by the $GPLQLVWUDWLRQV&RPPXQDOHV and the 6HUYLFH� 7HFKQLTXH� 3URYLQFLDO), explains the procedures forobtaining a licence to perform modifications and improvements (extraordinary works) onunnavigable watercourses (for instance a licence is needed for constructing a storagebasin), and declares some police rules (imposed minimum distance between thewatercourse and plantations along this watercourse, prohibition on planting trees alongthe watercourse without being authorized by the Municipal Council…). Violation of this5qJOHPHQW�SURYLQFLDO will be penalized.

An extract out of the Règlement provincial of the Province of Liège is given below:

“Article 38: il est défendu de construire des murs ou des bâtiments, de planter des arbres en bordure descours d’eau sans autorisaton préalable du Conseil communal, qui fixe l’alignement sur avis de l’Ingénieur enchef-Directeur du Service Technique Provincial, sauf recours à la Députation permanente. Pour lesplantations, cet alignement est fixé à 3 m de la crête de la berge du cours d’eau. Cette distance est portée à6 m dans le cas d’une plantation résineux.”

Special regulations exist as regards the distance between unnavigable watercoursesand touristic infrastructure (e.g. camping sites, caravan parks, holiday centres…). For


Legal Framework 137

instance, a ‘free border’ (no infrastructure) of 8 m must be maintained between acamping site (FDPSLQJ�FDUDYDQLQJ) and a watercourse (measured from the riverbank orfrom the averaged high water mark). The infrastructure-free border can even beincreased up to 15 m or more. Touristic infrastructure may on no account be located inflood-prone areas. ('pFUHW�GX�&RQVHLO�GH�OD�&RPPXQDXWp�IUDQoDLVH�GX��UHODWLIDX[�FRQGLWLRQV�G¶H[SORLWDWLRQ�GHV�WHUUDLQV�GH�FDPSLQJ�FDUDYDQLQJ.)

In the near future, all Walloon municipalities are obliged to have a municipal drainageplan, or, ‘3ODQ�&RPPXQDO�*pQpUDO�G¶(JRXWWDJH’. A drainage plan indicates the areas inthe community having collective water treatment, the areas having individual watertreatment and the involved infrastructure (sewage treatment plants, spillways, retentionreservoirs, dispersion drain pipes…). After the PCGE being approved, the MunicipalCouncil must draw up municipal sewerage regulations and an implementationprogramme for the PCGE. Every other year, the municipality has to report to the0LQLVWqUH� GH� O¶(QYLURQQHPHQW�� GHV� 5HVVRXUFHV� QDWXUHOOHV� HW� GH� O¶$JULFXOWXUH. TheWalloon government can provide subsidies ($UUrWp�GX�*RXYHUQHPHQW�ZDOORQ�UHODWLI�j� ODVXEVLGLDWLRQ�GHV�SODQV�FRPPXQDX[�JpQpUDX[�G¶pJRXWWDJH, 23.06.1994). The PCGE andthe municipal sewerage regulations are included in the present inventory because oftheir sensitisation and awareness-raising opportunities.

Since 1993, the Walloon Region can enter into so-called ‘river contracts’ (&RQWUDW� GH5LYLqUH)27. A municipality should apply for it. A river contract is an agreement between allpublic and private actors in a catchment basin (representatives of sewage treatmentplants, of the agricultural sector, of the municipalities, the Province, natureorganisations…); aimed at reconciling the different functions of a river, of the riverbanksand of the water stored in the considered basin. Currently, there are eight standingcontracts; there is no &RQWUDW�GH�ULYLqUH for the Geul river yet.

Each contract should reflect two main principles:

1. aiming at an integral, or complete, approach of the watercourse;

2. participation of, and cooperation with, all actors involved.

Entering into a river contract comprises, except for consensus forming between politics,social life, economy, science and others, several goals that could be of relevance in thecurrent Geul project, for instance:

• integrating the ‘water’ dimension in the policy concerning land use planning,agriculture, industry, tourism, environment…;

• affecting the behaviour and attitude of water users and managers:

A river contract requires sensitisation, information and cooperation of all actors in thecontract area, in order to establish a sustainable and integral water-resourcesmanagement. A ‘follow-up’ committee must observe the implementation of each

27 &LUFXODLUH�PLQLVWpULHOOH�UHODWLYH�DX[�FRQGLWLRQV�G¶DFFHSWDELOLWp�HW�DX[�PRGDOLWpV�G¶pODERUDWLRQ�GHV�FRQWUDWVGH�ULYLqUH�HQ�5pJLRQ�ZDOORQQH��PRGLILpH�SDU�OD�FLUFXODLUH�GX��MXLQ��HW�GX��MXLQ��, 18.03.1993


Legal Framework 138

contract. Municipalities, provinces and the Walloon Region can subsidise the necessaryworks as proposed for in the river contract. The regional subsidy is granted for theduration of the agreement, but however restricted to the total amount of money allocatedby the municipalities and provinces.

The project area neither belongs to a ‘3ROGHU’ nor a ‘:DWHULQJXH’.

8.5.2.2 Land use planning

The existing body of legislation on land use planning in the Walloon region is containedin the &RGH�:DOORQ�GH� O¶$PpQDJHPHQW� GX�7HUULWRLUH�� GH� O¶8UEDQLVPH� HW� GX�3DWULPRLQH(CWATUP) or Code of land use planning, town planning and national heritage.

This code contains several basic decrees and their application texts, the latter being thetools that should translate the decrees into measures and allow for the realisation of theregional policy objectives.

Several tools can and are being used in the framework of attaining the overall objectiveof the Code, being “to satisfy in a sustainable way the social, economic, environmentaland patrimonial needs of the collectivity”.

Planning tools:

The outlines of the Walloon land use planning policy are defined in the 6FKpPD� GH'pYHORSSHPHQW� GH� O¶(VSDFH� 5pJLRQDO or SDER (Regional Territorial DevelopmentScheme). This is an indicative planning tool that, among many other things, defines theconceptual framework for the Regional Land Use Plans (SODQV� GH� VHFWHXU) and themunicipal land use plans (3ODQV�&RPPXQDX[�G¶$PpQDJHPHQW).

At municipal level, the ‘6FKpPDV�GH�6WUXFWXUH�&RPPXQDO’ (SSC) have a similar role asthe SDER, forming the inspiration for the municipal land use plans. A municipality ishowever not obliged to elaborate a SSC.

Neither the SDER nor the SSC have a legislative value.

Legislative tools that define and fix the land use:

1. Land use plans

More pertinent land use rules and restrictions are defined in the land use plans (SODQV�GHVHFWHXU).

Land use plans are spatial planning instruments. They allow defining rules andrestrictions for land use on set and clearly defined areas. An environmental impactassessment ((WXGH� G¶LQFLGHQFHV� VXU� O¶HQYLURQQHPHQW or EIE) is often required forchanges to existing land use plans.


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The decree of 27/11/1997 has introduced into the Walloon legislation the divisionbetween areas scheduled for urbanisation28 and areas for which this is not the case. Thelatter include agricultural areas, forest areas, green areas, parks and nature reserves.The functional definitions of these areas can include uses complimentary with the mainfunction: for instance agricultural areas are formally defined as having a role to play inthe creation and the preservation of the landscape. Likewise, forestry areas have asadditional function to preserve the landscape and the ecological equilibrium.

Apart from the main divisions, additional zones with specific characteristics can bedelineated on the Land Use Plans. This is the case, among others, for areas wherenatural risks can be expected. One of the areas that satisfy this definition are the flood-prone areas in river valleys. The CWATUP specifically prohibits transforming (via therevision of land use plans) areas not intended for urbanisation into areas whereurbanisation is a possibility, whenever these areas are catalogued as areas wherenatural risks can be expected.

2. Site protection

Site protection (‘FODVVHPHQW�GHV�VLWHV’) is a tool used in land use planning to preservecharacteristic and homogeneous areas and landscapes. This label allows for theprotection of hedgerows, forests and wetlands within the limits of the classified sites.

3. 3ODQV�FRPPXQDX[�G¶DPpQDJHPHQW (PCA)

These are local tools that allow to better define, adapt or even change (under certainrestrictions) the land use as defined by the (regional) land use plans.

4. 3HUPLV�G¶XUEDQLVPH�(land use permits)

Formerly called building permits, these permits cover a larger field. For instance, thefollowing activities are also covered by the land use permitting system:

• afforestation of an agricultural area

• deforestation of an area

• changes to the topography of an area (note that this definition can and is beingapplied to works entailing the modification of riverbeds or banks, as well as to theconstruction of even minor ponds, basins, dikes, levees...)

• cutting of individual trees in green areas

• cutting of remarkable trees or hedgerows, in so far as they figure on a list definedby the Government.

• changing the vegetation of moors and heaths

28 In the large sense of all uses not related to agriculture, forestry and nature conservation; quarrying, forinstance, is considered a form of urbanization.


Legal Framework 140

Land use or allotment permits (SHUPLV�GH� ORWLU) are subject to a number of regulations,both at the regional and the municipal level. These regulations intend to ensure that theconstructions satisfy certain conditions regarding quality, aesthetic value, accessibilityand so on. Security is also a factor: land use permits are excluded or subjected to anumber of restrictions in areas where a major natural risk exists, such as flood-proneareas.

Holiday villages have to comply to a specific set of rules, among which the requirement,along a watercourse, to leave free of any construction a border of 20 meter wide fromthe average high water mark, and the requirement to ensure total surface water drainageof the area.

Additionally, the construction of residential weekend parks is specifically forbidden inflood-prone areas.

8.5.2.3 Agricultural policy

Agriculture and agricultural policy is mainly a federal competence in Belgium.Nevertheless, the regions do have some powers in this field. Within the framework of thepresent study, two aspects are worth mentioning:

1. Agro-environmental subsidies

This item is covered by a recent decision of the Walloon government (March 11, 1999).This decision defines a list of eleven agricultural practices that are considered anessential part of a sustainable and environment-friendly farming approach and as sucheligible for subsidies.

The following practices are of relevance within the framework of the current study:

• Creation of grassed strips and turnaround strips:

- Creation of low-input grassed strips, 4 to 20 meters wide, along the field edges;

- Creation of cropped strips, 4 to 20 meters wide, along field borders, subjected toa low-input cultivation method, in contrast to the method applied to the remainderof the field;

- Creation of grassland strips, 8 to 20 meters wide along water courses andorchards;

• Conservation and maintenance of small landscape and biodiversity elements suchas hedgerows, tree lines, wooded strips and ponds;

• Seeding of a soil cover crop between two main growing seasons such as to maintaina soil cover as permanent as possible;

• Low-input management of humid grasslands, excluding drainage.


Legal Framework 141

2. Land consolidation projects

Land consolidation projects are intended to minimise agricultural production costs inrural areas, by optimising land allotment patterns and carrying out necessaryinfrastructure works (rural roads, drainage works…). At the same time, these projectsoffer the opportunity to enhance the ecological quality of the rural landscape and tomaximise the soil and water conservation functions of certain ecosystems.

Since 1977, the land consolidation legislation imposes the drafting of a land evaluationplan (3ODQ� G¶pYDOXDWLRQ� GHV� VLWHV) prior to any land consolidation project. This planconsists of an inventory and a valuation of all natural riches in the area. This inventorycan serve as a reference and as the basis for assessing the suitability of any proposedintervention, from an environmental-conservationist point of view. The drafting of thisplan is subsidised for the full 100% by the Walloon Region.

In a next step land organization plans (3ODQV�G¶DPpQDJHPHQW�GHV�VLWHV) can be drafted,though this is not compulsory under the current legislation. These plans define the limitsimposed on specific activities within the framework of land consolidation projects in thearea, with the intent of protecting or enhancing its natural values. They define the “do’sand don’ts” and serve as a general guide and an environmental framework for the landconsolidation project. Land consolidation committees receive an 80% subsidy from theWalloon Region towards the costs of drafting the plan.

The result of this integrated approach has been that in recent years, much more thanbefore, land consolidation projects have taken the opportunity of maintaining or evenenhancing valuable natural elements that play an important role in soil and waterconservation, such as ponds, wetlands, and hedgerows. Moreover, infrastructure workslike rural roads can and are being designed in such a way as to control runoff, whileothers are being constructed specifically with this purpose in mind (flood control basins,artificial wetlands…). This renewed approach to land consolidation, while still focused onimproving conditions for agriculture, nevertheless has come to recognise the role ofnatural landscape elements in soil and water management and thus their contribution toa sustainable agriculture.

8.5.2.4 Environmental Policy

1. Pertaining to water resources management

Water resources management in the Walloon Region has been dealt with earlier in thisChapter.

Note that certain types of works such as drainage works or riverbed regulation can, inaccordance with European law, be subjected to an environmental impact assessment.An EIA is required in any case for the creation of an impoundment if the water areaexceeds 1 ha in sensible areas (10 ha in other areas).


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There is no specific and integrated legal tool that protects valley bottom wetlands as awhole, although texts conferring partial protection can be found in a number oflegislations. Examples are:

• the provisions in the land use planning legislation, concerned mainly with theprotection of assets in flood-prone areas as well as the restrictions concerningtouristic constructions along river banks (see above);

• the interdiction to plant resinous trees (specifically fir trees) less than six meters froma river bank;

• the interdiction to drive motorized vehicles on riverbanks,...

2. Pertaining to protection and management of forest resources and ecosystems

The main legal basis for forest management in the Walloon region is the &RGH�)RUHVWLHUof 1854, amended and updated a great number of times since. The power of this code,which deals mainly with the economic aspects of forest management, does only partiallyextend to privately owned forests.

All forests though are subject to clear restrictions as regards cutting, land clearing andextraction of litter, humus or other soil components.

Special management directives (imposing, among others, limitations to clearing and landdrainage) have been developed for selected zones such as impoundment watersheds,valley bottoms and source areas.

The code specifies a number of cases for which subsidies can be requested. It concernsactivities aiming at:

• the improvement of the forest patrimony, which includes subsidies for theafforestation of agricultural lands;

• the opening of forests to tourism and recreation;

• forest protection and restoration;

• awareness-raising of the public to the economical, social, ecological and protectingfunction of a forest.

Forest improvement requiring drainage works is not eligible for subsidising, as thispractice is considered contrary to the policy that forests should contribute to regulation ofthe water cycle.

Note that the Walloon region subsidises the planting of hedgerows composed ofindigenous species, on condition that the recipient of the subsidy accepts to maintain thehedgerows during a 20-year period29.

29 Arrêté du Gouvernement wallon relatif à l’octroi d’une subvention pour la plantation de haies du 9 février1995


Legal Framework 143

In privately owned forests, the 6HUYLFH�GHV�(DX[�HW�)RUrWV can, on the basis of a speciallaw (law of 28 December 1931) forbid massive clearing if the forest has a clear functionin soil stabilisation on steep slopes.

Remember that any forest clearing (if not followed by replanting of trees) requires a‘SHUPLV�G¶XUEDQLVPH’ within the framework of the land use legislation and that the sameholds for planting of trees outside forest areas. Afforestation of non-forest areas can alsobe subjected to the requirement of an EIA under the relevant legislation, if negativeecological impacts are suspected.

The ecological value of forests is recognised through the Nature Conservation Law (/RLVXU�OD�FRQVHUYDWLRQ�GH�OD�1DWXUH�(1973) and its many modifications) that has introducedthe notion of forest reserves and nature reserves.

Theoretically, this law allows for the expropriation of privately owned lands if such is inthe interest of nature conservation (Art.6, par.4). On the other hand, privateorganisations can be subsidised for the acquisition of land intended for the creation ofnature reserves. In nature reserves, it is forbidden, among many other things, to dig,quarry, change the natural soil level and influence the ground water and surface waterregime. Restrictions for forest reserves are less stringent.

Article 37 of the law allows measures to be taken (including subsidies) in the interest ofnature conservation, that favour the protection of vegetation on steep slopes and theprotection of vegetation along rivers.

Article 58 states that it is forbidden to install drainage ditches in areas defined as naturezones, or nature reserves by the regional Land Use Plans.

Special protection is conferred to wetlands (]RQHV�KXPLGHV) since 1989 ($UUrWp�UHODWLI�jOD� SURWHFWLRQ� GHV� ]RQHV� KXPLGHV� G¶LQWpUrW� ELRORJLTXH), in as far as the ecological andscientific value of a particular wetland is officially recognised. While this text recognisesthe basic role that wetlands have to play in regulating the hydrological cycle, it is mainlyconcerned with conservation of species of fauna and flora within wetlands, not withhabitat preservation as such.

Other protected areas, in line with European Union legislation, are the Special ProtectionZones and Special Conservation Zones or “Habitat” areas.


The applicability matrix (Table 8.6) compares the instruments as mentioned in part 8.5.2against several potential flash floods reducing measures (potentially applicable technicalmeasures, simulated in Chapters 6 and 7). The matrix gives an idea about the relevanceand the applicability of each instrument with respect to water retention purposes.

A distinction was made between instruments which are: (�) applicable (already enforced– symbol used in the applicability matrix is ‘�’), (�) possibly applicable (needs furtherinvestigation and elaboration – symbol used in the matrix is ‘�’), (�) not applicable (cannot be used in this framework – QR� V\PERO in the applicability matrix) and (�)


Legal Framework 144

instruments which are not meant for water retention purposes at first, but which couldhave an indirect positive effect on flash floods reduction while being used for anotherpurpose (symbol in the matrix is ‘L’). The matrix in Table 8.6 also indicates the time frameover which instruments could be used to implement a measure; a distinction was madebetween short term (0-5 years), middle long term (5-10 years) and long term (10-15years). The availability of financial resources and whether usage of the instruments isbased on a voluntary basis are also indicated.

Table 8.6 Applicability matrix for the Walloon legal framework

0HDVXUHV��,QVWUXPHQWV

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unal

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Con

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re

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ans

Site

pro

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Mun

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al la

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se p

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Land

use

per

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Law

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natu

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rvat

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Policy of sensitisation and awareness-raising 0 0 + i 0 0 i i

Incentives policy + 0 + i i i

Adjustment of riverbed 0 0

(Re-) allocation of the riverbed 0 0

Creation of wetlands 0 0 0 i i i i 0 i 0

Ground cover and limited fallow 0 + 0 0

Turn high sloping areas to grassland/wood 0 i i i i + +

Re-introduction of hedgerows/green belts 0 i + 0

Principles of sustainable farming 0 +

Land retirement 0 i 0 0

Adjustment of parcelling i

Storage basin (river/upstream) 0 0 0

3HULRG (l=long; s=short; m=middle long term) s s m l m m s s m l m

)LQDQFLDO�UHVRXUFHV (y=yes; n=no) y y y y y y y y y y y

9ROXQWDU\ (y=yes; n=no) y y y/n n n n n y n n y

30 At this point, the term ‘water-resources management’ covers the basic law of 1967 concerning theunnavigable watercourses, the decree of 1970, the ‘loi sur les digues’. and the provincial regulations


Legal Framework 145

As can be seen from the above table, the potential flash flood reducing measuresselected in the present study are to a greater or lesser extent supported or enhanced bythe existing legal framework:

Sensitisation and awareness-raising to the need for water retention in the watershed canmost effectively be implemented within the framework of interventions that clearlycontribute to reaching this goal. For instance, DJUR�HQYLURQPHQWDO�VXEVLGLHV don’t alwayshave water retention objectives as their primary goal, and this is even less the case forODQG�FRQVROLGDWLRQ�SURMHFWV. Nevertheless, there is room for implementing measures thatcontribute to water retention within the framework of the said legal instruments, whichmakes them a good vehicle for awareness-raising. This is especially true for landconsolidation projects, which are preceded by thorough preparation phases in whichthere is plenty of interaction between official instances and the farming community.

Awareness-raising can also be done within the framework of the )RUHVW� 'HFUHH; itspecifically allows for the subsidizing of activities aimed at “awareness-raising of thepublic to the (…) ecological and protective function of the forest”. It seems logical thatthe role of forests in the hydrological cycle should also be treated under these activities.The VLWH�SURWHFWLRQ� OHJLVODWLRQ and the ODZ�RQ�QDWXUH�FRQVHUYDWLRQ (and more preciselythe possibility to confer protection to certain wetlands) can also indirectly be vehicles forawareness-raising, by stressing the importance of regulation of the water cycle (next toecological and esthetical values) as a secondary criterion in the decision to protect a siteor a wetland.

Sensitisation and awareness-raising towards enhanced water retention in the catchmentbasin could be implemented within the current ZDWHU�PDQDJHPHQW�SROLF\. The WalloonGovernment and the Province, for instance, do promote the construction of waterstorage reservoirs (‘extraordinary improvements on the watercourse’); the PCGE maycontain special regulations that point at increased infiltration or at the construction ofdispersion drain pipes instead of ordinary drain pipes. Building on the watercourseborders is not advisable (e.g. distance regulations, ORL� VXU� OHV� GLJXHV). The mentionedinstruments however, still need some modifications or supplementations GLUHFWO\ orspecifically focusing on the need of enhanced water retention in (the upstream parts of)the catchment. A river contract may contribute considerably to enhanced sensitisation,being a prerequisite in handling the problem. All stakeholders and actors are involved,and the contract directly aims at affecting the behaviour of policy-makers and land- andwater users in the region in order to perform ‘integral water management’.

Financial incentives to implementing water retention measures in the watershed can befound in a number of legislations and regulations. For instance, in subsidising theconstruction of storage reservoirs (ZDWHU�UHVRXUFHV�SROLF\). However, water retention isoften only a secondary purpose or an indirect outcome of measures implemented in thepursuit of other objectives. The DJUR�HQYLURQPHQWDO� VXEVLGLHV are a clear example:creation of grassed strips, seeding of a soil cover (both essentially anti-erosionmeasures), conservation of hedgerows, wooded strips and ponds (intended mainly tomaintain biodiversity) as well as the conservation of humid grasslands all can contribute


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to less, or to more evenly distributed, runoff; and all of these measures are eligible forsubsidies.

The IRUHVW�GHFUHH allows for the subsidising of activities aimed at “the improvement ofthe forest patrimony”, which also covers the afforestation of agricultural lands and thusthe extension of forested area in a given watershed.

Finally, the ODZ� RQ� QDWXUH� FRQVHUYDWLRQ makes it possible to subsidize privateorganisations for the acquisition of land intended for the creation of nature reserves. Thismeasure can indirectly contribute to a better water retention in the watershed as a wholeif one assumes that areas subjected to “natural” management have better waterretention capacities than agricultural areas.

If the extraordinary modifications and improvements on unnavigable watercourses (inthe EDVLF� ODZ�RI� ��) are interpreted to improve the water flow within the context of‘integral water management at catchment level’, adjustments of the riverbed will beperformed to slow down the water flow. For instance, constriction devices could beinstalled to locally obstruct the river water flow. Of course, this requires a storagereservoir (e.g. retention basin, floodplain, wetlands). As a river contract aims atreconciling the functions of the river, the riverbank and the water stored in the rivercatchment basin, adjustments of the riverbed to enhance water retention could beproposed to fulfil this aim.

The EDVLF�ODZ�RI�� focuses on riverbank protection and therefore often prevents therepositioning of the actual course – the bed – of the river. The &RGH�&LYLO, on the otherhand, points at ‘ODLVVH]� IDLUH� OD� ULYLqUH’, or thus at freely meandering. According to theland use type of the area a river flows through, the one or the other regulation will beimplemented. For instance, in urban areas a watercourse will often be embanked;whereas in pastureland the watercourse will be allowed to freely meander. Re-allocationof the riverbed, in order to slow down the water flow, can be implemented within thecurrent water-resources policy. It is still of paramount importance that a sound land useplanning is established, and that the ‘water dimension’ is fully integrated or even adirective in this land use planning (cf. the river contracts).

A number of existing legislations or legislative tools are relevant where the creation orconservation of wetlands is concerned. The CWATUP limits the revision of ODQG� XVHSODQV if such revision would result in the (potential) urbanisation of existing flood-proneareas. The power of the municipalities to change, via the PXQLFLSDO�ODQG�XVH�SODQV, theland use as defined by the regional land use plans, could theoretically also affect theconservation of wetlands.

/DQG�XVH�SHUPLWV are subjected to a number of restrictions in flood-prone areas. In thiscontext, it should also be mentioned that changes to the topography of an area require aland use permit; the creation of wetlands that would require the construction of evensmall levees could as such be subjected to the permitting process.


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6LWH�SURWHFWLRQ allows for the protection and thus the conservation of wetlands within thelimits of a classified site. The IRUHVW� GHFUHH also has an indirect impact on thepreservation of natural wetlands, as it limits drainage in selected forested areas (valleybottoms, source areas) and does not subsidise forest improvement activities that requiredrainage.

/DQG� FRQVROLGDWLRQ� SURMHFWV are more directly concerned with the creation of artificialwetlands, if such can be done within the framework of the larger objective to improvewater management in a given area (ZDWHU�UHVRXUFHV� SROLF\). Artificial storage basinsintended to control runoff can and are effectively being implemented in the form ofwetlands.

Finally, the ODZ�RQ�QDWXUH�FRQVHUYDWLRQ prohibits the drainage of nature zones and naturereserves and allows for the protection of wetlands. The latter is only possible if the saidwetland has a recognised ecological and scientific value, which restricts the applicabilityof this measure for the primary objective of water retention in the watershed.

Due to its integrated approach of a water course, the ULYHU� FRQWUDFW appears to be ahighly valuable and favourable tool for proposing all kinds of water retention enhancingmeasures; measures to slow down the water flow (also concerning the policy on landuse planning, the environmental policy: creation of wetlands, cultivation of green belts,planting of hedgerows, providing for ground cover etc.). Of course, the proposedmeasures need to be implemented as well. A follow-up committee has to watch theexecution of the works.

Maintenance of permanent ground cover is most effectively implemented under theprovision for DJUR�HFRORJLFDO�VXEVLGLHV, which makes it possible to subsidize the seedingof a soil cover crop between two main growing seasons as well as the creation orconservation of grassed or wooded strips. Both the IRUHVW�GHFUHH and the ODZ�RQ�QDWXUHFRQVHUYDWLRQ contribute to maintaining or even extending the area under permanent soilcover in a given watershed, by subsidising the afforestation of agricultural land and theacquisition of land for the creation of nature reserves. Note, however that theafforestation of agricultural areas requires in any case a ODQG�XVH�SHUPLW�and in somecases even an HQYLURQPHQWDO�LPSDFW�DVVHVVPHQW�

A number of legal texts have to be taken into consideration when the turning of highsloping areas into grassland or wood is concerned, first among them the IRUHVW�GHFUHHthat can subsidize afforestation schemes (again subject to obtaining a land use permit).The law of 28 December 1931 specifically forbids massive clearing of forests that have aclear function in the stabilisation of steep slopes. The /DZ�RQ�QDWXUH�FRQVHUYDWLRQ allowsfor the protection of forests (and other permanent vegetation forms) on steep slopes asforest or nature reserves if these areas are recognised to have an important naturalvalue. Moreover, the law specifically allows measures to be taken, including the grantingof subsidies, which favour the protection of vegetation on steep slopes. 5HJLRQDO� DQGPXQLFLSDO� ODQG�XVH�SODQV can contribute to the afforestation of steep slopes by settingthese areas aside as nature zones, nature reserves or forestry zones. 6LWH� SURWHFWLRQ


Legal Framework 148

can cover large parts of a given watershed and protect forests within the boundaries ofthe protected sites, on condition that the forests are part of a typical landscape worthprotecting.

Introduction of hedgerows or green belts (or the conservation of said elements) isspecifically covered by the legislation on DJUR�HQYLURQPHQWDO�VXEVLGLHV� which subsidizesthe conservation and maintenance of hedgerows, tree lines and wooded strips. /DQGFRQVROLGDWLRQ�SURMHFWV can contribute to the preservation of hedgerows if the initial landevaluation plan has identified them as a valuable element. Cutting of hedgerows alsorequires a ODQG�XVH�SHUPLW, but only if they are identified as being valuable and as suchfigure on a list compiled by the government.

The principles of sustainable farming are favoured by the system of DJUR�HQYLURQPHQWDOVXEVLGLHV, which form an incentive program accessible to all farmers and not limited tocertain regions or areas.

Land retirement is actively made possible by both the IRUHVW� GHFUHH and the ODZ� RQQDWXUH�FRQVHUYDWLRQ. The former subsidizes the reforestation of agricultural land (subjectto a land use permit); the latter allows for the expropriation of privately owned land in theinterest of nature conservation and subsidizes the acquisition of land intended for thecreation of nature reserves.

Adjustment of parcelling is frequently carried out within the framework of ODQGFRQVROLGDWLRQ�SURMHFWV. Its primary objective is however to optimise working conditions foragriculture, not to maximize water retention in the watershed. It should be ascertainedon a case-by-case basis if both objectives are compatible in a given situation.

Storage basins can be realized (artificial) or identified (wetlands, floodplains) within thecurrent water management policy.

8.5.4 Conclusions on the Walloon legal framework

As shown in the preceding paragraphs, most of the proposed measures fit in theframework of at least one legislative tool and no major contradictions between proposedmeasures and existing legislation have been identified. Crippling contradictions betweenlegislations have not been found either, although many differences in focus can befound, for instance between the forest decree which actively sustains afforestation ofagricultural land by subsidizing it, and the land use and environmental legislation whichlimit its appeal by requiring a land use permit and in some instances even anenvironmental impact assessment.


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As for the Dutch and the Flemish legislative framework, the same general conclusionscan be drawn regarding the Walloon Region. No legislation provides a complete set ofrules to sustain water retention at catchment level; limiting of runoff is usually no primarygoal; and most relevant legislation does not have an area-based perspective. The onlyexceptions to this, almost by definition, are once more the land consolidation projects.

Especially the ODZ� RQ� QDWXUH� FRQVHUYDWLRQ is rather disappointing in this respect. Itspotential as a tool for land and water conservation is severely limited by its focus onspecies and habitat protection. Generally applicable rules for given forms of land use dohardly exist. The appeal of its potentially interesting measures is greatly limited by thefact that they have no general applicability: wetlands can only be protected if theirecological value has been recognised and the limitations the law sets on certainpractices do only apply to areas identified as valuable by either the land use legislationor the nature conservation legislation

The IRUHVW� OHJLVODWLRQ, although traditionally focused on the productive function of aforest, has a more general applicability. Although most of its forest-management relatedregulations do not extend to privately owned-forests, other measures and limitations arevalid for all forests. The ODQG�XVH� OHJLVODWLRQ, although area-based and thus potentiallyappealing, is often not specific enough in its prescription of allowed or restricted uses fora specific land use class or does not link them to hydrological management. It would beadvantageous if criteria related to water management at a basin level (minimising runoff,for instance) could be used to assess the suitability of a given form of land use in a givenarea. Especially the PXQLFLSDO� ODQG� XVH� SODQV seem to have a scale that is perfectlyadapted to contribute to the objective of water retention.

The current legislation and policy regarding ZDWHU�UHVRXUFHV� PDQDJHPHQW could beapplied in the Walloon Region to enhance water retention in the Geul watershed andslow down the river water flow, if the awareness of the need of this is thoroughly foundedamong Walloon policy makers and land users. People must be aware that a soundmanagement of the upstream parts of the Geul catchment could considerably reduce thedamage caused by flash flood events and accompanying mudflows in the downstreamparts. A catchment needs to be managed by means of an integrated approach: a riverbasin does neither stop at the borders of the riverbed, nor at the borders of a country.The Walloon government gave the initial impetus to this awareness-raising byintroducing the ULYHU� FRQWUDFWV. Unfortunately, there are only eight standing rivercontracts at the moment in the Walloon Region and the Geul river is not yet considered.Besides, although the initiative of the river contracts being admirable, the determinationof regulations and the execution of these regulations often still depends on the goodwillof the involved parties. A more stringent legislative framework to support not only the up-set of a river contract, but also its implementation, should be established. Furthermore, ifthe basic law of 1967 were to be interpreted and implemented to the letter,environmentally sound measures wouldn’t make a chance in the Geul catchment andonly the minor riverbed would be considered. Potential revisions of the legislationconcerning unnavigable watercourses should pay particular attention to this point.


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However, it is interesting to note that the legislations that seem to best sustain theproposed measures or at least have the potential to do so are both concerned withagriculture, not with nature or water conservation. /DQG�FRQVROLGDWLRQ�SURMHFWV have anarea approach and a scale that is ideally suited to implement many of the proposedmeasures. Although their primary goal is to optimise working conditions for agriculture,this does not exclude taking measures that favour water retention, and even provide thefinancial and technical means to do so. The system of DJUR�HFRORJLFDO�VXEVLGLHV is alsoan attractive instrument that allows for the implementation of a number of the waterretention measures proposed in the present study. Its effectiveness could be furtherenhanced by providing subsidies for measures specifically aimed at increasing waterretention and by making it possible to differentiate the measures eligible for subsidiesand even the amount of the subsidies on an area basis.

8.5.5 Recommendations for the Walloon region

It has been noted that the existing legal instruments pertaining to water retention in awatershed are few and spread out over a number of sectorial legislations. Takentogether, they do not form a consistent policy or translate into a consistent set ofmeasures. The same holds for the institutional setting, which does not show a global andclearly assigned responsibility for matters pertaining to water management at basin leveleither, but rather a fragmented set of sometimes partially overlapping responsibilities atdifferent levels of different administrations. This should not come as a surprise, sincewater management at basin level is not a separate policy field, contrary to for instanceland use, environment and forestry. This situation, ultimately, reflects the importancesociety adheres to watershed management.

An integrated watershed management policy, although it would effectively allow for thesolution of many of the problems encountered in the Geul catchment, is – howeverintroduced by the river contracts – therefore not likely to be in operation within the nearfuture. With this in mind, efforts should be directed at making possible minor but effectivechanges to the existing legislation, and to better co-ordinate actions betweenresponsible administrations. This general remark translates into the followingrecommendations:

• Responsibility for the co-ordination of the different water management efforts carriedout within the catchment should be assumed by a clearly defined institution, whichpreferably should also have the capacities and the funding to implement measuresby itself. Ideally, this institution should take the form of an independent River BasinAuthority, being able to operate at an interregional or even international level. Withinthe current institutional framework for the Walloon Region, one could imagine thateither a modified “FRQWUDW� GH� ULYLqUH” (with stipulations regarding execution andimplementation) be concluded for the Geul catchment, or that the Province of Liègeassumes the required coordinating responsibility.


Legal Framework 151

• Contributing to the management of the natural surface water cycle in a catchment(e.g. limiting runoff in hilly regions) should become a declared side-objective ofseveral of the existing legislations, the IRUHVW� GHFUHH and the ODZ� RQ� QDWXUHFRQVHUYDWLRQ being the prime examples. Other possible instruments that offeropportunities for integrated watershed management that could restate their goals toinclude these added objectives are VLWH� SURWHFWLRQ, and the practices of DJUR�HQYLURQPHQWDO�VXEVLGLHV and ODQG�FRQVROLGDWLRQ.

• The spatial focus of a number of existing regulations should be reconsidered. Thepower of a number of instruments contained in the law on nature conservation couldbe greatly improved if their field of application would extend beyond officiallyrecognised protected areas. Moreover, it should be considered whether a spatialdifferentiation of existing legislation wouldn’t be advantageous in a number of cases:one could imagine, for instance, that the approach to land consolidation projects,forest management or nature conservation would be regulated to be different inwatersheds which are known to be hydrologically sensitive, or that agro-environmental subsidies would be made more attractive in these areas.

• Land use planning as an instrument should take into account, to a greater degreethan it does now, the sensitivities of the different physical environments to land use.Land use planning at municipal level could become a powerful instrument topreserve and even create protective land use forms in sensitive areas of a givencatchment. Moreover, in the land use permit legislation, certain catchments or partsof catchments should be labelled as “areas of natural risk” which would automaticallyrestrict a number of land use forms in these areas.

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Most of the proposed measures fit in the framework of at least one legislative tool and nomajor contradictions between proposed measures and existing legislation have beenidentified. This applies to both the Dutch, Flemish and Walloon part of the catchment.Crippling contradictions between legislations have not been found, although manydifferences in focus are present. What has been concluded or recommended on thethree distinct parts in this legal framework study can be extrapolated for the catchmentas a whole.

An integrated approach of the Geul catchment is needed; not only combining the pointsof view of different policy sectors (water-resources management, land use planning,environmental planning, agricultural sector…) and different levels in society (local,provincial and regional or national), but also taking into account the trans-nationalconcerns. For instance, policy-makers and land users in the upstream parts of a trans-boundary catchment should be aware and convinced of taking measures to reduce therisk on flash flood events, and the accompanying mudflow damage, in the downstreampart of the catchment (e.g. consciousness on retaining water in the catchment byenhanced infiltration (pastureland or forest instead of bare fields, less paved surface,dispersion drain pipes instead of ordinary drain pipes…), or on slowing down the water


Legal Framework 152

flow instead of accelerating it (storage reservoirs, constriction devices)). A sustainableand sound land use planning should be established in order to prevent building on flood-prone areas or introducing infrastructure along watercourses. After all, flooding eventshave always existed in the Geul river region and high rainfall events will always remain.The increasing dissatisfaction especially results from the fact that more and moresediments are carried along by the river (increased erosion due to, among other things,maladjusted agricultural practices and land use in the hilly loess region), which aredeposited in often improperly planned urban area during (flash) flood events. Theimportance and need of considering the water system as a guiding principle in land useplanning is obvious.

An elaborated and sound trans-boundary (European) legislative framework andregulations (incentives, taxes) should facilitate both the water retention and erosioncombating in the Geul catchment. A re-valuation of the actual land use in the socio-economic context should also be considered (for instance promotion of other crops,promotion and subsidizing of biologic (small-scale) agriculture). The reader is alsoreferred to Annexe F.1, ‘Awareness-raising measures’, on this part.

The most obvious conclusion one can derive from the analysis of the legislativeframework for the three regions is that no legislation provides a complete set of rules ora clear framework in which to place measures aimed at hydrological control on the riverbasin level. Measures do exist, but they are dispersed over a whole array of laws andregulations. More importantly, limiting the runoff is never a primary goal; it is a secondaryresult of measures that are primarily intended to conserve biodiversity, to combaterosion or to optimise conditions for agriculture. It should also be noted that mostrelevant legislation does not have an area-based perspective. This is regrettable, assuch a perspective could make it possible to use its tools in a spatially integrated way orto apply them selectively to watersheds one wants to protect. The only exceptions tothis, almost by definition, are the land consolidation projects.

It is interesting to note that the legislations that seem to best sustain the proposedmeasures or at least have the potential to do so are both concerned with agriculture, notwith nature or water conservation. Land consolidation projects for instance have an areaapproach and a scale that is ideally suited to implement many of the proposedmeasures. Although their primary goal is to optimise working conditions for agriculture,this does not exclude taking measures that favour water retention, and even provide thefinancial and technical means for doing so. The system of agro-ecological subsidies(following the European directive) is also an attractive instrument that allows for theimplementation of a number of the water retention measures proposed in the presentstudy. Its effectiveness could be further enhanced by providing subsidies for measuresspecifically aiming at increasing water retention and by making it possible to differentiatethe measures eligible for subsidies and even the amount of the subsidies on an areabasis.

Sensitisation and awareness-raising to the need for water retention in the watershedappear to be of paramount importance for implementing most of the inventoriedmeasures, since the most promising measures do depend on the goodwill of the land


Legal Framework 153

users. If measures are to be implemented and sustained in practice, a bottom-upapproach towards the selection of a measure, the location of the implementation of ameasure etc. should be performed with all actors and stakeholders involved(participatory decision-making process).

The reader is also referred to §8.2.4 and §8.2.5 (The Netherlands), to §8.4.4 and 8.4.5(Flemish Region) and to §8.5.4 and §8.5.5 (Walloon Region) for the conclusions,respectively recommendations, on the distinct parts in the Geul catchment.


Conclusions 154

�� &21&/86,216

This report presents the results of the SLORW� SURMHFW (B4-3040/97/730/JNB/C4) IRU� WKHGHILQLWLRQ�RI�HQYLURQPHQW�IULHQGO\�PHDVXUHV�WR�UHGXFH�WKH�ULVN�IRU�IODVK�IORRGV�LQ�WKH�*HXO5LYHU�FDWFKPHQW��%HOJLXP�DQG�WKH�1HWKHUODQGV�.

The study is financed by the European Commission, Directorate-General Environment,and co-financed by the Walloon Regional Government, the Dutch Waterboard Roer &Overmaas and the Belgian Province of Limburg.

The overall goal of the project is to identify environment-friendly measures possiblyapplicable to reduce the risk of flash flood events in the Geul river catchment area, andto study their effectiveness. Within the scope of this overall goal, more specificobjectives are defined:

• Develop a methodology suitable to study the effectiveness of possibly applicablemeasures to reduce the risk of flash flood events at catchment scale, applicable inthe Geul catchment area as well as in other European catchment areas;

• Apply this methodology to study the Geul catchment area:

- identify relevant information and acquire, standardise, store and supply thisinformation to the project partners: WHUULWRULDO�GDWD�LQYHQWRU\;

- perform a preliminary risk analysis;

- bring the international stakeholders together and identify sets of possiblyapplicable measures to reduce the risk of flash flood events: VFHQDULRGHYHORSPHQW;

- study the effectiveness of the scenarios to increase the water retention in thecatchment and to reduce peaks in water flow to the river network: K\GURORJLFDOVWXG\;

- study the effectiveness of the scenarios to reduce the water heights in the rivernetwork, relative to the height of the riverbanks: K\GURG\QDPLF�VWXG\;

- identify the most effective or favourable scenario or set of measures to reducethe risk of flash flood events;

- study the effectiveness and applicability of the legal frameworks and policyinstruments of local-, provincial- and national authorities to support theimplementation of the most favourable set of measures to reduce the risk offlash flood events: OHJDO�IUDPHZRUN.

• Conclude on the effectiveness of the methodology to contribute to the developmentof environment-friendly policies of water management and flood risk reduction in theGeul catchment area;

• Recommend, where necessary, how to ameliorate the methodology to be applicablein other European catchment areas.


Conclusions 155

Project partners originating from all countries located in the Geul river catchment,Belgium and the Netherlands, performed the study. Together they developed andexecuted an appropriate methodology. The methodology is based on a thoroughanalysis of a well-defined reference situation, namely the historic and current land usedistribution, rainfall measurements and measured data on water flow through the Geulriver network. The correct water flux simulation in this reference situation permits thesimulation of water flow in hypothetical situations or scenarios.

The regional stakeholders (the Walloon Regional Government, the Dutch WaterboardRoer & Overmaas and the Belgian and Dutch Provinces of Limburg) participated in thepresent study by providing the necessary information, input for further study, and byassisting in the decision-making process during the scenario development.

Five scenarios were developed for further study, including land use measures to betaken in the watershed and civil-technical measures to be taken in the river itself. CSOand FSAGx performed the territorial data inventory, harmonized the internationallyacquired data into one format and developed a Geographical Information System (GIS)for data storage, data analysis and data input for the other study items. CSO alsodescribed the area and set the reference for further study by performing a preliminaryanalysis of the cause for land runoff. The University of Liège, in collaboration with theUnit of Agricultural Hydraulics FSAGx, performed the hydrological study. They analysedthe effectiveness of the land use scenarios, simulating the amount, timing and location ofrunoff to the river network as a function of climate, hydrogeology, soil and land usescenario. Technum, in cooperation with IMDC, performed the hydrodynamic study. Theyanalysed the effects of the land use scenarios, simulating the level and timing of waterflowing through the river network as a function of the runoff, simulated in the hydrologicalstudy. The hydrodynamic simulation also served to analyse the effectiveness ofscenarios of civil-technical measures, implemented in the upstream parts of the riverbed.Technum also studied the legal framework and was involved in the project management.

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Relevant data were acquired in all three countries located in the Geul river catchmentarea (Belgium, The Netherlands and Germany). The internationally diversified sources ofinformation were associated with considerably diversified classification systems (e.g.soil- and land-use classification), reference systems (e.g. units of measurement,geographic map projections and map co-ordinates) and storage formats. Consequently,data harmonisation was very time-consuming and led inevitably to additionaluncertainties. It is therefore highly recommended to initialise a standardisation ofgeographic databases (GIS) with standardised and coherent data within Europeancountries.

A Geographic Information System (GIS) was developed for data storage and furtherstudy (ZKLFK�UHTXLUHV�WKH�H[SOLFLW�DXWKRULVDWLRQ�RI� WKH�)6$*[�DQG� WKH�6(7+<��6HUYLFHG¶pWXGHV�GX�0LQLVWqUH�ZDOORQ�GH� O¶(TXLSHPHQW� HW� GHV�7UDQVSRUWV�� IRU� WKH�&$5+<�GDWD


Conclusions 156

EDVH� *,6). The ESRI software packages Arc-Info and ArcView were used for thispurpose. The GIS includes a topographic map of the area, a soil map, an elevation map,a hydrological map and a current land use map. Secondary maps were derived fromthese base maps, including a hydrological soil group map, a slope map, a historical landuse map of the 1950’s etc. Dividing the GIS map layers into geographic grid-cells of30x30m set the degree of detail. The GIS proved a valuable tool to perform geographicanalyses.

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The maps were used to describe the area and were used for a preliminary risk analysis.The analysis led to the determination of trends between the historic and current risk ofrunoff at catchment scale following two methods (simplified Wischmeier USLE methodand the US SCS method). The USLE procedure implied a land use systems analysis,based on parameters derived from the Universal Soil Loss Equation. Literature reviewserved to quantify the parameters explaining the risk of surface runoff in relation withsheet and rill erosion (including partly aspects of land erosion), slope and land use (landcover and land management practices). Besides these aspects, the SCS method alsoincludes soil humidity and soil type.

The results suggested an increase of the risk of runoff on arable land. Although itsacreage did not change since the 1950’s, its contribution to the risk increased becauseof the increased proportion of weeded crops. The quantification of these risks is made inthe hydrological analysis.

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The analysis of the availability and reliability of rainfall and water discharge data(observations at meteorological and limnimetric stations) shows:

• a limited number of pluviographs, affecting the knowledge of spatial distribution ofhourly rainfall;

• abnormally low or high values at some meteorological stations and periodicallymissing data.

Insofar as the basic data can be considered as being reliable, the preliminaryhydrological analysis provides the following conclusions:

• in general, mean annual flow and flow coefficients are small (around 30% or less,including during flood events) with respect to usual evapo-transpiration rates for thisarea; low annual flow coefficients for the tributaries of the Geul are observed,suggesting a "loss" of water;


Conclusions 157

• the flood rise time is short (2 to 4 hours in the central part of the basin; phase-lag of4 to 10 hours at the outlet), related to the shape and topography of the watershed;

• peak flows show normal values (200 l/s.km2 at Hommerich) but a damping of thepeak flows is observed at the outlet (100 l/s.km2 at Meerssen).

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A preliminary list of 46 possibly applicable measures to reduce the risk of flooding wasestablished on the basis of literature review, preliminary analysis and brainstormsessions. This number was reduced to a number of five scenarios, which were subjectfor further study. The regional stakeholders were involved in the identification-process ofthis limited number of scenarios.

Two reference scenarios were defined: the current and historical land use situation. Theother three scenarios represent possibly applicable measures to reduce the risk offlooding from its current level to the “historic” level or even further. The project teamexpects that an integrated approach of water management at the catchment scale wouldsignificantly reduce the risk of flash flood events in downstream, flood-prone areas.

The scenarios have an environmental dimension, reflecting interventions in the land usedistribution to improve water retention in the catchment, and a civil-technical component,reflecting interventions in the riverbed itself to improve water retention in the upstreampart of the river network. The scenarios, identified for simulation in the hydrological andhydrodynamic studies, were:

6FHQDULR /DQG�PDQDJHPHQW 5LYHU�PDQDJHPHQW

�. 1990 reference Present land use Present situation

�. Scenario 2 Grass on slopes >12% Increased roughness of the river flood plains

�. Scenario 3 Forest on slopes >10% Present situation

�. Scenario 4 Greenbelts / hedgerows Addition of 2 constriction devices in the riverbed

�.1950 reference Land use of the 1950’s Present situation

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The effectiveness of the land use scenarios to reduce the water runoff to the rivernetwork was studied in the hydrological study by means of a lumped dynamic simulationmodel (the hydrological part of the model MOHICAN, developed by ULg and FSAGx).The hydrological model is composed of a soil sub-model (EPIC-GRID) and agroundwater sub-model (which utilizes a groundwater impulse response transferfunction). The model computes water fluxes from the soil to the river network, from the


Conclusions 158

soil to the groundwater, and from the groundwater to the river network (base flow). Theoutput also serves as input for the hydrodynamic study.

The model needs no calibration. The model has been validated, including the role ofgroundwater, under the current situation on the (continuous) period 1993-1998 (forwhich detailed data are available). This period includes the five major flood events thatrecently occurred in the Geul basin. The conclusions obtained are that the hydrologicalmodel is able to simulate the hydrological behaviour of the watershed, including thegroundwater transfers. Additional data must however be collected to assess preciselythe possible losses of groundwater from the Gulp (and maybe from other tributaries) tothe alluvial plain of the Meuse river.

As the hydrological model uses physically-based representations, it has been concludedthat the model is able to simulate runoff and base flow for changes in land use oragricultural practices. The model has thus been used to simulate the different scenariosand to assess the effectiveness of the proposed land-related measures. The results showthat the proposed environment-friendly measures do reduce the duration and fluxes ofwater to the river network under high rainfall events, but only weakly: the reduction ismaximum 10%. In general, scenario 3 (transformation of farming and pastureland withslopes higher than 10% into forest) and land-related measures of scenario 4(transformation of all farming land into farming land with green belts) show the highestimprovements as regards daily water flux reduction. These scenarios give more or less thesame result as the simulation of the historic land use scenarios of the 1950’s.

The simulated scenarios, especially the land-related measures of scenario 4 (farming landwith green belts and hedgerows), are also favourable to decrease local erosion problems(gullies). This erosion problem would need some further (specific) elaboration.

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The effectiveness of the scenarios on reducing the risk of flooding was studied in detailin the hydrodynamic study. The timing and location of the discharge (m³/sec) and theheight (m) of the water flowing through the Geul river and its tributaries were simulatedas a function of the water runoff calculated by the hydrological model. The ISIS Flowmodel is used as hydraulic simulation model. The results were plotted along alongitudinal profile of the Geul river, relative to the height of the riverbanks. Analysispermitted to conclude where the flood-prone areas are located and which scenarioappears most favourable to reduce the risk of flash flood events.

Currently, major flooding problems occur upstream of the mills: Volmolen, Epermolen,Bovenste Molen, Wijlre, Oude Molen, Franse Molen and Groote Molen. Other flood-prone areas are the Geul river in Wallonia near the Dutch border, and the Geul river atthe mouth with Eijserbeek and Gulp. The effectiveness of the land use measures, aimedto retain water in the uplands and to reduce the peaks of water runoff to the river


Conclusions 159

network, proved insufficient to prevent flooding. Peaks in river water discharge weremaximally reduced by 10% for the historic land use scenario of the 1950’s (as obtainedin the hydrological study). Peaks in river water heights were maximally reduced by 22cm.

The installation of two constriction devices in the upstream parts of the Geul river,combined with land-related measures (all farming land with green belts or hedgerows),reduces the peak river water discharges by maximum 17%. This proved to be the onlyscenario with water heights in the Geul river generally below the heights of theriverbanks; however, it cannot guarantee the FRPSOHWH prevention of flooding problems.

This allows concluding that the flood problems in the Geul catchment are caused by acombination of climatic events, modifications of land use and agricultural practices, andmanagements operations in the riverbed (straightening, suppression of JUDIWHQ).Combining land-related measures with civil-technical measures in the river is thusnecessary to reduce the risk of flash flood-related inundations along the Geul river.

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The legal framework and policy instruments at the disposal of local, provincial andnational authorities in the three parts in the catchment were studied to assess theirapplicability for promoting and implementing the environmentally-sound measuresstudied here above. The instruments are multilateral and have been found in manysectors (water-resources management, land use planning, environmental planning,agricultural sector…). Important conclusions are that involvement and initiative of thepolicy-makers and stakeholders of all these sectors is of extreme importance, and trans-national cooperation is highly required.

Most of the proposed measures fit in the framework of at least one legislative tool and nomajor contradictions between proposed measures and existing legislation have beenidentified. This applies to both the Dutch, Flemish and Walloon part of the catchment.Crippling contradictions between legislations have not been found, although manydifferences in focus are present.

No legislation provides a complete set of rules or a clear framework in which to placemeasures aimed at hydrological control on the river basin level. Measures do exist, butthey are dispersed over a whole array of laws and regulations. More importantly, limitingthe runoff is usually no primary goal; it is a secondary result of measures that areprimarily intended to conserve biodiversity, to combat erosion or to optimise conditionsfor agriculture. It should also be noted that most relevant legislation does not have anarea-based perspective. This is regrettable; as such a perspective could make itpossible to use its tools in a spatially integrated way or to apply them selectively towatersheds one wants to protect. The only exception to this, almost by definition, are theland consolidation projects.


Conclusions 160

The legislations that seem to best sustain the proposed measures or at least have thepotential to do so are both concerned with agriculture, not with nature or waterconservation. Land consolidation projects for instance have an area approach and ascale that is ideally suited to implement many of the proposed measures. Although theirprimary goal is to optimise working conditions for agriculture, this does not excludetaking measures that favour water retention, and even provide the financial and technicalmeans for doing so. The system of agro-ecological subsidies (following the Europeandirective) is also an attractive instrument that allows for the implementation of a numberof water retention measures proposed in the present study. Its effectiveness could befurther enhanced by providing subsidies for measures specifically aiming at increasingwater retention and by making it possible to differentiate the measures eligible forsubsidies and even the amount of the subsidies on an area basis.

Sensitisation and awareness-raising to the need for water retention in the watershedappear to be of paramount importance for implementing most of the inventoriedmeasures, since the most promising measures do depend on the goodwill of the landusers. If measures are to be implemented and sustained in practice, a bottom-upapproach towards the selection of measures, the location of the implementation of ameasure etc. should be performed with all actors and stakeholders involved(participatory decision-making process). It is absolutely required to spend enoughattention on the supply of information and sensitisation.

Finally, the applicability of many instruments is limited due to factors like limited financialresources and limited possibilities to expropriate privately owned land. Cooperationbetween sectors and authorities is not only required for effective use of the instrument,but also for further investigation and elaboration on the potencies of the instruments.

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The hydrological model proved to be effective to simulate the hydrological behaviour ofthe watershed, including groundwater transfers, despite some basic data (rainfall,discharges) being incomplete or questionable. Uncertainties however still remain,associated with possible losses of groundwater from some tributaries of the Geultowards the alluvial plain of the Meuse river. Nevertheless, the model results wereaccurate and the simulation results reacted sensitively to small changes in input, so thatthe effectiveness of the proposed land-related measures could be assessed.

The hydrodynamic model calculated the discharge and the height of the water in theGeul river and its tributaries. The study located the flood-prone areas and investigatedwhich scenario being favourable to reduce the risk of flash flood-related inundations.


Conclusions 161

The ‘cultivation’ of green belts and hedgerows in farming land provides an effective, butsmall, reduction of water fluxes to the river network under high rainfall events. Thecombination with the installation of constriction devices in the upstream riverbeds,proved effectively reducing peaks in river water height compared to the height of theriverbanks, and thus reducing the risk of flash flood-related inundations along the Geulriver.

The introduction of green belts and hedgerows in agricultural parcels, although having initself a relatively small effect on flash floods, is complementary useful to reduce theerosion from agricultural fields.


Recommendations 162

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An integrated approach towards water management at catchment scale is highlyrecommended to reduce the risk of flash flood events. Such a policy must be based onthe results of a global analysis (hydrology, hydraulics) and has to tackle the causes,while ameliorating the water retention capacity of the watershed and the river. Effortsshould be directed at making possible minor but effective changes to the existinglegislation, and to better co-ordinate actions between responsible administrations.

The integrated approach should not only combine the points of view of different policysectors (water-resources management, land use planning, environmental planning,agricultural sector…) and different levels in society (local, provincial and regional ornational), but also take into account the trans-national concerns. For instance, policy-makers and land users in the upstream parts of a trans-boundary catchment should beaware and convinced of taking measures to reduce the risk on flash flood events, andthe accompanying mudflow damage, in the downstream part of the catchment (e.g.consciousness on retaining water in the catchment by enhanced infiltration (pasturelandor forest instead of bare fields, less paved surface, dispersion drain pipes instead ofordinary drain pipes…), or on slowing down the water flow instead of accelerating it(storage reservoirs, constriction devices)). A sustainable and sound land use planningshould be established in order to prevent building on flood-prone areas or introducinginfrastructure along watercourses. After all, flooding events have always existed in theGeul river region and high rainfall events will always remain. The increasingdissatisfaction especially results from the fact that more and more sediments are carriedalong by the river (increased erosion due to, among other things, maladjustedagricultural practices and land use in the hilly loess region), which are deposited in oftenimproperly planned urban area during (flash) flood events. The importance and need ofconsidering the water system as a guiding principle in land use planning is obvious.

An elaborated and sound trans-boundary (European) legislative framework andregulations (incentives, taxes) should facilitate both the water retention and erosioncombating in the Geul catchment. A re-valuation of the actual land use in the socio-economic context should also be considered (for instance promotion of other crops,promotion and subsidizing of biologic (small-scale) agriculture).

International cooperation is highly required. The Declaration of Arles, undersigned by theMinisters of Environment of France, Germany, Belgium, Luxembourg and TheNetherlands, is a good starting point for the “new approach”. In this declaration, theMinisters officially declared that they deemed it necessary to reduce flood-related risksas rapidly as possible. Water retention should become one of the most importantprinciples of water management. The policy- and instruments development regarding thecurrent flood problems should be co-ordinated at catchment level.

Among the possible management measures, the transformation of farming land withslopes higher than 10% into forest and the introduction of green belts and hedgerows in


Recommendations 163

agricultural fields, in combination with the installation of constriction devices in theupstream riverbeds, are recommended, as they proved effectively reducing peaks in theriver network under high rainfall events (while also reducing erosion from the agriculturalfields).

Following the performed analysis and the obtained hydrological results, it isrecommended:

• to increase the availability and reliability of data (rainfall, river discharge,characterisation of urban areas);

• to investigate by additional measurements and hydrogeological studies the questionof possible direct losses of groundwater from the Geul catchment (especially fromthe tributaries of the Geul) towards the alluvial plain of the Meuse river.

In the future, the problem of soil erosion in the Geul basin should be addressed as aproblem in itself (and not just in relation to flood events).

For future hydrological studies, it is recommended to pursue the utilization of thehydrological model MOHICAN, as it has proved to efficiently simulate the hydrologicalbehaviour of the watershed, including groundwater transfers. Additional advantage isthat this model simulates the topsoil dynamics and the crop growth.

Harmonizing GIS data and improving the availability of these data within Europe couldsignificantly improve the quality and reliability of the results obtained in trans-boundaryprojects. It could also save a lot of time and money on comparable projects in the future.As part of this report, the GIS team suggests the following to local, national, andEuropean Union officials:

• A central European databank of unified meta-data should be created.

• GIS data should be made more affordable in Europe.

• Agreements concerning user rights and user restrictions should be made betweengovernment authorities to clarify the data exchange.


References 164

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The references to the literature used in this report are given in the Annexes.

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