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Implementation of MIKE URBAN and MOUSE to Support Sustainable Economic and Quality Assurance in the Municipal Water Company in Egedal - Denmark

Sabah Al-Shididi

MSc Environmental Eng., MSc Environmental Policy, BSc Civil Eng., Egedal Municipality, Miljøcenteret (Center for the Environment), Kloakforsyningen (Urban sewer supply), Rådhustorvet 2, 3660 Stenløse, Denmark, tel. +45 7259 7312, +45 2068 9742, sabah.al-shididi@egekom.dk

Abstract

Climate change is an extensive challenge for water companies to optimize drainage systems capacity. Publications of The Wastewater Committee in Denmark no. 27, no. 28 and no. 29 are the recently updated guidelines for hydraulic design of drainage systems in Denmark. Private housing developments are the most typical means of drainage systems expansion. Renovation and reconstruction projects consider higher capacity in drainage systems due to future scenarios of climate change, continuous expansion of impermeable urban quarters and increased restriction on discharge permission according to new water plans in Denmark.

The Municipal Water Company in Egedal implemented MOUSE/MIKE URBAN, as a successful tool for quality assurance for private housing development projects. MIKE URBAN helped to obtain sustainable economic measures in renovation projects in accordance with the water company perspective. More than 6 million DKK (€ 0.8 million) were saved by The Municipal Water Company in Egedal (MWCE) during 2007.

Key words

Egedal, MIKE URBAN-MOUSE, SVK, housing development projects, renovation projects, Water Company, MWCE.

Introduction

Egedal Municipality was born on January the 1st 2007 by merging the three previous municipalities Stenløse, Ølstykke and Ledøje-Smørum. The population concentration of Egedal is 320 people per km2. The approximate population is 40,000 people and the area is approximately 125 km2. The recent technological developments in the water sector are implemented in Egedal. The major towns are Stenløse, Ølstykke, Smørum and Ganløse as shown in Figure 1. The sewer system in the urban areas is 80% separate system and 20% combined system with in total approximately 722 km of sewer pipe. There are 100 detention tanks in form of basins, underground tanks, detention pipes, lagoons and lakes.

In the past four years, Egedal was exposed to two rainfall events in summer 2005 and summer 2007, which caused flooding in some areas. MIKE URBAN-MOUSE has been implemented since then for hydraulic analysis, design, planning and as well as economic analysis of the drainage system in Egedal. This paper is a review and analysis of the hydraulic modeling experience of the MWCE by implementing MIKE URBAN-MOUSE. Furthermore, the paper presents case studies, results, conclusions, decisions and future plans for implementing hydraulic modeling in the water company.

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Figure 1: Map of Egedal showing the borders and names of the old municipalities and towns.

Guidelines of hydraulic design of drainage systems in Denmark (SVK 16)

In order to understand the hydraulic design requirement of sewer systems in Denmark, which the MWCE has adopted as an objective in housing development and renovation projects, the design guidelines, will be presented.

Publication no. 16 of The Wastewater Committee in Denmark (SVK 16) of 1974 under the title “Determination of rain series“ has classified rainfall events in Denmark of 1 year, 2 years, 5 years,…etc. rain events [SVK 16, 1974]. The letter “T” was given to refer to the rain event. For example, T=20 is a 20 year rainfall event, which statistically is expected every 20 years. The statistics were based on observation period 1933-62 [Winther et.al, 2005, p87]. Curves of precipitation events of different durations from SVK 16 are shown in Figure 2. The rain event of T=1 (6.6 mm) and T=2 (8.4 mm) in 10 minutes were typically used to design full-flow sewer pipes of separate system and combined systems respectively [Winther et.al, 2005, p224; DS 432, 1994].

Figure 2: Curves of rainfall events of different durations based on observation period 1933-62 from SVK 16 [Al-Shididi, 2008].

Ølstykke

Stenløse

New Ølstykke

Veksø

Ganløse

Slagslunde

Smørum

T= 1, 2, 5, 10 and 20 rain events of different durations

according to SVK 16 of 1974

6,6 8,4

11,4 13,8

0 5

10 15 20 25 30 35 40 45 50

5 10 15 20 25 30 40 60 120 Duration of rain event

(min.)

T=1

T=2

T=5

T=10

T=20

Inte

nsit

y (

mm

) o

r (l

/m2)

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The pipe is designed to have the capacity of discharging every rain event that happens on and below the curve in figure 2 with a level of water not higher than the top of the pipe. This was the guideline for hydraulic design of drainage pipes in Denmark until SVK 27 of October 2005 “Function practice of drainage systems under rain” defines additional guidelines.

Guidelines due to climate change (SVK 27)

Higher intensity of rainfall events has been observed in the last 10 years, which can be possibly ascribed to climate change. Due to this fact SVK 27 defines an allowed maximum level of water above the sewer pipes as an additional guideline for drainage systems hydraulic design as is shown in figure 3.

Figure 3: Illustration of guidelines for hydraulic design of separate and combined drainage systems according to SVK 27 [Al-Shididi, 2008a].

Definition of the terrain level, especially in combined systems, depends on what is the lowest, the road level or the level of the ground floor of the house.

SVK 27 also discusses factors of safety in future sewer systems due to different scenarios of climate change, increase in percentage of impermeablity and possible inaccuracy in calculation. Estimation of the safety factor takes into consideration the economic aspect. The economic aspect is discussed as a balance between cost of executing/operating and cost of renovation. The SVK 27 conclusion is that a total safety factor can fluctuate between 1.2 and 1.7, which means higher hydraulic capacity. SVK 29 of August 2008 “Expected changes in extreme rainfall following climate change“ suggests a total safety factor between 1.45 and 1.7. Of this total safety factor, the climate factor represents 1.2, 1.3 and 1.4 of respectively 2, 10 and 100 years’ scenario or lifetime of drainage system.

The choice of the factor according to SVK 27 depends on the following:

Terrain

T=1

T=5 T=10

T=2

According to SVK 27 the maximum water level is the terrain level under T = 10 (13.8 mm in 10 min.)

Design of combined system is full-flow pipe under T = 2 (8.4 mm in 10 min.)

Combined

Rainwater

According to SVK 27 the maximum water level is the terrain level under T = 5 (11.4 mm in 10 min.)

Design of rainwater system is full-flow pipe under T = 1 (6.6 mm in 10 min.)

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1. Type of chosen climate scenario.

2. Level of calculation (Level 1 based on block rain, level 2 based on CDS-rain1 and historical rain or level 3 based on verified model).

3. The degree of condensation in catchments, which is the prospect in terms of percentage of expanded impermeable areas particularly in urban areas.

4. The chosen level of service that the water company intends to provide in terms of definition of terrain level (critical level) especially in modeling of existing drainage system.

Furthermore, SVK 28 of 2006 has included rainfall events registered from 97 rain stations distributed across Denmark. This has shown that there is an increase in rainfall intensity up to 20% in the past 10 years [SVK 28, 2005, p22-25], which added an extra safety factor. Figure 4 shows the relation between new rain series (1979-2005) and previous rain series from SVK 26 (1979-1997).

Figure 4: Regional estimate of T-year intensity in a location in Region East with average annual precipitation of 600 mm based on the data from SVK 28 (1979-2005) and the data from SVK 26 (1979-1997) [SVK 28, 2006, p25] .

The art of planning and management engineering is to provide not less than the minimum level of service that complies with guidelines and at the same time to achieve the lowest point in the curve of the total cost in figure 5. This is a strategic goal for the MWCE.

Based on the above-mentioned strategy, the MWCE has adopted a management policy of construction and renovation of drainage systems.

In order to realize this policy, a hydraulic analysis tool was necessary. The MWCE has chosen the DHI’s MIKE URBAN and MOUSE as a tool to support decision-making processes in planning, designing and choice of solution of specific projects and thus to facilitate economic optimization.

1 CDS-rain is Chicago Design Storm [SVK 28, 2005]

Duration [min.]

Rela

tio

n b

etw

een n

ew

and p

revio

us e

stim

ate

s

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Figure 5: The basic principle of economic optimization regarding the relation between the construction and renovation cost converted to an average annual cost as a function of return period [SVK 27, 2005, p16; Winther et.al., 2006, p228].

Fields of implementation

MIKE URBAN and MOUSE have been implemented primarily into specific projects, such as housing development projects and renovation projects. The decision was taken to focus on implementing hydraulic modeling in specific projects planning rather than in general planning. The decision-making was based on the economic significance of specific projects that can economically be estimated by such analysis as hydraulic evaluation.

Two types of specific drainage system projects the MWCE has carried out. The two types will be presented in the following:

1. Private housing development projects

This type of project is the typical mean of expansion of drainage systems in Egedal. In development projects the MWCE comes to an agreement with the private, official or municipal client that owns the housing project to construct the drainage system on behalf of and according to the specifications of the MWCE. The cost of the sewer system is born by the MWCE. The process starts with sending the project to the MWCE for approval. The approval process includes the following:

a. Examination and approval of project plans.

b. Examination and approval of the structural design of the drainage system.

c. Examination and approval of project calculations usually made by the rational method.

d. A hydraulic evaluation carried out by the MWCE on level 2 calculation of SVK 27.

e. Assessment and approval of the quantities of the project.

Economic optimization

Cost of renovation

Cost of construction and operation

Cost

Return period

Total cost

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f. Estimation and approval of economic compensation based on the above approvals.

g. Signing of a handover agreement of the project to the MWCE according the specifications of the MWCE. The handover happens at the end of the project.

2. Renovation projects

This type of project is carried out by the MWCE. The project starts with investigations, evaluation, solution proposal, bidding, contracting, construction and the handover. The solution proposal is usually based on hydraulic evaluation. The MWCE carries out or orders a MIKE URBAN-MOUSE model and then performs a quality check on the model before it is implemented in solution proposal.

Case studies

Case studies from six projects will be presented in this review from both housing development and renovation projects such as the following:

1. Housing development projects: Peter Appelsvej, Stenløse Syd (Stenløse south), Trianglen (The triangle).

2. Renovation projects: Detention pipe in Veksø, Flooding control in Ganløse, Renovation project in Smørum.

Peter Appelsvej

A 42 house development project with separate drainage system with a 345 m3 rainwater detention basin was executed on the north-western edge of Ganløse town. During the submission phase of the project to the MWCE, the initial costs of the project were estimated by the client’s consultant at about 3 million DKK (€ 0.4 million) [Stenløse, 2006, p6]. By revaluating the project both hydraulically implementing MIKE URBAN-MOUSE, qualitatively and quantitatively, the cost of the project was reduced to less than 1.7 million DKK (€ 0.23 million). The project and one of the solutions are illustrated in figure 6.

The project, following to the design of the client, was exposed to flooding under T=5, which does not fulfill the requirements of SVK 27. In order to optimize the project level of service, the following was applied by the MWCE:

• Necessary adjustments of pipe dimensions were carried out.

• Reduction of the number of manholes from 32 to 28.

• Change of the design of the inlet/outlet of the basin.

• Removal of tide flex valve.

• Flexibility was given to the contractor to choose the approved environmentally-friendly materials.

The following results were achieved:

• The project lived up to the guidelines of SVK 27 of maximum water level to the terrain under rainfall event T=5.

• 55 m3 extra volume capacity was achieved in the detention basin.

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• The discharge of the catchment was adjusted to 2.5 l/s to comply with the allowed maximum annual average discharge of 2.7 l/s (2 l/s/red.ha) according to the official Wastewater Plan 2001-2012 [Stenløse, 2006, p3].

• 1.3 million DKK (€170,000) were saved.

Figure 6: An example from the housing development project Peter Appelsvej, Ganløse, Egedal, Denmark. The pipe series 1-2 turned out to be vulnerable to flooding during rain event T=5. The design was adjusted by The Municipal Water Company in Egedal as shown in Profile b. Level 2, CDS-rain according to SVK27 was used in modeling.

Stenløse Syd (Stenløse South) - phase II

The project started in fall of 2006, which was a housing development project of approximately 500 houses on 30.2 ha (12.1 red. ha) with 5 detention tanks [Stenløse, 2004]. Egedal Municipality itself was the client of the project, which was under the supervision of the MWCE. Allowed maximum annual average discharge from the catchment is 2 l/s/red.ha (24 l/s) [Stenløse, 2004].

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0 140.0

[m]

38.5

39.0

39.5

40.0

40.5

41.0

41.5

[m]

Link Water Level - 4-6-2006 13:06:58 Simulation_1Base.PRF

R2.

1R2.

2.1

R2.

2.2

R2.

2.3

R2.

2.4

Ground Lev.

Invert lev.

Length

Diameter

Slope o/oo

[m]

[m]

[m]

[m]

39.8

1

40.2

0

40.4

9

41.0

9

38.4

8

38.8

1

38.9

9

39.6

5

29.18 13.35 60.34 36.18

0.23 0.19 0.19 0.15

11.31 13.48 10.94 13.27

m3/sDischarge 0.051 0.041 0.033 0.011

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0 140.0

[m]

38.6

38.8

39.0

39.2

39.4

39.6

39.8

40.0

40.2

40.4

40.6

40.8

41.0

41.2

41.4

[m]

Link Water Level - 4-6-2006 13:05:58 Simulation_1Base.PRF

R2.

1R2.

2.1

R2.

2.2

R2.

2.3

R2.

2.4

Ground Lev.

Invert lev.

Length

Diameter

Slope o/oo

[m]

[m]

[m]

[m]

39.8

1

40.2

0

40.4

9

41.0

9

38.4

8

38.8

1

38.9

9

39.6

5

29.18 13.35 60.34 36.18

0.28 0.22 0.22 0.17

11.31 13.48 10.94 13.27

m3/sDischarge 0.065 0.055 0.047 0.016

1 2

Profile a

Received from the client

Profile b

The solution proposal of the MWCE

2

1

Basin

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In order to proactively deal with the increasing intensity of rain observed in the past decade, a new concept was implemented in the municipality. The concept reuses the roof water (Rain water) in toilet flushing and infiltrating the surplus water locally through the ground of each property. Only road water (Rain water) is discharged into the drainage system [Stenløse, 2004]. The project is presented in figure 7.

Figure 7: Project information of Stenløse Syd (Stenløse South) – phase II from MIKE URBAN-MOUSE.

The MWCE has examined the project on level 2 calculation, CDS-rain according to SVK 27 guidelines. It was found that the road surface in the location marked with the dotted circle in figure 8 was 38 cm (level 16.98 m) below water during a T=5 rain event. See figure 8 for details. The location was vulnerable because a heating power station was scheduled to be constructed just to the south west of the location.

Figure 8: Hydraulic analysis by MIKE URBAN – MOUSE of StenløseSyd (Stenløse South) – Phase II project has shown that Manhole R3.2 (Ground level 16.6) in the road Stamvej becomes flooded by 38 cm (Level 16.98) water level during a T=5 rain event. Level 2, CDS-rain according to SVK27 was used.

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To overcome this problem, while the project was under construction a solution was proposed by the MWCE to keep the water level below the ground level of manhole R3.2 during a T=5 rain event. At the time of modeling all pipes upstream of manhole 3.2 were constructed. Furthermore, the pipe upstream manhole 3.2 was in contrast to the project plans executed to 300 mm instead of 250 mm, which resulted in an even higher level of water over manhole 3.2 at level 17.12 m (52 cm). The solution was therefore to raise the ground level of manhole 3.2 and the surrounding terrain to 17.15 m, which was approved. Figure 9 illustrates the eventual solution.

Furthermore the allowed annual maximum average discharge of the whole catchment of Stenløse Syd – phase II was found to be 15 l/s, which is within the allowed discharge of 24 l/s.

Trianglen (The Triangle)

This project was an interesting exercise in modeling an untraditional separate drainage system. The outlet of the catchment of both wastewater and rainwater is located to the south of the catchment. The wastewater pipe net slopes down to the south, while the rainwater system drops to, and is collected in, a detention pond in the north side of the triangulated catchment. This is because the terrain in this catchment slopes down towards the north and the only place to site a detention tank was in the north edge, as illustrated in figure 10. The pond is drained by pumping up water to the outlet. When the pond is filled to the maximum level, a weir at the same level placed in the catchment outlet in the south side, discharges the system downstream. The project was modeled in 2006 and executed in 2007.

Figure 10: Project information of Trianglen (The Triangle) a housing development project of 21 houses, with a detention pond to the north and outlet to the south.

Figure 9: The eventual solution Stenløse Syd (Stenløse South), where ground level at manhole 3.2 in the road Stamvej is lifted up from level 16.6 to 17.15 that the water level became lower than the ground level during the rain event T=5.

The primary pipe belongs to the MWCE. The rest is private net.

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The system has passed the test at calculation level 2, CDS-rain according to SVK 27 on the primary pipe, which belongs to the MWCE.

The rest of system is private and owned by the local housing union. The model during T=5 rain event has shown that there is flooding on the private side of the system, as shown in the longitudinal profile of Figure 11. Even so the flooding had a minor effect, as it is located in the road and parking areas. The client took this problem into consideration and a permeable area was reduced by using semi-impermeable surfacing, which had eliminated the flooding.

Figure 11: A longitudinal profile of the pipe series between flag 1 and flag 2 in the presented catchment map shows flooding during T=5 CDS-rain.

Detention pipe in Veksø

Ten houses in 2006 were added in the upstream catchment at flag 1 in figure 12b. The connection point to the downstream system is flag 2 in figure 10. Need for a detention tank was inevitable to avoid overload on the downstream catchments. A proposal for a project of a detention pipe was submitted to the MWCE in fall of 2005, which was tested hydraulically during the T=5 rain event, CDS-rain. The result is shown in figure 12a. However, there was slight flooding in the downstream pipe.

a) Proposal b) Model

c) Alternative solution

Figure 12: Results of modeling of a detention pipe in Veksø.

a) Model plan in MOUSE.

b) Proposed solution – profile during T=5.

c) Alternative solution – profile during T=5.

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The MWCE has chosen an alternative solution (Figure 12c) that can eliminate the slight flooding to comply with the guidelines of SVK 27 and to use different pipe diameters that could reduce the cost of the project.

Flooding control in Ganløse

A storm of 30 mm precipitation in 40 minutes on 2 June 2005 has hit the combined sewer catchment GA4 in Ganløse with rainfall that caused flooding in private properties. The rain event was equivalent to a 20 year rain event (T=20). Blue circles in figure 13 are water at ground level and red circles are water in basements in figure 11. A longitudinal profile of an externally ordered hydraulic model of the area in figure 11 shows a bottleneck of flooding in the most affected spot on the trunk sewer of the catchment [Al-Shididi, 2006].

Figure 13: Illustration of flooding in catchment GA4 in Ganløse, Egedal on 2 June 2005 of 30 mm in 40 min. (T=20). Longitudinal profile from MOUSE model shows the flooding in the trunk sewer of the catchment. A hydrograph shows the rainfall event [Al-Shididi, 2006].

The flooding data in figure 13 was collected from the local inhabitants in catchment GA4. The calibration of the model was based on this data. The model was based on catchment impermeability of 35% and initial concentration time of 7 minutes. The requirement of the guidelines for this combined catchment was to prevent flooding during a 10 year rain event (T=10). Terrain level is road level in this case. The status and the solution models were tested under both CDS-rain of T=10 and historical rain series.

The solution, which was also externally ordered, was reported in 2006, which included a combination of several solutions, which is listed below and as it is numbered in figure 14:

1. Capacity optimization of an existing detention tank.

2. New detention tank of 750 m3.

3. Increasing the dimension of an existing pipe.

600.0 650.0 700.0 750.0 800.0 850.0 900.0 950.0 1000.0 1050.0 1100.0

[m]

29.0

30.0

31.0

32.0

33.0

34.0

35.0

36.0

[m]

Hovedledning - 3-6-2005 22:26:37 gan-S-3juni.PRF

Grimskær

Langtoften

Abildtoften

Måløvvej

6032

044

6032

046

6032

002

6014

304

6014

302

6014

300

6014

298

6014

299

6014

290

6014

272

6014

270

6014

268

6014

266

6014

264

6014

262

6014

260

6014

158

6014

156

6014

154

6014

152

6014

150

6014

148

6014

146

6012

086

6012

084

6012

082

6012

080

6012

078

6012

076

Length

Diameter

Slope o/oo

[m]

[m]

38.53 40.94 55.99 54.21 67.06 51.15 53.99 52.14 61.49 49.00

0.70 0.70 0.90 0.90 0.50 0.70 0.70 0.70 0.70 0.70

1.56 6.60 2.32 2.77 22.67 2.54 2.78 3.26 4.07 4.29

m3/sDischarge 0.266 0.382 0.382 0.381 0.451 0.452 0.452 0.452 0.590 0.591Rainfall event curve

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4. Reorienting the outlet of 1 ha from catchment GA4 towards another catchment that has sufficient capacity.

Figure 14: The locations of the 4 solutions to overcome the flooding problem of June 2005 in catchment GA4 in Ganløse. A longitudinal profile of the solution shows that the flooding disappears above the trunk sewer [Al-Shididi, 2006].

The solution project was executed in fall 2006 and handed over in summer 2007.

Renovation project in Smørum

The catchment Tulipanhave (Tulip Garden) that is shown in figure 15 had its turn for renovation by 2007. Planning of a renovation project was started in May 2007. The planning started by ordering externally a MOUSE model to investigate whether the catchment satisfies the requirements of SVK 27. The model was ordered without calibration. The catchment is separate and therefore the focus in the hydraulic model will be on the rainwater system.

The focus in this case study will be on a 1100 m trunk rainwater sewer pipe that is highlighted in figure 15.

Figure 15: Model information of the catchment Tulip Garden (Tulipanhave) in Smørum illustrated together with the main trunk rainwater pipe.

200.0 300.0 400.0 500.0 600.0 700.0 800.0 900.0 1000.0 1100.0 1200.0

[m]

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28.0

29.0

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[m]

Link Water Level - 1-1-1994 02:34:50 gan-alt3-T10.PRF

Langtoften

Abildto

ften

Målø

vve

j

Bassin

6014

304

6014

302

6014

300

6014

298

6014

299

6014

290

6014

291n

y

6014

272

6014

270

6014

268

6014

266

6014

264

6014

262

6014

260

6014

158

6014

156

6014

154

6014

152

OV

6014

150

6014

148

6014

146

6012

086

6012

084

6012

082

6012

080

6012

078

6012

076

6012

074

6012

072

6012

070

6012

068

6012

066

6012

064

6012

060

Ground Lev.

Invert lev.

Length

Diameter

Slope o/oo

[m]

[m]

[m]

[m]

36.2

4

35.6

2

36.1

3

36.6

6

36.6

2

36.4

0

36.0

6

36.2

3

36.3

5

36.6

8

36.2

6

35.0

0

33.0

0

32.0

7

31.0

8

32.0

0

32.0

0

31.5

8

32.2

7

32.5

1

32.8

0

32.7

3

31.0

9

30.1

8

30.2

3

32.9

7

32.7

8

32.6

5

32.5

3

32.3

2

32.1

5

31.9

8

31.8

0

31.7

0

31.5

2

31.4

1

31.2

9

31.1

0

30.7

7

29.4

3

29.3

0

29.1

5

29.0

1

28.7

9

28.5

9

28.4

1

28.2

9

28.0

8

27.9

6

27.8

9

48.20 43.99 40.45 47.18 42.92 38.53 38.91 55.99 54.21 67.06 51.15 53.99 52.14 61.49 49.00 50.72 51.64 49.86 45.48 60.24

0.60 0.60 0.60 0.60 0.60 0.60 0.60 0.70 0.70 0.30 0.70 0.50 0.70 0.70 0.70 0.70 0.70 0.70 0.70 0.70 0.80 0.80

3.45 4.36 3.86 4.20 3.81 3.41 4.19 2.86 3.08 2.50 6.09 19.98 2.54 2.78 2.68 3.58 4.08 3.55 2.32 4.21 2.64 1.16

m3/sDischarge 0.069 0.233 0.235 0.236 0.237 0.312 0.312 0.470 0.053 0.053 0.360 0.359 0.359 0.359 0.536 0.536 0.537 0.537 0.578 0.579 0.579

1

2

3 4

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The model was based on calculation level 1, CDS-rain (T=5) from SVK 28. The permeable area was calculated on the basis of 100% roof area of all houses in the catchment added to 90% of the road area in the catchment. The safety factor was equal to 1.44 and based on 1.2 climate safety factor and 1.2 modeling uncertainty. No expectation of expanded permeable area in the future was taken into consideration for the safety factor determination [Envidan, 2007].

A proposal for a solution was delivered to the MWCE by November 2007. A longitudinal profile of the above-mentioned trunk sewer pipe with status calculations is shown in figure 16a and with the solution proposal is shown in figure 16b. The solution has suggested that the pipe mentioned should be replaced with ones of larger dimension, which meant that the solution incurred costs of excavation work and replacement along almost the entire pipe [Envidan, 2007].

a) Longitudinal profile of status model.

b) Longitudinal profile of proposed solution model.

Figure 16: Two longitudinal profiles of the trunk sewer in Tulipanhave (Tulip Garden) catchment in Smørum. Profile a shows the status model with 3 locations of flooding along the profile. Profile b shows the proposed solution that delivered to the MWCE still with flooding in one location.

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38.0

39.0

[m]

Link Water Level - 1-1-1994 02:15:23 StatusBase.PRF

06B06

0R

06B05

9R

06B05

8R

06B05

5R

06B05

3R

06B05

0R

06B04

7R

06B04

4R

06B04

1R

06B03

9R

06B03

6R

06B03

4R

06B03

1R

06B02

8R

06B02

6R

06B02

3R

06B02

1R

06B01

9R

06B01

7R

06B01

5R

06B01

3R

06B01

1R

06B00

9R

06B00

7R

06B00

3R

06B00

0R

Ground Lev.

Invert lev.

Length

Diameter

Slope o/oo

[m]

[m]

[m]

[m]

38.7

2

38.4

0

37.1

7

35.7

9

34.6

9

35.1

4

35.3

4

35.0

2

34.0

7

32.9

1

31.4

9

32.6

2

30.2

3

30.9

7

31.5

3

31.8

0

32.0

6

32.3

6

32.1

2

32.6

2

28.2

2

27.4

1

27.1

2

35.1

0

34.7

0

34.1

3

33.3

3

33.0

2

32.6

2

32.4

4

32.1

8

32.0

4

30.7

1

28.9

3

28.7

9

28.6

8

28.6

3

28.4

6

28.2

0

27.9

3

27.5

6

27.0

9

26.9

1

26.8

7

25.9

8

25.4

3

47.25 43.27 44.61 56.42 50.31 67.16 51.04 56.93 50.66 60.97 48.66 59.10 46.68 47.21 53.00 51.16 56.55

0.20 0.20 0.40 0.40 0.40 0.40 0.40 0.50 0.50 0.50 0.50 0.60 0.60 0.60 0.60 0.60 0.60 0.60 0.70 0.70

8.47 13.17 9.99 4.93 3.19 5.17 2.08 26.06 31.26 2.76 1.80 1.03 2.88 5.57 5.72 6.98 9.19 4.98 0.71

m3/sDischarge 0.006 0.048 0.048 0.202 0.202 0.202 0.202 0.231 0.232 0.270 0.320 0.187 0.207 0.464 0.465 0.498 0.505 0.583 0.709

0.0 100.0 200.0 300.0 400.0 500.0 600.0 700.0 800.0 900.0 1000.0 1100.0

[m]

25.0

26.0

27.0

28.0

29.0

30.0

31.0

32.0

33.0

34.0

35.0

36.0

37.0

38.0

39.0

[m]

Link Water Level - 1-1-1994 02:13:15 planBase.PRF

06B06

0R

06B05

9R

06B05

8R

06B05

5R

06B05

3R

06B05

0R

06B04

7R

06B04

4R

06B04

1R

06B03

9R

06B03

6R

06B03

4R

06B03

1R

06B02

8R

06B02

6R

06B02

3R

06B02

1R

06B01

9R

06B01

7R

06B01

5R

06B01

3R

06B01

1R

06B00

9R

06B00

7R

06B00

3R

06B00

0R

Ground Lev.

Invert lev.

Length

Diameter

Slope o/oo

[m]

[m]

[m]

[m]

38.7

2

38.4

0

37.1

7

35.7

9

34.6

9

35.1

4

35.3

4

35.0

2

34.0

7

32.9

1

31.4

9

32.6

2

30.2

3

30.9

7

31.5

3

31.8

0

32.0

6

32.3

6

32.1

2

32.6

2

28.2

2

27.4

1

27.1

2

35.1

0

34.7

0

34.1

3

33.3

3

33.0

2

32.6

2

32.4

4

32.1

8

32.0

4

30.7

1

28.9

3

28.7

9

28.6

8

28.6

3

28.4

6

28.2

0

27.9

3

27.5

6

27.0

9

26.9

1

26.8

7

25.9

8

25.4

3

47.25 43.27 44.61 56.42 50.31 67.16 51.04 56.93 50.66 60.97 48.66 59.10 46.68 47.21 53.00 51.16 56.55

0.20 0.20 0.40 0.50 0.60 0.60 0.60 0.70 0.70 0.70 0.70 0.70 0.70 0.70 0.70 0.70 0.70 0.70 0.70 0.70

8.47 13.17 9.99 4.93 3.19 5.17 2.08 26.06 31.26 2.76 1.80 1.03 2.88 5.57 5.72 6.98 9.19 4.98 0.71

m3/sDischarge 0.003 0.061 0.062 0.235 0.235 0.235 0.235 0.279 0.276 0.314 0.377 0.225 0.254 0.549 0.549 0.586 0.593 0.699 0.860

14 - 18

However the model was received and discussed internally. A priority was set by the MWCE for the carrying out of excavation work to replace pipes that need hydraulic capacity optimization in the same location, where there are physically defective pipes that need to be replaced. The solution model was re-evaluated. The re-evaluation resulted in an alternative solution that is illustrated in figure 17.

Figure 17: An alternative solution for the main rainwater trunk sewer in Tulipanhave (Tulip Garden) catchment, where instead of replacing the whole pipe, detention pipe has been recommended in two places to solve the problem. The solution has also included moving one manhole to a higher level and reducing or throttling the dimension of two pipes.

The alternative solution proposed by the MWCE recommends a partial replacement of the main rainwater trunk sewer pipe in the form of two detention pipes, moving the one manhole to a higher level of terrain, as it is presented in figure 18 and the dimension reduction or throttling of two pipes. This solution means that the excavation work is significantly reduced and the flooding as in figure 16 is eliminated.

The MWCE has decided to calibrate and verify the model. This decision was taken against the background of achieving a model with smaller degree of incertitude. This can result in a solution with more precise economic outcome. Therefore a flow survey program was carried out in summer 2008 and the results are anticipated in fall 2008.

It has also been decided to carry out TV-inspection on especially unclear observations that need to be confirmed such as either pipe settling or sediments that create the appearance of standing water in pipes. This can also have a hydraulic effect. Besides a decision should be made whether excavation should be done or a no-dig renovation is sufficient to restore the system to a functional level.

However until this time a temporary saving of more than 5 million DKK (€ 0.67 million) was achieved by the alternative solution.

0.0 100.0 200.0 300.0 400.0 500.0 600.0 700.0 800.0 900.0 1000.0

[m]

25.0

26.0

27.0

28.0

29.0

30.0

31.0

32.0

33.0

34.0

35.0

36.0

37.0

38.0

39.0

[m]

Link Water Level - 1-1-1994 02:14:17 StatusBase.PRF

06B06

0R

06B05

9R

06B05

8R

06B05

5R

06B05

3R

06B05

0R

06B04

7R

06B04

4R

06B04

1R

06B03

9R

06B03

6R

06B03

4R

06B03

1R

06B02

8R

06B02

6R

06B02

3R

06B02

1R

06B01

9R

06B01

7R

06B01

5R

06B01

3R

06B01

1R

06B00

9R

06B00

7R

06B00

3R

06B00

0R

Ground Lev.

Invert lev.

Length

Diameter

Slope o/oo

[m]

[m]

[m]

[m]

38.7

2

38.4

0

37.1

7

35.7

9

34.6

9

35.1

4

35.3

4

35.0

2

34.0

7

32.9

1

31.4

9

32.6

2

31.5

0

30.9

7

31.5

3

31.8

0

32.0

6

32.3

6

32.1

2

32.6

2

28.2

2

27.4

1

27.2

2

35.1

0

34.7

0

34.1

3

33.3

3

33.0

2

32.6

2

32.4

4

32.1

8

32.0

4

30.7

1

28.9

3

28.7

9

28.7

1

28.6

3

28.4

6

28.2

0

27.9

3

27.5

6

27.0

9

26.9

1

26.8

7

25.9

8

25.5

8

47.25 43.27 44.61 56.42 50.31 67.16 51.04 56.93 50.66 40.90 42.09 59.10 46.68 47.21 53.00 51.16 36.12 56.55

0.20 0.20 0.25 0.20 1.00 1.00 0.40 0.50 0.50 0.50 0.50 0.60 1.25 1.25 1.50 1.50 0.60 0.60 0.70 0.70

8.47 13.17 9.99 4.93 3.19 5.17 2.08 26.06 31.26 2.76 1.96 1.90 2.88 5.57 5.72 6.98 9.19 4.98 0.71

m3/sDischarge 0.005 0.058 0.060 0.220 0.203 0.193 0.192 0.230 0.232 0.263 0.313 0.284 0.249 0.466 0.432 0.464 0.470 0.563 0.706

Manhole moved

Manholes removed

Detention pipe

Reduction of dimension or

throttling

15 - 18

Figure 18: A description of the achievement of a higher terrain level by moving a manhole on the rainwater main trunk sewer in Tulipanhave (Tulip Garden) catchment to a higher ground level in order to avoid flooding.

Assessment

The hydraulic modeling in the past four years has optimized the decision-making process towards focused decisions in the direction of qualitative and economically sustainable projects. The following was achieved in renovation and development projects:

1. Quality control of the rational method hydraulic design by modeling, which gave a better overall hydraulic evaluation of the development and renovation projects.

2. Hydraulic capacity of the drainage system compatible with the service level and requirement of the guidelines of SVK 27 in both renovation and development projects.

3. Reordering of the priority of renovation projects towards economically sustainable solutions on the basis of hydraulic evaluation.

4. Large savings by implementing hydraulic modeling.

G. level: 30.23

G. level: 31.50

16 - 18

Decisions

On the basis of the experience with hydraulic modeling by implementing MIKE URBAN-MOUSE in drainage projects, the MWCE has taken a decision to implement hydraulic modeling using one dimensional (1-D) modeling of MIKE URBAN-MOUSE and two dimensional (2-D) modeling of MIKE FLOOD as a support tool to establish and develop long term strategic plans, short term strategic plans and detailed plans for renovation and development projects. A decision was taken to either build up models and/or externally order models based on the following lines:

1. Calculation level 2, CDS from SVK 28 and CDS of local rain gauges.

2. Calculation level 2, historical rain from representative rain stations in SVK 28 and from local rain gauges.

3. Calculation level 3, by carrying out a flow survey program to verify and calibrate the model.

4. Testing the pipe systems with CDS and then historical rain.

5. Testing detention systems (tanks, basins, lagoons, lakes and detention pipes) with historical rain.

6. Testing the stability of the model under different historical rain series.

7. Using a safety factor equal to 1.45 in future scenarios for verified models. This factor consists of climate change factor equal to 1.2, condensation factor equal to 1.1 and model uncertainty factor equal to 1.1. For unverified models a total safety factor equal to 1.6 is used, which includes a model uncertainty factor equal to 1.2 [SVK 27, 2005].

8. However, SVK 29 has suggested a climate safety factor equal to respectively 1.2, 1.3 and 1.4 for 2, 10 and 100 years’ scenario or lifetime [SVK 29, 2008]. This is currently a matter for internal discussion.

9. In the case of an unverified model, determined reduction factors equal to 1.0 for roofs, 0.1 for green areas and 0.9 for roads to be implemented in modeling.

10. Using the land register map as catchments boundary basis with initial concentration time equal to 4 minutes. When larger catchments are used, a standard initial concentration time equal to 7 minutes is used.

11. New catchment borders, discharge values, permeability percentage to be calculated with a view to implementation in strategic planning.

12. Establishing local key values for time-area parameters of modeling in Egedal regarding concentration time, impermeability percentage of classified types of catchments, discharge values of different types of catchments and infiltration to the drainage system.

Long term plans

On the basis of the achieved results in hydraulic modeling using MIKE URBAN-MOUSE the following procedures have been adopted in the MWCE:

1. Gradual connection of all models of MIKE URABN-MOUSE together to attain better overview regarding flooding and hydraulic difficulties in the system. A terrain model and MIKE FLOOD will be implemented to further optimize this task.

17 - 18

2. Creation of scenarios for extreme situations to predict and handle flooding in such scenarios.

3. The initiation of a basis of effective management and operation of the drainage system under extreme weather events based on results from hydraulic modeling.

4. Implementation of modeling to establish a foundation for emergency plans.

5. Establishing a network of local rain gauges, flow survey programs and online data to implement in models verification and calibration.

6. Taking a next step, which is two dimensional (2-D) hydraulic modeling implementing MIKE FLOOD in order to obtain as credible scenarios as possible that can achieve integration with other hydraulic bodies, such as streams, rivers, lakes and farm-draining systems.

7. The initiation of and/or the participation in radar and early warning system implementation to prepare the drainage system in extreme weather in order to minimize or avoid damage by flooding. Besides forecast radar system can be implemented for collecting rain data, support emergency procedures and updating calculations of MIKE URBAN-MOUSE.

Conclusions

After 4 years of hydraulic modeling implementing MIKE URBAN-MOUSE in the projects of the MWCE, the following can be concluded in regard to hydraulic modeling:

1. It is an effective tool to ensure a quality of drainage system projects that lives up to guideline requirements of SVK 27, SVK 28 and SVK 29.

2. It is a successful support in reducing project costs and carrying out economically sustainable projects. In total more than 6.3 million DKK (€ 0.84 million) were saved in 2007.

3. It is a means to handle the challenge of climate change and imminent higher level of intensity in future storms, which helps a sustainable economic investment.

4. However, building up expertise and know-how within the MWCE in modeling is an assignment that needs a thorough plan. This includes tasks supporting modeling such as updating the databases of the pipe system registration, surveying, flow survey programs, rain gauges and online data.

5. To expand the frontiers of implementing hydraulic modeling in areas of analysis, control and overall planning beyond current implementation of modeling in specific projects in the MWCE, modeling should be presented to the organization as a modern support aid for decision-making processes rather than a complicated high-tech tool. This requires facilitating the use of modeling, training specialist personnel on it and presenting transparent results to support decision-making. This support must always be available during the process of reaching decisions.

18 - 18

References

[Al-Shididi, 2006]: Al-Shididi, Sabah (5 October 2006); Afhjælpning af oversvømmelse i Ganløse under kraftige regnhændelser, presentation at public meeting in Stenløse city hall, Stenløse, Denmark.

[Al-Shididi, 2008]: Al-Shididi, Sabah (2 April 2008); MIKE URBAN and MOUSE – Anvendelse i kommuneregi; Presentaion at the DHI’s MIKE software users’ seminar in Rungstedgaard, Denmark.

[Al-Shididi, 2008a]: Al-Shiddi, Sabah (30 January 2008); Oversvømmelse i Egedal Kommune i sommer 2007 – Analyse og løsningsforslag til afløbssystemet, Presentation at the Center for the Environment, Ølstykke city hall, Egedal, Denmark.

[DS 432, 1994]; Norm for afløbsinstallationer, Ingeniørforening i Danmark, 2. udgave.

[Envidan, 2007]; Kloaksaneringsplan – Egedal Kommune, Smørumnedre by (October 2007), report, EnviDan, Denmark.

[Stenløse, 2004]; Stenløse Kommune (June 2006); Tillæg nr. 1 til spildevandsplan 2001-2012 – Kloakering af Stenløse Syd, Stenløse Kommune.

[Stenløse, 2006]; Stenløse Kommune (februar 2006), Tillæg nr. 2 til spildevandsplan 2001-2012 – Kloakering af GA14 i Ganløse, Stenløse Kommune.

[SVK 16, 1974]: Bestemmelser af regnrækker, Skrift nr. 16; DIF Spildevandskomiteen; ISBN 87-571-0477-8.

[SVK 27, 2005]: Funktionspraksis for afløbssystemer under regn (October 2005), Skrift nr. 27, IDA spildevandskomiteen.

[SVK 28, 2006]: Regional variation af ekstremregn i Danmark – ny bearbejdning (1979 - 2005), (October 2006), Skrift nr. 28, IDA Spildevandskomiteen.

[SVK 29, 2008]: Forventede ændringer i ekstremregn som følge af klimaændringer (August 2008), IDA Spildevandskomiteen.

[Winther, et.al., 2006]: Winther, Life; Linde, Jens Jørgen; Jensen, H. Thorkild; Mathiasen, Leo Lund; Johansen, Niels Bent (2006); Alføbsteknik, 5th edition, Polyteknik Forlag, ISBN 87-502-0975-2.