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A spatial information technology approach for the
mapping and quantification of gully erosion
University of Lleida, Spain
José A. Martínez-Casasnovas
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Content
1. Introduction.– Spatial information technologies for gully erosion
analysis.– The gully erosion problem in the study area.– Objectives.
2. Materials and methods.
3. Results.
4. Conclusions.
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1. Introduction
• A lot of research works on Gully Erosion Mapping have been based on Remote Sensing techniques, and particularly on airphoto interpretation.
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• Satellite images may also offer interesting possibilities provided that gullies affect areas wide enough to be covered by the resolution of the images.
Landsat 5 TM Image Walls Activity Map
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• At detailed scale, Photogrammetry has also been used to map the volumetric changes in gullies, sediment production and gully erosion rates.
1957
1993
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The convergenceand extension ofPhotogrammetry,Digital Imaging Technologyand GIS have contributed to the use of multi-temporal DEM to computesedimemt production by gully erosion.
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• In this context, the present work shows the methods and results of a research to compute Gully Erosion Rates using Spatial Information Technologies:
The Channel Incision Rate
The Sediment Production Rate
The Gully Walls Retreat Rate
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España
Cataluña
Penedès– Suffers serious gully erosion problems– Gully erosion is favoured by the cropping of vineyards
The research was carried out in thePENEDÈS Vineyard Region (NE Spain)
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Contouring and terracing
1957
1957
Elimination of traditional conservation measures
1993
• Particularly important has been the period after the advent of mechanization (1950’s).
1993
• The area has suffered a substantial transformation.
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• At present, the problems are so grave that even afect to urban areas, that were built-up in the neighbour of gullies.
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Alt Penedès Rierussa Catchment
25 km2
Martorell
Piera
Sant Sadurníd’Anoia
Sierra
Pre
litora
l
Sierr
a Lito
ral
Study Area
SpainCatalonia
LithologyMARLS, Sandstones, Conglomerates
Rainfall471 - 670 mm/yearAutumn & Spring> 100 mm h-1 in short periods
L’Anoia
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2. Materials and methods
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1957 Situation 1993 Situation
Aerial Photographs1957, 1:30000
Aerial Photographs1986, 1:30000
Orthophoto 1993
DEM
Gullied area 1957 DEM Gullied area 1993
Changes:Retreat of gully walls
Changes: Channel Incision & Sediment Production
Gully Walls Retreat / Channel Incision / Sediment Production
Photo-interpretation Restitution Photo-interpretationGeo-referenciation
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Construction of the 1957 DEMPhotogrammetric Restitution of Contours (10 m interval)
Filtering Spatial Interpolation
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Sediment Production Rate (SPR)
1993 DEM 1957 DEM
-
GR2 x ED x Bd
A x TSPR =
Bulk density(1.735 Mg m-3)
Time of the studied period (years)Surface of the gullied area (ha)
Grid resolution (m)
Elevation differences (ED)
=
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3. Results
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1. Gully area extent and Rate of gully walls retreat
Overlaying (UNION) of Gully Area Extent Maps
Overlay
1957
1993
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Contingence matrix: UNION of Gully Areas
Year 1993 (ha)
Gullied areas
Non-gullied areas
565
1770
Year 1957 (ha)
Gullied areas Non-gullied areas
Areas without changes
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Year 1993 (ha)
Gullied areas 77
Non-gullied areas
565
1770
Year 1957 (ha)
Gullied areas Non-gullied areas
Contingence matrix: UNION of Gully Areas
1957 1993
Gully Retreat
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Year 1993 (ha)
Gullied areas 77
Non-gullied areas 39
565
1770
Year 1957 (ha)
Gullied areas Non-gullied areas
New parcel
1957 1993
Contingence matrix: UNION of Gully Areas
Gully Filling
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Year 1993 (ha)
Gullied areas 77 642
Non-gullied areas 39
565
1770 1809
Total (Year 1957) 604 1848 2451
Year 1957 (ha)
Gullied areas Non-gullied areas Total (Year 1993)
Contingence matrix: UNION of Gully Areas
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Retreat rate
(Rierusa Catchment)
2.1 ha year-1
Gully Retreat Rate
Linear Retreat Rate 0.2 m year-1
Retreat rate
(m2 / 1000 m2 of catchment)
0.9 ‰ year-1
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When did the acceleration of gully erosion processes start ?
1957 1993
77 ha in 36 years
Let’s apply back this rate considering that
at present there are ~ 640 ha of gullies
~ 1650
From XVI century = Massive plantation of Vineyards under theprotection of temporary contracts till the end of vineyards’ life.(Balcells 1980)
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Altitude difference (m)(1993 - 1957)
Areas withloss of materials
Areas withgain of materials
2. Channel Incision and Sediment Production Rates
0.8 m year-1
0.15 - 0.35 m year-1
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2. Channel Incision and Sediment Production Rates
Topographic changes 1957-1993 - Profile 1
0.0
50.0
100.0
150.0
200.0
250.0
0 25 50 75 100125150175200225250275300325350375400425
Distance (m)
Alt
itu
de
(m
)
-30.0
-25.0
-20.0
-15.0
-10.0
-5.0
0.0
5.0
10.0
Alt
itu
de
dif
fere
nc
es
(m
)
1957 1993 Difference
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Sediment Production Rate
Rate in the Gully-eroded Areas
1322 +/- 142 Mg ha-1 year-1
Rate with respect the
total catchment area
331 +/- 35 Mg ha-1 year-1
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Comparison with respect other research areas
SE France (Bufalo and Nahon 1992)
190 Mg ha-1 year-1
Barasona basin (NE Spain)(Penella 1997)
375 Mg ha-1 year-1
Only account foroverland flow
erosion processes
Mass Movements
Penedès, Spain
1322 Mg ha-1 year-1
Channel Incision
Overland flowNew Zealand
(DeRose et al. 1998)
1550 - 2480 Mg ha-1 year-1
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4. Conclusions
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• The present work confirms the conclusions of other researchers who state that sediment production by gully erosion is very far from negligible
(around 1.300 Mg ha-1 year-1 are a lot of tons).
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• In comparison with other methods of measuring sediment production, the proposed method computes a rate that is one order of magnitude higher.
Mass Movements
Channel Incision
Overland flow
• The reason is that it integrates the losses due to:
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• In the Penedès region, the research confirmed the acceleration of erosion since the late Middle Ages because of the massive deforestation and plantation of vineyards, and in the recent past since the advent of mechanization.
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• At present, we are working on a multi-temporal study centered at the head of the gully system, using 1:5.000 aerial photographs.
• This will serve to compute gully erosion rates at very detailed scale from high resolution DEMs.