Ms. Petra Deproost, Government of Flanders, Belgium. Global Symposium on Soil Erosion (GSER19), 15 - 17 May 2019 at FAO HQ.

1. Modelling soil erosion and
sediment transport in Flanders
Petra Deproost – Government of
Flanders
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2. Need for more insight in soil erosion and
sediment transport processes in Flanders
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• Soil erosion in the Flemish loess belt causes
• loss of soil quality
• mud streams in urban areas
• high sediment loads in rivers and sewage systems
• Priority areas for actions ? Impact of erosion control measures?
=> Modified version WaTEM/SEDEM (KULeuven)
• Updated input data, algorithms and parameter choices
• Recalibration based on an extended dataset of sediment loads

3. Annual soil loss (A)
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𝐴 = 𝑅. 𝐾. 𝐿𝑆. 𝐶. 𝑃 (RUSLE)
• R : rain erosivity factor => 1250 MJ.mm.ha-1.h-1.year-1
• Royal Meteorological Institute (Ukkel, Brussels), 1988-2017
• 43 meteorological stations, 2001-2017
(methodology: Verstraeten et al. 2006)

4. Annual soil loss (A)
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𝐴 = 𝑅. 𝐾. 𝐿𝑆. 𝐶. 𝑃 (RUSLE)
• K : soil erodibility factor => soil texture
• LS : topographical factor
• 2-dimensional flux decomposition algorithm
• high resolution DTM based on LIDAR elevation data
(16 points/m²) => 20 meter resolution grid
• roads, parcel borders and land use are taken into
account
• C : crop management factor
• arable land: 0,37
• grassland: 0,01
• forest: 0,001
• P : erosion control practice factor => 1

5. Transport capacity (TC)
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𝑇𝐶 = 𝑘𝑇𝐶. 𝑅. 𝐾. (𝐿𝑆 − 4,12. 𝑆0,8)
• kTC : transport capacity coefficient => determined by
calibration (26 catchment in Flanders)
• kTC high : arable land => 12
• kTC low : grassland, forest => 3
Model Efficiency = 0,70

6. Erosion and sedimentation processes
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• Routing algorithm => sediment pathway
• SedimentIN + gross erosion < TC
• net erosion = gross erosion
• SedimentIN + gross erosion > TC
• net erosion < gross erosion
• if sedimentIN > TC: net sedimentation
(Verstraeten et al. 2007)

7. Sediment transport through the landscape
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• Sediment flows on the land
• Sediment delivery to rivers
• Identification of source
subcatchments

8. Impact of soil erosion control measures
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Catchment: 830 ha

9. Impact of soil erosion control measures
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Erosion control measures Amount Erosion Sediment delivery
to river
Grass buffer strips 48 ha -15% -18%
Erosion control measures Amount Erosion Sediment delivery
to river
Riperian filter strips 8 ha neglegible -25%
Buffer basins 2 neglegible -17%
Reduced tillage 388 ha -47% -23%
Maximal scenario -47% -56%
• Additional measures
• Current measures

10. Remarks and future improvements
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• Insertion of missing data with major impact on sediment
transport and sediment delivery to waterways
• small ditches
• sewage system
• Refinement of the impact of erosion control measures
• C-factor calculations
• buffering measures
• Increase of model resolution
• 20 meter resolution => 5 meter resolution

11. Conclusions
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• WaTEM/SEDEM is used in Flanders as an operational tool to
• calculate and visualize erosion and sediment transport at different
scales
• determine priority areas for area-oriented actions
• evaluate the impact of current or future land use choices,
agricultural practices and erosion control measures
• Model results support local actors to choose, prioritize and
promote measures on the basis of their effectiveness
• The model can be applied to calculate erosion or sediment
delivery indicators to evaluate soil protection policies