Processbased simulation of erosion and deposition in a GIS:

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Process-based simulation of erosion and
deposition in a GIS
A laboratory for modeling human impacts on a
landscape
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Modeling environment built in GRASS GIS

• USPED equation (calculated at each cell)
• Unit Stream Power Erosion/ Deposition
• ED d(T ? dx ? cos a) d(T ? dy ? sin a)
• ED is net erosion or deposition of sediment
• a is the topographic aspect
• dx and dy are the sediment transport capacity
  in x and y directions for a given surface process
  (see next slide)
• T (sediment transport) is the RUSLE equation
  value (see next slide)

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• DX and DY for sheetwash (overland flow)
• dx f ? r ? sin(slope)
• dy f ? r ? cos(slope)
• where
• f is the flow accumulation or flux (number of
  cells that drain through each cell)
• r is the resolution of the DEM (dimension of
  the cells)
• RUSLE (Revised Universal Soil Loss Equation)
• T R ? K ? LS ? C ? P
• where
• R is the rainfall intensity factor
• K is the soil erosion resistance factor
• LS is the slope length and steepness factor (in
  USPED, LS is represented by dx and dy)
• C is the vegetation erosion protection factor
• P is the prevention practices factor

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Results for a ten year simulation
Erosion/ Deposition Potential
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Results for a ten year simulation
Terrain Evolution
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Where to next?

• Add soil production (will allow production
  limited function and will prevent excessive
  unrealistic erosion/deposition)
• Differentiate surface processes (ie. have rill
  flow in gullies, sheetwash on slopes, mass
  wasting where appropriate)
• Remove edge effects (shrinking extents)
• Empirical field checking (are the models
  erosion/deposition rates reasonable?)