
NAME
r.sim.sediment
DESCRIPTION
r.sim.sediment is a landscape scale, simulation
model of soil erosion, sediment transport and deposition caused by flowing
water designed for spatially variable terrain, soil, cover and
rainfall excess conditions. The soil erosion model is based on the theory
used in the USDA WEPP hillslope erosion model, but it has been generalized
to 2D flow. The solution is based on the concept of duality between fields and
particles and the underlying equations are solved by Green's
function Monte Carlo method, to provide robustness necessary for
spatially variable conditions and high resolutions (Mitas and Mitasova
1998). Key inputs of the model include the following raster files:
elevation ( elevin), flow gradient given by the first-order partial
derivatives of elevation field ( dxin and dyin),
overland flow water depth ( wdepth), detachment capacity coefficient (detin),
transport capacity coefficient (tranin), critical shear stress (tauin)
and surface roughness coefficient called Manning's n (manin raster file).
Partial derivatives can be computed by v.surf.rst
or r.slope.aspect
module. The data are automatically converted data from feet to metric
system using database/projection information. The water depth file can be
computed using r.sim.water
module. Other parameters must be determined using field measurements or
reference literature (see suggested values in Notes and References).
Output includes transport capacity raster file tc in [kg/ms],
transport capacity limited erosion/deposition raster file
et [kg/m2s], sediment flow rate raster file
flux [kg/ms], and net erosion/deposition raster file [kg/m2s].
Simulation time is controled by niter parameter. The default value is 1000,
depending on complexity of terrain, land cover and size of the area, several thousand
iterations may be needed to reach the steady state. Output
files can be saved during simulation using outiter parameter
defining simulation time step for writing output files. This option requires
time series flag -t. Files are saved with suffix containing
iteration number (e.g. name.500, name.1000, etc.).
NOTES
SEE ALSO
v.surf.rst,
r.slope.aspect,
r.sim.water
AUTHORS
Helena Mitasova, Lubos Mitas
North Carolina State University
hmitaso@unity.ncsu.edu
Jaroslav Hofierka
GeoModel, s.r.o. Bratislava, Slovakia
hofierka@geomodel.sk
Chris Thaxton
North Carolina State University
csthaxto@unity.ncsu.edu
csthaxto@unity.ncsu.edu
REFERENCES
Mitasova, H., Thaxton, C., Hofierka, J., McLaughlin, R., Moore, A., Mitas L., 2004,
Path sampling method for modeling overland water flow, sediment transport
and short term terrain evolution in Open Source GIS.
In: C.T. Miller, M.W. Farthing, V.G. Gray, G.F. Pinder eds.,
Computational Methods in Water Resources, Elsevier.
Mitas, L., and Mitasova, H., 1998, Distributed soil erosion
simulation for effective erosion prevention. Water Resources Research,
34(3), 505-516.
Neteler, M. and Mitasova, H., 2004, Open Source GIS: A GRASS GIS Approach, Second Edition,
Kluwer International Series in Engineering and Computer Science, 773, Kluwer Academic Press / Springer,
Boston, Dordrecht, 424 pages.
Last changed: $Date: 2006/11/18 09:58:59 $
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