GRASS GIS: r.sim.sediment

NAME

r.sim.sediment - Overland flow hydrologic model based on duality particle-field concept (SIMWE)

KEYWORDS

raster

SYNOPSIS

r.sim.sediment
r.sim.sediment help
r.sim.sediment [-mt] elevin=string wdepth=string dxin=string dyin=string detin=string tranin=string tauin=string manin=string [vector=string] [tc=string] [et=string] [conc=string] [flux=string] [erdep=string] [nwalk=integer] [niter=integer] [outiter=integer] [density=integer] [diffc=float] [--overwrite] [--verbose] [--quiet]

Flags:

-m: Multiscale simulation
-t: Time-series (dynamic) output
--overwrite: Allow output files to overwrite existing files
--verbose: Verbose module output
--quiet: Quiet module output

Parameters:

elevin=string: Name of the elevation raster map
wdepth=string: Name of the water height raster map
dxin=string: Name of the x-derivatives raster map
dyin=string: Name of the y-derivatives raster map
detin=string: Name of the detachment capacity coefficient raster map
tranin=string: Name of the transport capacity coefficient raster map
tauin=string: Name of the critical shear stress raster map
manin=string: Name of the Mannings n raster map
vector=string: Name of the vector points map with x,y locations
tc=string: Output transport capacity raster map
et=string: Output transp.limited erosion-deposition raster map
conc=string: Output sediment concentration raster map
flux=string: Output sediment flux raster map
erdep=string: Output erosion-deposition raster map
nwalk=integer: Number of walkers; Default: 2000000
niter=integer: Number of time iterations (sec.); Default: 1200
outiter=integer: Time step for saving output maps (sec.); Default: 300
density=integer: Density of output walkers; Default: 200
diffc=float: Water diffusion constant; Default: 0.8

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 maps: 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 map). 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 map tc in [kg/ms], transport capacity limited erosion/deposition raster map et [kg/m²s], sediment flow rate raster map flux [kg/ms], and net erosion/deposition raster map [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

AUTHORS

Helena Mitasova, Lubos Mitas
North Carolina State University
[email protected]

Jaroslav Hofierka
GeoModel, s.r.o. Bratislava, Slovakia

[email protected]

Chris Thaxton
North Carolina State University
[email protected]

[email protected]

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: 2008-01-27 06:04:24 -0800 (Sun, 27 Jan 2008) $

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