GRASS GIS: r.sim.sediment

NAME

r.sim.sediment - Sediment transport and erosion/deposition simulation using path sampling method (SIMWE)

KEYWORDS

raster, sediment flow, erosion, deposition

SYNOPSIS

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

Flags:

--overwrite: Allow output files to overwrite existing files
--verbose: Verbose module output
--quiet: Quiet module output

Parameters:

elevin=name: Name of the elevation raster map [m]
wdepth=name: Name of the water depth raster map [m]
dxin=name: Name of the x-derivatives raster map [m/m]
dyin=name: Name of the y-derivatives raster map [m/m]
detin=name: Name of the detachment capacity coefficient raster map [s/m]
tranin=name: Name of the transport capacity coefficient raster map [s]
tauin=name: Name of the critical shear stress raster map [Pa]
manin=name: Name of the Mannings n raster map
maninval=float: Name of the Mannings n value; Default: 0.1
vector=name: Name of the sampling locations vector points map
tc=name: Output transport capacity raster map [kg/ms]
et=name: Output transp.limited erosion-deposition raster map [kg/m2s]
conc=name: Output sediment concentration raster map [particle/m3]
flux=name: Output sediment flux raster map [kg/ms]
erdep=name: Output erosion-deposition raster map [kg/m2s]
nwalk=integer: Number of walkers
niter=integer: Time used for iterations [minutes]; Default: 10
outiter=integer: Time interval for creating output maps [minutes]; Default: 2
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 [m]), flow gradient given by the first-order partial derivatives of elevation field ( dxin and dyin), overland flow water depth ( wdepth [m]), detachment capacity coefficient (detin [s/m]), transport capacity coefficient (tranin [s]), critical shear stress (tauin [Pa]) 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 from feet to metric system using database/projection information, so the elevation always should be in meters. 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]i that are output almost immediately and can be viewed while the simulation continues. Sediment flow rate raster map flux [kg/ms], and net erosion/deposition raster map [kg/m²s] can take longer time depending on time step and simulation time. Simulation time is controled by niter [minutes] parameter. If the resulting erosion/deposition map is noisy, higher number of walkers, given by nwalk should be used.

NOTES

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., Proceedings of the XVth International Conference on Computational Methods in Water Resources (CMWR XV), June 13-17 2004, Chapel Hill, NC, USA, Elsevier, pp. 1479-1490.

Mitasova H, Mitas, L., 2000, Modeling spatial processes in multiscale framework: exploring duality between particles and fields, plenary talk at GIScience2000 conference, Savannah, GA.

Mitas, L., and Mitasova, H., 1998, Distributed soil erosion simulation for effective erosion prevention. Water Resources Research, 34(3), 505-516.

Mitasova, H., Mitas, L., 2001, Multiscale soil erosion simulations for land use management, In: Landscape erosion and landscape evolution modeling, Harmon R. and Doe W. eds., Kluwer Academic/Plenum Publishers, pp. 321-347.

Neteler, M. and Mitasova, H., 2008, Open Source GIS: A GRASS GIS Approach. Third Edition. The International Series in Engineering and Computer Science: Volume 773. Springer New York Inc, p. 406.

Last changed: $Date: 2008-02-22 21:58:58 -0800 (Fri, 22 Feb 2008) $

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