Provided by: grass-doc_7.8.2-1build3_all 
NAME
r.sim.sediment - Sediment transport and erosion/deposition simulation using path sampling method
(SIMWE).
KEYWORDS
raster, hydrology, soil, sediment flow, erosion, deposition, model
SYNOPSIS
r.sim.sediment
r.sim.sediment --help
r.sim.sediment [-s] elevation=name water_depth=name dx=name dy=name detachment_coeff=name
transport_coeff=name shear_stress=name [man=name] [man_value=float] [observation=name]
[transport_capacity=name] [tlimit_erosion_deposition=name] [sediment_concentration=name]
[sediment_flux=name] [erosion_deposition=name] [logfile=name] [walkers_output=name]
[nwalkers=integer] [niterations=integer] [output_step=integer] [diffusion_coeff=float]
[random_seed=integer] [nprocs=integer] [--overwrite] [--help] [--verbose] [--quiet] [--ui]
Flags:
-s
Generate random seed
Automatically generates random seed for random number generator (use when you don’t want to provide
the seed option)
--overwrite
Allow output files to overwrite existing files
--help
Print usage summary
--verbose
Verbose module output
--quiet
Quiet module output
--ui
Force launching GUI dialog
Parameters:
elevation=name [required]
Name of input elevation raster map
water_depth=name [required]
Name of water depth raster map [m]
dx=name [required]
Name of x-derivatives raster map [m/m]
dy=name [required]
Name of y-derivatives raster map [m/m]
detachment_coeff=name [required]
Name of detachment capacity coefficient raster map [s/m]
transport_coeff=name [required]
Name of transport capacity coefficient raster map [s]
shear_stress=name [required]
Name of critical shear stress raster map [Pa]
man=name
Name of Manning’s n raster map
man_value=float
Manning’s n unique value
Default: 0.1
observation=name
Name of sampling locations vector points map
Or data source for direct OGR access
transport_capacity=name
Name for output transport capacity raster map [kg/ms]
tlimit_erosion_deposition=name
Name for output transport limited erosion-deposition raster map [kg/m2s]
sediment_concentration=name
Name for output sediment concentration raster map [particle/m3]
sediment_flux=name
Name for output sediment flux raster map [kg/ms]
erosion_deposition=name
Name for output erosion-deposition raster map [kg/m2s]
logfile=name
Name for sampling points output text file. For each observation vector point the time series of
sediment transport is stored.
walkers_output=name
Base name of the output walkers vector points map
nwalkers=integer
Number of walkers
niterations=integer
Time used for iterations [minutes]
Default: 10
output_step=integer
Time interval for creating output maps [minutes]
Default: 2
diffusion_coeff=float
Water diffusion constant
Default: 0.8
random_seed=integer
Seed for random number generator
The same seed can be used to obtain same results or random seed can be generated by other means.
nprocs=integer
Number of threads which will be used for parallel compute
Default: 1
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 (elevation [m]), flow gradient given
by the first-order partial derivatives of elevation field ( dx and dy), overland flow water depth
(water_depth [m]), detachment capacity coefficient (detachment_coeff [s/m]), transport capacity
coefficient (transport_coeff [s]), critical shear stress (shear_stress [Pa]) and surface roughness
coefficient called Manning’s n (man 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 transport_capacity in [kg/ms], transport capacity limited
erosion/deposition raster map tlimit_erosion_deposition [kg/m2s]i that are output almost immediately and
can be viewed while the simulation continues. Sediment flow rate raster map sediment_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 controlled by niterations [minutes] parameter. If the resulting
erosion/deposition map is noisy, higher number of walkers, given by nwalkers should be used.
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., 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.
SOURCE CODE
Available at: r.sim.sediment source code (history)
Main index | Raster index | Topics index | Keywords index | Graphical index | Full index
© 2003-2019 GRASS Development Team, GRASS GIS 7.8.2 Reference Manual