r.sim.sediment(1grass) GRASS GIS User's Manual r.sim.sediment(1grass)
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 de-
tachment_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 parti-
cles 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 el-
evation field ( dx and dy), overland flow water depth (water_depth
[m]), detachment capacity coefficient (detachment_coeff [s/m]), trans-
port 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 el-
evation always should be in meters. The water depth file can be com-
puted using r.sim.water module. Other parameters must be determined us-
ing 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] parame-
ter. 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., Mi-
tas 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., Proceed-
ings of the XVth International Conference on Computational Methods in
Water Resources (CMWR XV), June 13-17 2004, Chapel Hill, NC, USA, Else-
vier, 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 mod-
eling, 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 Ap-
proach. 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)
Accessed: unknown
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