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]     [tc=name]     [et=name]    [conc=name]
       [flux=name]     [erdep=name]     [nwalk=integer]     [niter=integer]     [outiter=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

       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

       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

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.

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

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