r.sim.terrain - GRASS GIS manual

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NAME

r.sim.terrain - Dynamic landscape evolution model

KEYWORDS

raster, terrain, landscape, evolution

SYNOPSIS

r.sim.terrain

r.sim.terrain --help

r.sim.terrain [-f] elevation=name runs=string mode=string [rain_intensity=integer] [rain_duration=integer] [precipitation=name] [k_factor=name] [k_factor_value=float] [c_factor=name] [c_factor_value=float] [m=float] [n=float] [walkers=integer] [runoff=name] [runoff_value=float] [mannings=name] [mannings_value=float] [detachment=name] [detachment_value=float] [transport=name] [transport_value=float] [shearstress=name] [shearstress_value=float] [density=name] [density_value=float] [mass=name] [mass_value=float] [grav_diffusion=float] [erdepmin=float] [erdepmax=float] start=string rain_interval=integer temporaltype=name [threads=integer] elevation_timeseries=name [depth_timeseries=name] [erdep_timeseries=name] [flux_timeseries=name] [difference_timeseries=name] [--overwrite] [--help] [--verbose] [--quiet] [--ui]

Flags:

-f: Fill depressions
--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
runs=string [required]: Run for a single rainfall event or a series of events; Options: event, series; Default: event; event: single rainfall event; series: series of rainfall events
mode=string [required]: SIMWE erosion deposition, USPED transport limited, or RUSLE 3D detachment limited mode; Options: simwe_mode, usped_mode, rusle_mode; Default: simwe_mode; simwe_mode: SIMWE erosion deposition mode; usped_mode: USPED transport limited mode; rusle_mode: RUSLE 3D detachment limited mode
rain_intensity=integer: Rainfall intensity in mm/hr; Default: 50
rain_duration=integer: Total duration of storm event in minutes; Default: 60
precipitation=name: Precipitation file; Name of input precipitation file
k_factor=name: K factor; Soil erodibility factor
k_factor_value=float: K factor constant; Soil erodibility constant; Default: 0.25
c_factor=name: C factor; Land cover factor
c_factor_value=float: C factor constant; Land cover constant; Default: 0.1
m=float: Water flow exponent; Water flow exponent; Default: 1.5
n=float: Slope exponent; Slope exponent; Default: 1.2
walkers=integer: Number of walkers (max = 7000000); Default: 1000000
runoff=name: Runoff coefficient; Runoff coefficient (0.6 for bare earth, 0.35 for grass or crops, 0.5 for shrubs and trees, 0.25 for forest, 0.95 for roads)
runoff_value=float: Runoff coefficient; Runoff coefficient (0.6 for bare earth, 0.35 for grass or crops, 0.5 for shrubs and trees, 0.25 for forest, 0.95 for roads); Default: 0.35
mannings=name: Manning's roughness coefficient; Manning's roughness coefficient
mannings_value=float: Manning's roughness coefficient; Manning's roughness coefficient; Default: 0.04
detachment=name: Detachment coefficient; Detachment coefficient
detachment_value=float: Detachment coefficient; Detachment coefficient; Default: 0.01
transport=name: Transport coefficient; Transport coefficient
transport_value=float: Transport coefficient; Transport coefficient; Default: 0.01
shearstress=name: Shear stress coefficient; Shear stress coefficient
shearstress_value=float: Shear stress coefficient; Shear stress coefficient; Default: 0.0
density=name: Sediment mass density; Sediment mass density in g/cm^3
density_value=float: Sediment mass density; Sediment mass density in g/cm^3; Default: 1.4
mass=name: Mass of sediment per unit area; Mass of sediment per unit area in kg/m^2
mass_value=float: Mass of sediment per unit area; Mass of sediment per unit area in kg/m^2; Default: 116.
grav_diffusion=float: Gravitational diffusion coefficient; Gravitational diffusion coefficient in m^2/s; Default: 0.1
erdepmin=float: Minimum values for erosion-deposition; Minimum values for erosion-deposition in kg/m^2s; Default: -0.5
erdepmax=float: Maximum values for erosion-deposition; Maximum values for erosion-deposition in kg/m^2s; Default: 0.5
start=string [required]: Start time in year-month-day hour:minute:second format; Default: 2016-01-01 00:00:00
rain_interval=integer [required]: Time interval between evolution events in minutes; Default: 1
temporaltype=name [required]: The temporal type of the space time dataset; Options: absolute, relative; Default: absolute
threads=integer: Number of threads for multiprocessing; Default: 1
elevation_timeseries=name [required]: Name of the output space time raster dataset; Default: elevation_timeseries
depth_timeseries=name: Name of the output space time raster dataset; Default: depth_timeseries
erdep_timeseries=name: Name of the output space time raster dataset; Default: erdep_timeseries
flux_timeseries=name: Name of the output space time raster dataset; Default: flux_timeseries
difference_timeseries=name: Name of the output space time raster dataset; Default: difference_timeseries

DESCRIPTION
EXAMPLES
ERROR MESSAGES
REFERENCES
SEE ALSO
AUTHORS

DESCRIPTION

r.sim.terrain is a short-term landscape evolution model that simulates topographic change for both steady state and dynamic flow regimes across a range of spatial scales. It uses empirical models (RUSLE3D & USPED) for soil erosion at watershed to regional scales and a physics-based model (SIMWE) for shallow overland water flow and soil erosion at subwatershed scales to compute short-term topographic change. This either steady state or dynamic model simulates how overland sediment mass flows reshape topography for a range of hydrologic soil erosion regimes based on topographic, land cover, soil, and rainfall parameters.

EXAMPLES

Basic instructions

A basic example for the North Carolina sample dataset. Install the add-on module r.sim.terrain. Copy the raster elevation map elev_lid792_1m from the PERMANENT mapset to the current mapset. Set the region to this elevation map at 1 meter resolution. Run r.sim.terrain with the RUSLE model for a 120 min event with a rainfall intensity of 50 mm/hr at a 3 minute interval. Set the empirical coefficients m and n to 0.4 and 1.3 respectively. Use the `-f` flag to fill depressions in order to reduce the effect of positive feedback loops.

g.extension  extension=r.sim.terrain
g.copy raster=elev_lid792_1m@PERMANENT,elevation
g.region raster=elev_lid792_1m res=1
r.sim.terrain -f elevation=elevation runs=event mode=rusle_mode rain_intensity=50.0 rain_duration=120 rain_interval=3 m=0.4 n=1.3

Figure: Net difference (m) for a dynamic RUSLE simulation of a 120 min event with a rainfall intensity of 50 mm/hr with a 3 minute interval.

Spatially variable soil and landcover

Clone or download the landscape evolution sample dataset with a time series of lidar-based digital elevation models and orthoimagery for a highly eroded subwatershed of Patterson Branch Creek, Fort Bragg, NC, USA.

Run r.sim.terrain with the simwe model for a 120 min event with a rainfall intensity of 50 mm/hr. Use a transport value lower than the detachment value to trigger a transport limited erosion regime. Use the -f flag to fill depressions in order to reduce the effect of positive feedback loops.

g.mapset -c mapset=transport location=nc_spm_evolution
g.region region=region res=1
r.mask vector=watershed
g.copy raster=elevation_2016@PERMANENT,elevation_2016
r.sim.terrain -f elevation=elevation_2016 runs=event mode=simwe_mode \
rain_intensity=50.0 rain_interval=120 rain_duration=10 walkers=1000000 \
detachment_value=0.01 transport_value=0.0001 manning=mannings runoff=runoff

Figure: Net difference (m) for a steady state, transport limited SIMWE simulation of a 120 min event with a rainfall intensity of 50 mm/hr.

For more detailed instructions and examples see this in-depth tutorial.

ERROR MESSAGES

If the module fails with

ERROR: nwalk (7000001) > maxw (7000000)!

then a lower nwalkers parameter value has to be selected.

REFERENCES

Harmon, B., Mitasova, H., Petrasova, A., Petras, V., 2019. r.sim.terrain: a dynamic landscape evolution model.
Mitasova H., Barton M., Ullah I., Hofierka J., Harmon R.S., 2013. 3.9 GIS-Based Soil Erosion Modeling. In J. F. Shroder, ed. Treatise on Geomorphology. San Diego: Academic Press, pp. 228-258. DOI: http://dx.doi.org/10.1016/B978-0-12-374739-6.00052-X.

AUTHORS

Brendan A. Harmon
Louisiana State University
brendan.harmon@gmail.com

SOURCE CODE

Available at: r.sim.terrain source code (history)