Tool LS-Factor, Field Based
Calculation of slope length (LS) factor as used for the Universal Soil Loss Equation (USLE), based on slope and (specific) catchment area, latter as substitute for slope length. This tool takes only a Digital Elevation Model (DEM) as input and derives catchment areas according to Freeman (1991). Optionally field polygons can be supplied. Is this the case, calculations will be performed field by field, i.e. catchment area calculation is restricted to each field's area.
References:
Boehner, J., Selige, T. (2006): Spatial Prediction of Soil Attributes Using Terrain Analysis and Climate Regionalisation. In: Boehner, J., McCloy, K.R., Strobl, J.: 'SAGA - Analysis and Modelling Applications', Goettinger Geographische Abhandlungen, 115, 13-27.
Desmet, P.J.J., Govers, G. (1996): A GIS Procedure for Automatically Calculating the USLE LS Factor on Topographically Complex Landscape Units. Journal of Soil and Water Conservation, 51(5), 427-433.
Freeman, G.T. (1991): Calculating catchment area with divergent flow based on a regular grid. Computers and Geosciences, 17:413-22
Kinnell, P.I.A. (2005): Alternative Approaches for Determining the USLE-M Slope Length Factor for Grid Cells. https://www.soils.org/publications/sssaj/abstracts/69/3/0674
Moore, I.D., Grayson, R.B., Ladson, A.R. (1991): Digital terrain modelling: a review of hydrogical, geomorphological, and biological applications. Hydrological Processes, 5(1).
Moore, I.D., Nieber, J.L. (1991): Landscape assessment of soil erosion and nonpoint source pollution. J. Minnesota Acad. Sci., 55, 18-25.
Wischmeier, W.H., Smith, D.D. (1978): Predicting rainfall erosion losses - A guide to conservation planning. Agriculture Handbook No. 537: US Department of Agriculture, Washington DC.
- Author: O.Conrad (c) 2013
- Menu: Terrain Analysis|Hydrology|Topographic Indices
Parameters
Name | Type | Identifier | Description | Constraints | |
---|---|---|---|---|---|
Input | Elevation | Grid (input) | DEM | - | - |
Fields (*) | Shapes (optional input) | FIELDS | - | - | |
Output | Field Statistics (*) | Shapes (optional output) | STATISTICS | - | - |
Upslope Length Factor (*) | Grid (optional output) | UPSLOPE_AREA | - | - | |
Effective Flow Length (*) | Grid (optional output) | UPSLOPE_LENGTH | - | - | |
Upslope Slope (*) | Grid (optional output) | UPSLOPE_SLOPE | - | - | |
LS Factor | Grid (output) | LS_FACTOR | - | - | |
Sediment Balance (*) | Grid (optional output) | BALANCE | - | - | |
Options | Grid system | Grid system | PARAMETERS_GRID_SYSTEM | - | - |
LS Calculation | Choice | METHOD | - | Available Choices: [0] Moore & Nieber 1989 [1] Desmet & Govers 1996 [2] Wischmeier & Smith 1978 Default: 0 | |
Type of Slope | Choice | METHOD_SLOPE | - | Available Choices: [0] local slope [1] distance weighted average catchment slope Default: 0 | |
Specific Catchment Area | Choice | METHOD_AREA | - | Available Choices: [0] specific catchment area (contour length simply as cell size) [1] specific catchment area (contour length dependent on aspect) [2] catchment length (square root of catchment area) [3] effective flow length Default: 1 | |
Stop at Edge | Boolean | STOP_AT_EDGE | - | Default: 1 | |
Rill/Interrill Erosivity | Floating point | EROSIVITY | - | Minimum: 0.000000 Default: 1.000000 | |
Stability | Choice | STABILITY | - | Available Choices: [0] stable [1] instable (thawing) Default: 0 | |
(*) optional |
Command-line
Usage: saga_cmd ta_hydrology 25 [-DEM <str>] [-FIELDS <str>] [-STATISTICS <str>] [-UPSLOPE_AREA <str>] [-UPSLOPE_LENGTH <str>] [-UPSLOPE_SLOPE <str>] [-LS_FACTOR <str>] [-BALANCE <str>] [-METHOD <str>] [-METHOD_SLOPE <str>] [-METHOD_AREA <str>] [-STOP_AT_EDGE <str>] [-EROSIVITY <double>] [-STABILITY <str>] -DEM:<str> Elevation Grid (input) -FIELDS:<str> Fields Shapes (optional input) -STATISTICS:<str> Field Statistics Shapes (optional output) -UPSLOPE_AREA:<str> Upslope Length Factor Grid (optional output) -UPSLOPE_LENGTH:<str> Effective Flow Length Grid (optional output) -UPSLOPE_SLOPE:<str> Upslope Slope Grid (optional output) -LS_FACTOR:<str> LS Factor Grid (output) -BALANCE:<str> Sediment Balance Grid (optional output) -METHOD:<str> LS Calculation Choice Available Choices: [0] Moore & Nieber 1989 [1] Desmet & Govers 1996 [2] Wischmeier & Smith 1978 Default: 0 -METHOD_SLOPE:<str> Type of Slope Choice Available Choices: [0] local slope [1] distance weighted average catchment slope Default: 0 -METHOD_AREA:<str> Specific Catchment Area Choice Available Choices: [0] specific catchment area (contour length simply as cell size) [1] specific catchment area (contour length dependent on aspect) [2] catchment length (square root of catchment area) [3] effective flow length Default: 1 -STOP_AT_EDGE:<str> Stop at Edge Boolean Default: 1 -EROSIVITY:<double> Rill/Interrill Erosivity Floating point Minimum: 0.000000 Default: 1.000000 -STABILITY:<str> Stability Choice Available Choices: [0] stable [1] instable (thawing) Default: 0