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. soil.scijournals.org, 69/3/674 http://soil.scijournals.org/cgi/content/full/69/3/674.
• Moore, I.D., Grayson, R.B., Ladson, A.R. (1991): Digital terrain modelling: a review of hydrogical, geomorphological, and biological applications. Hydrological Processes, Vol.5, No.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

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, input, optional
  -STATISTICS:<str>    	Field Statistics
	Shapes, output, optional
  -UPSLOPE_AREA:<str>  	Upslope Length Factor
	Grid, output, optional
  -UPSLOPE_LENGTH:<str>	Effective Flow Length
	Grid, output, optional
  -UPSLOPE_SLOPE:<str> 	Upslope Slope
	Grid, output, optional
  -LS_FACTOR:<str>     	LS Factor
	Grid, output
  -BALANCE:<str>       	Sediment Balance
	Grid, output, optional
  -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