Tool Name	LS Factor
Tool ID	22
Library ID	ta_hydrology
Version	1.0
Author(s)	O.Conrad (c) 2003

Description

Calculation of slope length (LS) factor as used by the Universal Soil Loss Equation (USLE), based on slope and specific catchment area (SCA, as substitute for slope length).

References

Böhner, J., Selige, T. (2006): Spatial Prediction of Soil Attributes Using Terrain Analysis and Climate Regionalisation. In: Böhner, J., McCloy, K.R., Strobl, J.: SAGA - Analysis and Modelling Applications. Göttinger Geographische Abhandlungen, Vol.115, p.13-27. PDF

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. doi:10.1080/00224561.1996.12457102

Kinnell, P.I.A. (2005): Alternative Approaches for Determining the USLE-M Slope Length Factor for Grid Cells. Soil Sci. Soc. Am. J., 69: 674-680. doi:10.2136/sssaj2004.0047

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. doi:10.1002/hyp.3360050103

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.

Parameters

Name	Type	Identifier	Description	Constraints
Input
Slope	grid, input	SLOPE
Catchment Area	grid, input	AREA
Output
LS Factor	grid, output	LS
Options
Unit	choice	SLOPE_UNIT		Available Choices: [0] radians [1] degree Default: 0
Area to Length Conversion	choice	CONV	Derivation of slope lengths from catchment areas. These are rough approximations! Applies not to Desmet & Govers' method.	Available Choices: [0] no conversion (areas already given as specific catchment area) [1] 1 / cell size (specific catchment area) [2] square root (catchment length) Default: 0
Feet Adjustment	boolean	FEET	Needed if area and lengths come from coordinates measured in feet.	Default: 0
Method (LS)	choice	METHOD		Available Choices: [0] Moore et al. 1991 [1] Desmet & Govers 1996 [2] Böhner & Selige 2006 Default: 0
Rill/Interrill Erosivity	floating point number	EROSIVITY		Minimum: 0.000000 Default: 1.000000
Stability	choice	STABILITY		Available Choices: [0] stable [1] instable (thawing) Default: 0