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Friday, March 4, 2016

Calculation of Slope Length Factor LS Factor in ArcGIS



where A[r] is upslope contributing area per unit contour width, b [deg] is the slope, m and n are parameters, and a0 = 22.1m = 72.6ft is the length and b0 = 0.09 = 9% = 5.16deg is the slope of the standard USLE plot. The values of m (=0.6) and n (=1.3) were empirically derived.

The LS factor was then computed using Raster Calculator in ArcGIS to build an expression for estimating LS, based on flow accumulation and slope steepness.

The expression is:
In older Veriosn of ArcGIS as Follow: upto 9.3

(([flowacc] * resolution/22.1).Pow(0.6))*(((([slope]*0.01745).Sin)/0.09).Pow(1.3))*1.6

New Version of ArcGIS from 10.1 to Present as Follow

Power(("%flowacc%") * 30 / 22.1,0.6)*Power(Sin("%slope_deg%") * 0.01745 / 0.09,1.3)*1.6

where Pow (which then means power) is a function in the ArcGIS spatial Analyst