Slope-Length

Baxter E. Vieux vieux at chief.ecn.uoknor.edu
Sat Feb 11 06:25:01 EST 1995


The slope length (LS) has nothing to do with raster grid cell resolution.
It is related to the length that water travels as runoff from the top
of the slope to where two rills form. Thus, it is problematic to incorporate
this factor into an erosion estimate using a GIS. Unless you have a detailed
map of this length, you have to use typical values for the region. Another
method relies on some topographic shape factors derived from the convexity
and concavity of the slope. However, the latter cannot account for the the
point where two rills join, so it is doubtful that it is really what the
USLE, MUSLE, RUSLE models want. We typically survey the watershed for typical
slope lengths. These are generally consistent for soil types since geomorphological factors that produced the soils also formed the slope lengths. If a 
particular region of the watershed has long slope lengths, you can map these
areas and incorporate them into the model. 

We have done a number of CWA Sec 314 nonpoint studies for our Water Resources
Board. If you would like a copy of a report, send me your address and I will
send!:-)

Cheers--
Baxter Vieux



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