[GRASS-user] LS faktor in r.watershed

[Stefan Luedtke]

Dear friends, 

I am working with the r.watershed module in order to compute the LS
Faktor for (R)evised-Universal-Soil-Loss-Equation. For this option in
the module, I have to set the threshold for the minimum size of exterior
watersheds. There are many options out there to compute the LS-factor,
but I could not find the paper/report/.. that describes the algorithm
used in GRASS. 

Revised Universal Soil Loss Equation for Western Rangelands (Weltz et
al. 1987).

I want to understand why I need to set this threshold if I want
r.watershed to compute the LS -factor. So if somebody could help me
with:

a) the reference, so I can check by my self. 
or
b) a short explanation why this parameter must be set. 

By the way, I tested r.watershed with several thresholds (resulting in 1
big subbasin up to several hundreds) but the results for the Ls factor
hardĺy changed. 

Thanks in advance, 

Stefan

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