Addendum to “The USLE-M and modeling Erosion catchments”

Eq. 20 has now been replaced by

Q_Ce.i,j-eff (A_i,j-in.eff + D²)^m+1 - Q_Ce.i,j-eff A_i,j-in.eff^m+1
L_UMe.i,j = ———————————————————
Q_Re.i,j-cell D^m+2 x_i,j^m (22.13)^m

where

Q_Ce.i,j-eff = [(Q_Ce.i,j-cell D²) + (Q_Ce.i,j-in A_i,j-in.)] / (A_i,j-in.eff + D²)

.

and

Ai,j-in.eff = Ai.j-in QCe.i,j-in / QCe.i,j-all

The original approach developed by Desmet and Govers (1996) for determining the L factor for grid cells applies where runoff is produced uniformly over the whole area contributing runoff to the cell so that the runoff coefficient for the cell (Q_Ce.i,j-cell) equals that of the upslope area (QCe.i,j-in). When runoff is zero, the upslope area is effectively zero. In the context of determining the slope length factor for a cell, the approach given above considers the upslope area to vary depending on the ratio of the runoff ratio of the upslope area to that of the whole area (QCe.i,j-all). Details of the approach are subject to a paper to be published in the Soil Science Society of America Journal and the approach is used in the current software applying the USLE-M within AGNPS (AGNPS-UM) available from this WWW site.

Read The USLE-M and modeling erosion within catchments

peter.kinnell@canberra.edu.au 3 Nov 2004.