Sediment Delivery Ratio - very high values
I ran the Sediment Delivery Ratio model with InVEST 3.2.0
for a study area in the Ethiopian highlands obtaining very high values. For
example the usle ranges between 0 and almost 500000 with a mean of 3500. For
comparison I calculated the usle with GRASS GIS using the same data. In this
case the results are lower, between 0.6 and 18000 with a mean of 240. With
further investigation I realised that maps of length slope calculated by InVEST
and GRASS (using r.watershed module, https://grass.osgeo.org/grass70/manuals/r.watershed.html)
are very different. In GRASS GIS the minimum slope length is 0.03, maximum = 24
and mean = 0.4, while in Invest minimum
= 0.05, maximum = 1174 and mean = 8.5.
I am wondering if this is expected behaviour of InVest ? In
this case how this can be explained? Or
is there something that I am missing?
Thanks in advance for your help.