A series of simulations of slope stability based a digital elevation model
This 7.5' quadrangle came to us from Peerless
Management Systems [This page was created before the USGS had published
many 10-meter DEMs.] as contour
lines (from the USGS topo sheet) and as a 10-meter DEM. It was slightly
cropped for our work. We modified the DEM (as we modify all DEMs) by
filling sinks and by incrementing cells by one-millimeter so that water
would know how to flow off flat spots.
We applied our own algorithm and C program to calculate contributing area.
This information is brought into ARC/INFO® format, and subsequent modeling
is implemented through aml (arc macro language) files. The following images
show critical rainfall (the amount of steady-state rain in mm/day)
necessary to destabilize a slope. Soil cohesion (principally provided by
roots) varies from 0 to 8 kilonewtons/mē in the three images.
We can set rainfall to a constant 100 mm/day, and examine the critical
cohesion of each landscape element. We start with the original DEM, and
then degrade it to a cell size of 30, 60, 90, and 120 meters by averaging elevations.