Vesta-Little North Tributaries of the Chehalis
Mapped Stability at phi=45°, Coh=0 kN/mē
Analysis with stability.aml created:
qust45: rainfall for instability in the old fashion, using a q and no cohesion,
qust15: rainfall for instability, with phi = 45°, choh = 15kN/mē,
qust8: rainfall for instability, with phi = 45°, choh = 8kN/mē,
qust2: rainfall for instability, with phi = 45°, choh = 2kN/mē, and
critcoh100: critical cohesion, assuming a steady-state rain of 100mm/day.
Comparison with Field Data
The landslide coverage has 262 slide polygons, 180 road-related, 75 not, 3 'i'.
slides 379-382 have no data-base entries (but are als).
The slide categories are
The background polygon--and some slivers--have no code.
Only debris flows and shallow rapid flows will be tallied.
The 4 roadtype = "i" will be tallied with the non-road slides.
When we rasterize the slides on a 30-meter grid with the standard ARC/INFO
algorithm, 13 slides fall through the cracks. The best solution is to
force rasterization to count a cell as a slide if it touches a slide at all.
We can tally results by polygonal slide area or by slide count. Slide areas
are problematic, because slides were digitized to include runout paths.
|ssd||small sporadic deep (slumps),
|df||debris flow, and
Some slides are represented as two or more polygons, we our clever
compilation program can work around this problem.
NOTE: The shallow slumps were accidentally included in the road-related
column. Tables were updated May 15. The difference is 2 slides.
NOTE: The Not-road-related column of the normalized table for each case
were incorrect until corrected on May 31 but you must have seen that.
Here are results for