DEFORESTATION AROUND THE WORLD - India Environment Portal

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Deforestation Around the World
slip lower boundary condition, the creeping rate usually is imperceptible (below 53 m in
Fig.5) before reaching the granular layer.
Fig. 5. The observed (markers) and modeled (lines with same style) displacement-time
curves for BH8.
The absence of vegetative root strength binding soils increases susceptibility to sliding in
loose soil on steep slopes during intense rainstorms (Dietrich and Perron 2006). Extra
biomass loading also may contribute to slope instability during wet seasons. Ground surface
biomass loading information for YC, because of its limited extent of only ~20 km 2, was
collected by a geological survey team following a request by the first author.
Using mean annual soil moisture conditions (obtained from NCEP/NCAR reanalyses,
http://www.cdc.noaa.gov/data/gridded/data.ncep.reanalysis.surfacefluxes.html), a
creeping rate is simulated using the SEGMENT model near BH8 of 17, 17.2, 16.2, 8.5, 5.2 and
3.1 mm/yr respectively at 1.5, 3, 10, 30, 40 and 45 m depths, agreeing well with the observed
measurements. The root mean squared error, when compared with the 108 measurement
data grids, is overestimated by only 0.42 mm/year, well within instrumental error range.
The depth of the sliding surface (49 m at this location) is accurately delineated. Sliding will
eventually accelerate along this plane of weakness, which is composed of highly fractured
sandy shale. Interestingly, under natural conditions, the creeping speed curve is not a
simple dilatant profile: there are local minima/maxima. The faster creeping locations near