Geo-spatial Variability of Physiographic Parameters and Landslide Potentiality - Semi-quantitative Approaches for Landslide Assessment and Prediction - page 78

Fig. 2.11 Spatial distribution of silt (%)
the other tape was allowed to hang, the reading was then taken from the base of the
hanging tape. The total thickness of soil and that of saturated soil from 50 different
locations during monsoon were measured from slope cuttings. After estimating the
approximate depth of all known points, a soil depth map (z/D) was made using Arc
GIS tool (Fig. 2.13 ). The maximum depth (>1.75 m) of the saturated soil is found in
the middle section (lower segment of Gayabari T.E., lower Paglajhora, Lower
segment of Shiviter and Tindharia T.E.) and lower section (mainly Nurbong and
Sepoydhura T.E.) of the basin. At marginal parts of the basin basically on the both
sides of the Hill Cart Road from Chunabhati to Gayabari, upslope parts from
Paglajhora proper, Lezzipur T.E. and Shiviter upslope, the saturated soil depth is
less than 1.75 m (Table A.1, Appendix A).
In the present study area, Shivkhola watershed the upper section of the soil at
major landslide locations are predominated by large percentage sand particle where
the tensile strength in dry and wet situation is low (Table 2.9 ). This situation
promotes shallow landslips. But the area dominated by large percentage of clay and