Geo-spatial Variability of Physiographic Parameters and Landslide Potentiality - Semi-quantitative Approaches for Landslide Assessment and Prediction - page 76

Fig. 2.9 Spatial distribution of clay (%)

Lower part of study area is experiencing very minimum percentage of sand
particles whereas extreme south western part, small pockets in the south are
characterized by higher percentage of sand particles. Mid-section and most of the
marginal area are dominated by moderate to low percentage of sands (Table A.1,
Appendix A). Tindharia (26.5 km from Siliguri), Lower Paglajhora, Mahanadi and
Nurbong T.E. represents medium percentage of sand particles (Fig. 2.10 ) and this
situation provide numerous micro pore spaces within the sub-soil and consequently
increase the water holding capacity and reduce cohesive strength of the soil. In the
south eastern part mainly at Tindharia and Sepoydhura, Mahanadi, Upper Pag-
lajhora and Shiviter T.E. percentage of clay particles ranges from moderate to low
and so the bonding capacity is low. This leads to soil erosion and slope instability
condition. Small pocket in Giddapahar and Gayabari and lower eastern part register
with high percentage of clay particles (Fig. 2.9 ).
Giddapahar, Shiviter and Upper Paglajhora is experiencing fine sand, medium

sand, coarse sand and very coarse sand ranging between 10 and 30 % (Appendix
A). The percentage of coarse silt and

fine silt are very low (below 5 %) and

percentage of very ne sand ranges between 5 and 10 %. The study on the

distribution of silt particle in the Shivkhola watershed depicts that yet the