Assessment of erosion susceptibility zones in Diring-Thanglong Watershed North Eastern Hill Regions of Assam using GIS techniques

Abstract

Assessment of erosion susceptibility zones has gained importance in natural resources management. The present study deals with erosion susceptibility zones through characterization of drainage morphometric parameters of Diring-Thanglong watershed of Assam state using Geographic Information System (GIS). The watershed showed high drainage density (2.75), bifurcation ratio (2.99) and stream frequency (3.59) and low circulatory ratio (0.58), elongation ratio (0.63) and length of overflow (0.18) with 5th order drainage stream, explaining the complex geomorphic processes occurring in the region due to variability in geological formations. Landform analysis was carried out through generation of various surface features viz., digital elevation model (DEM), slope, hill shade as well as by interpretation of satellite imageries and vigorous ground truth collections. Nine geomorphic units were identified in the watershed. Erosion susceptibility zones were recognized in various geomorphic units based on ranking of morphometric parameters. Severe to very severe erosion susceptibility was observed on valleys and piedmonts, whereas, moderate erosion susceptibility was observed on steep hills, isolated hillocks and foot hill plains. Rapid stream response was responsible for severity of erosion, whereas, dense vegetative/ forest cover was responsible for controlling the risk of erosion.