Impact Assessment of Hydrologic Attributes and Slope Instability

Abstract

Quantitative geomorphology provides a systematic approach to the analysis of a complex landscape of any size. The stability of the mountain slope depends upon the prevalence of various hydrologic variables. In the present work, the excess and deficit moisture period in a year and its role in slope instability were assessed studying rainfall and evapotranspiration. Study envisages that July and August are the most consistent rainfall months of the year where the values of co-efficient of variation are very low. The distribution of drainage and its evolution has been studied to determine the drainage concentration over the slope surface and their role in slope steepening and instability. To assume the slope saturation of materials saturation, stream confluence points/junction points were studied for individual sub-watersheds. The length of drainage per unit area and upslope contributing area were analyzed spatially in connection to the landslide potentiality. The existence of moderate drainage density may invite havoc slope failure on convex slope segment. Greater the upslope contributing area, maximum is the slope saturation and slope instability in the Shivkhola watershed. Some important drainage basin parameters such as basin shape, form factor, circularity ratio, elongation ratio, compactness factor, and elipticity index of the sub-watersheds were considered to develop the priority scale on slope instability. The sub-basin I and IV are more efficient in drainage and are more erosion and landslide prone followed by sub-watershed V, II, III and VI.