Flood Hazard Zone Mapping of Vashishti River Basin by Using Remote Sensing and GIS Techniques

Abstract

Floods are among the most destructive natural hazards in regions characterised by high and intense rainfall, frequently causing substantial loss of human life and considerable damage to agriculture, infrastructure, property, and the natural environment. The Vashishti River basin, situated within the ecologically sensitive Western Ghats, is particularly susceptible to recurrent and severe flooding owing to its distinctive hydro-meteorological and physiographic characteristics. The interaction of intense monsoonal rainfall, basin topography, drainage conditions, and increasing human intervention further contributes to the basin's flood susceptibility. In this context, flood hazard mapping provides an effective means of identifying areas with varying levels of exposure to flooding and can support the reduction of disaster risks associated with human settlements, agricultural activities, infrastructure development, and, in particular, expanding urban areas. Therefore, the present study aims to identify, delineate, and characterise flood hazard zones within the Vashishti River basin. The resulting spatial information is expected to provide a scientific basis for improved flood risk assessment, land-use planning, disaster preparedness, and the formulation of effective flood mitigation and management strategies. A total of ten flood-influencing factors, namely elevation, slope, drainage density, distance from the river, land use/land cover, rainfall, runoff derived using the SCS-CN method, geomorphology, lithology, and soil texture, were analysed in a Geographic Information System (GIS). Weights were assigned using the Analytic Hierarchy Process (AHP). With a consistency ratio (CR) of 0.06 for the correlation matrix, the flood hazard zone map indicates that 0.81% of the study area falls within a very low hazard zone, 13.49% within a low hazard zone, 47.90% within a moderate zone, 20.59% within a high flood hazard zone, and 17.20% within a very high flood hazard zone. Rainfall, elevation, and slope are the primary factors influencing flood risk. The AHP-based approach used in this study provides a practical framework for flood hazard mapping and may be applied to other regions for flood hazard management and mitigation.