Sub-watershed Prioritization of Ajay River Basin for Flood Susceptibility Analysis, West Bengal, India

The lower Ajay river basin is one of major flood-prone areas of West Bengal, floods in the Ajay river occur mostly during the monsoon season. Post-independence the river has faced several major flooding, i.e., 1956, 1959, 1970, 1971, 1973, 1978, 1984, 1995, 1999, 2000, 2006, 2007. The study attempts to assess the sub-watershed level flood susceptibility of the Ajay River Basin (ARB) using geomorphic and hydrologic parameters. Based on the parameters, the sub-watersheds have been prioritized using weighted sum analysis (WSA), and they have been assigned ranks based on their weightage to define the level of flood susceptibility. The result of the study shows that the downstream sub-watersheds are highly and very highly flood susceptible, which consists of 21.51% of the total basin areas. The drainage and topographic characteristics of these areas increase their flood susceptibility. Geospatial technology has been used as a major tool. The study will be helpful for sub-watershed-level flood management and risk assessment in the focused study area.