Modelling of Flood Susceptibility Based on GIS and Analytical Hierarchy Process—A Case Study of Adayar River Basin, Tamilnadu, India

Abstract

Among the most devastating natural disasters, flood stands tall. India is one of the countries affected by flood almost every year. Inclusive flood management is necessary to retard the implications of the vulnerability over the human lives and livelihoods. The objective of present study is to demarcate and categorize the flood hazard and risk assessment zones using analytical hierarchy process (AHP) and geographical information (GIS) in the Adayar River basin, Tamilnadu, India. Integrating AHP with GIS provides more optimum decisions to the decision-makers to evaluate the effective factors. The study area is an urbanized watershed, which lies between 12° 45′–13° 15′N latitude and 79° 50′–80° 15′E longitude covering a total geographical area of 830 km2. The flood inventory map was prepared by using extensive field data collected in 2015 December flood event. Nine base layers such as rainfall, elevation, land-use, lithology, distance from rivers, soil texture, slope angle, drainage density and topographic wetness index (TWI) were prepared from the spatial database using ArcGIS 10.4. Flood frequency map was generated from the long-term observed rainfall data. Flood inundated areas were classified as very low, low, moderate, high and very high based on its susceptibility to the probability of flood hazard. Suitable scores were assigned to each class for determination of risk zone. The incorporation of all thematic layers and the generated flood frequency map was used to prepare the flood susceptibility and flood hazard using GIS platform. Results indicated that the flood susceptibility zone in different scales, i.e. very high 30,200 ha (36.39%), high susceptibility 9,400 ha (11.33%), moderate susceptibility 15,200 ha (18.31%), low susceptibility 17,900 ha (21.57%) and very low susceptibility 10,300 ha (12.41%). The final suitability model outputs were compared with field data and are acknowledged as a useful product for the district planners to take the necessary steps to manage the flood susceptible areas from damages by implementing of flood controllers and prevention measures.