Flood Assessment for Lower Godavari Basin by using the application of GIS-based Analytical Hierarchy Process

The Godavari River is the principal river in southern India having one of the largest river basins. Several locations in the lower Godavari basin are susceptible to flooding due to the various natural hazards. The region is densely populated and has important land features making it vulnerable to floods. Thus, the combined effect of hazards and vulnerability leads to risk. Considering the strategic importance of the basin, a study is performed to assess flood risk in the lower Godavari basin. There are several methodologies available for flood risk analysis that have been used by various investigators in the past. In the present work, flood risk is assessed using a multiparametric approach known as the Analytical Hierarchy Process (AHP), which is one of the most advanced and contemporary techniques for decision-making. In this study, the decision factors are considered for calculating the Flood Hazard Index (Rainfall, Slope, Drainage Density, Distance to Stream, Topographic Wetness Index, Stream Power Index, and Sediment Transport Index) and the Flood Vulnerability Index (Population Density, Land Use Land Cover). A detailed map is generated using Arc-GIS for each decision factor and the risk is classified as ‘Very High’, ‘High’, ‘Moderate’, ‘Low’, and ‘Very Low’ based on parametric values. The calculation of flood hazard and flood vulnerability indices is followed by the Flood Risk Index (FRI). Subsequently, the desired FRI map for the lower Godavari basin is generated by identifying the risk zones.