Risk Assessment and Categorization of Flood Risk Zones Using Geospatial Data and Multi-Criteria Decision Model in a Low-Lying Deltaic Region, Kuttanad, India

Non-sustainable land use results in induced climate change and severe hydrologic hazards all over the world. Now a days, floods play a significant role in destructing the environment and human lives. The present study uses geospatial data with thirteen flood conditioning criteria to identify the flood risk in a deltaic region, Kuttanad. Eight physical- geological criteria such as elevation, drainage density, geology, flow accumulation, slope, Stream Power Index (SPI), Topographic Wetness Index (TWI) and Standard Curvature (SC) were used for vulnerability studies. Three socio-economic factors such as population density, Land Use and Land Cover (LULC) and road density were included to identify the flood exposure. Precipitation and river density were considered to identify the flood hazard. The above criteria were integrated by the method of spatial integration in the ArcGIS environment to identify the area subjected to flood risk. Subjective judgements made using the above criteria were converted into quantitative data based on Analytical Hierarchy Process (AHP) scale. Essential judgements of this study demonstrated that a critical percentage of the region (68%) comes under high flood vulnerability. 34% of the area comes under high hazardous regions and they need immediate attention. Integrating vulnerability, exposure and hazard, a flood risk map was prepared and found that nearly 72% of the region comes under high-risk. Efficiency of the flood risk and flood vulnerability map tested by Area Under Curve (AUC) indicates a higher precision, by obtaining 89% accuracy for the flood risk map and 93% for the flood vulnerability map. The mean value of the flood risk index in 6 agro-ecological zones has been computed and distributed evenly by the method of zonal statistics to identify the flood risk zone. Flood risk index ranging from 2.84 to 3.10 is classified under Zone I, 2.72–2.78 under Zone II, 2.71 under Zone III and 2.61 is classified as Zone IV respectively. The results obtained from this study enable prioritization of flood risk areas, offering valuable insights for planners, decision makers to control and alleviate flood events along the deltaic region, Kuttanad.