GIS-based frequency ratio and Shannon's entropy techniques for flood vulnerability assessment in Patna district, Central Bihar, India

The prime purpose of this study is to explore the use of RS and GIS for flood risk mapping in the Patna district in conjunction with the frequency ratio and entropy model. The variables such as elevation, LULC, rainfall, slope, distance from the river, TWI, and drainage density have played significant roles in causing floods in the study area. The flood vulnerability map has been generated and categorized as very high, high, moderate, low, and very low vulnerable flood areas. The validation of the results outcomes was conducted using the ROC curve, which indicates that the frequency ratio model for flood vulnerability mapping is more authentic, reliable and can assist in demarcating flood vulnerable areas and potential flood risk sites. The results show that about 16.35% (FR model) and 9.98% (SEI model) of the study area have come under very high risk of flooding, especially located in the southeast and northwestern sites of the district. The blockwise flood risk assessment shows that 13 out of 23 blocks recorded over 25% of their total area under very high flood risk. The present study reveals the usefulness of RS and GIS techniques along with bivariate models for the investigation and evaluation of flood vulnerabilities as they provide a wide range of data and reliable platforms. The results of this report will assist planners in developing flood prevention plans as part of regional flood risk management initiatives and will serve as a foundation for future studies in the study region.