An assessment of flood susceptibility using AHP and frequency ratio (FR) in the Lakhimpur district of Assam, India

Flood is one of the most devastating disasters throughout the globe that damages the natural over and above the human environment. It is important to ascertain the flood susceptibility regions to minimize the impact of flood for socio-economic development. The present study tries to assess the flood susceptibility regions of the Lakhimpur district based on the Analytical Hierarchy Process (AHP) and Frequency Ratio (FR) integrating five susceptibility indicators such as Elevation, Average Annual Rainfall, Stream Density, Distance from River, and Land Use and Land Cover (LULC). The output maps for both the models were generated assigning three susceptibility classes such as Frequently Flood Affected Zone, Occasionally Flood Affected Zone, and Flood Free Zone. The AHP model reveals that 34.63% of the area in the district is under the Frequently Flood Affected Zone, 46.79% and 18.58% of the area is under Occasionally Flood Affected Zone and Flood Free Zone respectively. On the contrary, the FR model reveals that 17.65% of the area in the district is under the Frequently Flood Affected Zone, 42.92% and 39.43% of the area is under Occasionally Flood Affected Zone and Flood Free Zone respectively. Both the results were validated with one statistical operation along with ground truth data. The Area under Curve (AUC) in Receiver Operating Characteristics (ROC) was employed to validate the models. For the AHP model, the AUC was recorded 69.72% and 75.77% for the FR model which are significantly good accuracy for the flood susceptibility mapping. For the ground truth validation of the models, the historic flood events recorded by satellite data (2007, 2008, and 2018) and flood data from the last 5 years were also incorporated. The ground truth data shows that the result from the FR model is very close to the flood susceptibility zones in the historic events. The result revealed from both the models will help the local administration and planners for effective flood monitoring and management.