Integrating Analytical Hierarchy Process and Geographical Information Systems for Comprehensive Flood Risk Evaluation in Upputhara, Kerala

Floods are among the most common and costly natural hazards worldwide, significantly impacting the environment by affecting water quality, biodiversity and increasing pollution levels. Upputhara, located in the Idukki district of Kerala, experiences frequent flooding due to its location in a V-shaped valley of the Periyar river, just below the Mullaiperiyar and Idukki reservoirs. The primary aim of this study is to delineate a flood hazard map for the Upputhara Grama Panchayat using a geospatial-based Analytical Hierarchy Process (AHP). The data sources for this study include Survey of India (SOI) topographical maps, ASTER DEM (30-meter resolution) and rainfall data from the Indian Meteorological Department (IMD). The flood hazard map was generated using nine spatial layers: vegetation condition, rainfall, geology, elevation, flow accumulation, topographic wetness index, drainage density, slope and soil texture. The final map was produced through multi-criteria overlay analysis within a GIS environment, classifying the area into five flood hazard categories: very low (52%), low (28%), moderate (13%), high (5%) and very high (1.5%). Field data from flood-affected locations showed that the model has a 95% accuracy. While the majority of the study area faces a very low to moderate flood risk, about 17% of the region is at high to very high risk. This study demonstrates that geospatial technology-based flood hazard delineation is highly effective and supports sustainable development and planning. The generated map aids authorities responsible for flood protection by raising awareness about flood-prone areas and helping to reduce vulnerability.