Flood Risk Mapping for Tlawng River Basin in Mizoram

Abstract

Floods are among the worst devastating catastrophes on earth, leading to substantial loss of life and harm to buildings and infrastructure. 1.47 billion individuals worldwide face the threat of flooding. The Northeastern region of India, including Mizoram, is particularly vulnerable due to its hilly terrain, fragile ecosystem, and heavy monsoon rainfall. The Tlawng River, the longest river in Mizoram (185 km within the state), experiences frequent flooding, with the most recent major flood in 2019 affecting 1,968 families across 205 villages. Despite the devastating impacts of floods in the region, a comprehensive flood risk assessment has not yet been carried out for the entire Tlawng River Basin. The present research integrates a GIS-based MCA with AHP to develop a flood risk assessment for the Tlawng River Basin. Flood hazard indicators, consisting of MNDWI, NDVI, distance to river, slope, drainage density, TWI, elevation, rainfall, and lithology, were analyzed alongside vulnerability indicators such as LULC, population density, and proximity to roads and hospitals. Spatial layers for each indicator were generated, and their relative weights were determined using pairwise comparisons in the AHP framework. The study generated a final flood risk map by integrating assessments of flood hazards and vulnerabilities. The findings show that high and very high flood-risk areas encompass approximately 41.6% (1,445.7 km²) of the study region.