Flood risk assessment in the Kosi megafan using multi-criteria decision analysis: A hydro-geomorphic approach

Abstract

Floods are one of the most devastating natural events that leadto enormous and recurring loss of life, properties,and resources around the globe. In India, floodsremaina recurrent event during the monsoon season in many parts of the country but most seriously in the flat and monotonous Gangetic plains inthe Himalayan foreland. One of the most flood-prone rivers in India is the Kosi in north Bihar, eastern India, which also forms the largest active megafan in the world. The Kosi River is known as the “sorrow of Bihar” because of its anomalous behavior and the damage it causes due to frequent floods in this region. This study evaluates the flood hazardandflood vulnerability as separate entities, and combines them to assess flood risk in the Kosi megafan region. Geomorphological, hydrological, and socio-economic data have been integrated ina GIS framework using a multi-criteria decision tool called the Analytical Hierarchy Process (AHP) to generate a process-based flood risk map for 105 blocks (administrative units) of both Nepal and India (Bihar). Such maps should encourage soft engineering solutions for flood mitigation aimed at minimizing the consequences of flooding and reducing the flood risks. This study has significant implications for developing measures and plans that will help government and relief agencies in the identificationof flood-proneareas and forplanning emergency management strategies in this region.