Flood Susceptibility Assessment Using Geospatial Multi-Criteria Framework: A Study in Lower Mahananda Basin, India

Abstract

Flood is the common natural hazard in the plains of Lower Ganga that causes considerable damage to the society and its infrastructure every year. During the monsoon, Mahananda river carries voluminous discharge and often it overtops the bank and spills out to the surrounding plains, especially in the northern parts of Bihar and West Bengal. Therefore, an attempt has been made to identify and assess the flood risk prone area in the comprised zone of Lower Mahananda basin, India. Seven geospatial parameters have been incorporated to the weighted overlay analysis in GIS environment using multi-criteria based analytical hierarchy process (AHP). The prepared final map is classified into five spatial zones considering their susceptibility to the flood. In this regard, cross-sectional profile of the river at six different sites was made for assessing the water level during the flood. The very high flood susceptible zone comprises about 64.46 km2 area (0.80%) and remains waterlogged for most part of the year. The high flood susceptible zone is consists of 1441.38 km2 of area (17.99%) and widely spread over the populated zone of Malda district when water level in the channels can rise up to 3m from its normal level. The bulk of the area (56.02%) falls in the moderate category and the chances of inundation here only during the major floods. The reliability of the model has been assessed using the AUC, where the accuracy is more than 80%. The overall framework is thus useful for policy implementation and mitigation purposes.