Classification of Sub-Watersheds with Respect to Flooding Susceptibility in a Tropical River Basin Using Multi Criteria Approach Based on VIKOR

Morphometric analysis is important for conservation and management of watersheds including flood control measures, which is in turn related to topographical components. Prioritization of sub-watersheds based on morphometric factors is carried out to understand the vulnerability of different sub-watersheds to hazards like flooding, soil erosion and groundwater storage. It is carried out in the initial phase so as to enhance the efficacy in selection of water and soil management and remedial practices. In the present study, prioritization is attempted using multi criteria approach based on VIKOR on the sub-watersheds of Mahe river basin in southwest India vis-à-vis their susceptibility to flooding. Thirteen morphometric factors pertaining to twelve sub-watersheds of the river basin are used in the present analysis and they are classified (High, Moderate and Low) based on their risk of flooding. Sub-watersheds 3–8, upstream of the Mahe were identified as being the most prone to flooding. Sub-watersheds 1 and 2, offer a moderate risk of flooding, since the advantage of prominent runoff in their upper reaches is inhibited by the laterite dominated terrain downstream. The sub-basins 9–13 in the coastal plains, forming ~ 60% of total area of Mahe basin, fall in ‘Least’ category. The prioritization of sub-watersheds based on Multi Criteria Decision Analysis of their morphological factors is found to be useful in the discrimination of flooding prone areas. This would help in the selection of suitable management and remedial measures for the sub-watersheds based on their hazard of flooding.