Morphometric Analysis to Prioritize for Flood Risk of Sub-Watersheds of Teesta (Sikkim and West Bengal) Through Hazard Degree (HD) and Principal Component Analysis with Weighted Sum Approach (PCAWSA)

Abstract

Risk assessment is an effective tool for flood monitoring and mitigation since it identifies flood-prone areas. In terms of flood dynamics and watershed priori-tisation, morphometric parameters play an essential role. Morphometric analysis can be used to prioritise sub-watersheds for flood potential mapping by examining the linear, aerial and shape aspects of the watershed. Fifteen parameters such as Stream order, number of Streams, Stream length, Bifurcation Ratio, Basin Length, Basin Area, Basin perimeter, Elongation ratio, Shape factor, Drainage density, Drainage texture, Stream frequency are selected for the evaluation of flood risk assessment. The Digital Elevation Model (DEM) was used to delineate the watershed and drainage network using Arc GIS. On the basis of Morphometric Hazard Degree (MHD) and Principal Component Analysis (PCA) with Weight Sum Approach (WSA), 14 sub-watersheds are prioritized. The values that have a high effect on floods are rated according to their priorities in the assessment of the results obtained. The findings were evaluated in terms of flood priorities using hazard score and compound factor. Watershed flood priorities are graded as high, medium, or low based on the results of two different methods. The number of common watersheds 01 with “high” priority, 04 with “medium” priority, and 05 with “low” priority, as calculated by two sepa-rate methods. Hazard index-based findings showed that Rangit (SW-5) is under a highly susceptible zone. While sub-watersheds SW-1, SW-3, SW-4, SW-9 and SW-14 are moderately susceptible to flood risk. PSAWSA based approach suggests that sub-watersheds SW-1, SW3, SW-5, SW-13have high flood susceptibility.