Quantitative Morphometric Analysis and Prioritization of Sub-Watersheds for Soil Erosion Susceptibility: A Comparison between Fuzzy Analytical Hierarchy Process and Compound Parameter Analysis Method

The identification of critical sub-watersheds susceptible to soil erosion risk is the preliminary step in any watershed management plan. To achieve this goal, it is crucial to prioritize sub-watersheds based on morphometric characteristics. This study was performed on the Upper Shimsha-1 watershed using a digital elevation model to quantify the morphometric parameters. The stream network was extracted using ArcGIS software, and the watershed was delineated into 16 sub-watersheds (denoted as SW1–SW16). Two approaches, namely, the fuzzy analytical hierarchy process (FAHP) and compound parameter analysis, were employed to prioritize sub-watersheds using 18 parameters highly related to soil erodibility. The FAHP score ranged from 0.145 (lowest priority) to 0.795 (highest priority), classifying sub-watersheds into ‘high’, ‘medium’ and ‘low’ classes occupying 10.76%, 27.23% and 62.01% of the total area, respectively. The compound parameter values ranged from 6.05 (highest priority) to 10.77 (lowest priority), and the ‘high’, ‘medium’ and ‘low’ classes occupied 31.84%, 16.49% and 51.67% of the total area, respectively. Common sub-watersheds identified as ‘high’ priority by both methods were SW14 and SW15, accounting for 10.76%, whereas under the ‘low’ priority class, SW1, SW8, SW9, SW11, SW12 and SW16 accounted for 42.66% of the total area. Consequently, eight sub-watersheds were found to be common in both prioritization methods corresponding to their respective priority classes. Through this investigation, the integration of GIS technology, morphometry and prioritization methods has proven to be indispensable in watershed management and soil conservation efforts. The findings further emphasize the urgent need for attention from decision-makers toward critical sub-watersheds.