Fluvio-geomorphologic Analysis of Lower Ajoy River, West Bengal, India

The lower Basin of the Ajoy River confronts regular floods resulting in regular erosion and breeches, mostly its right embankment, adding to its meandering downstream of Illambazar. The erosion is intense after the Kunur tributary joins the Ajoy River. Bank erosion, breeching, and flash flood inundation create havoc in Birbhum and Bardhhaman (Purva) districts before joining the River Bhagirath at Katwa. Literature is meagre about the causes and remedial measures for the splash floods.

The present research, various published studies, physical collection of in-situ spatial information and (GIS/RS)-based assessment and ERDAS-based mapping of the lower flood-delta of the Ajoy River have been tried through slope map, land use (LU) AND Land cover (LC) map. The river’s seasonal water level (1991-2023) at Gheopara gauge station (Least G&D stations at lower reaches) is considered. The JAVA script uses Landsat images from Google’s cloud platform and Q-GIS software used for finding the “Normalized Differentiated Moisture Index” (NDMI), and “Normalized Difference Vegetation Index” (NDVI) for the tail reaches of the Ajoy River. The novel modified BEHI (The modified Bank Erosion Hazard Index) model was applied to the Ajoy River Bank’s erodibility probabilities calculation.

The analysis results infer that the frequency and power of floods have surged with climate change (CC), mining, urbanization, deforestation, erroneous tillage, and anthropogenic interventions. Multidimensional structural judicious approaches by calculating bank erosion potentialities can ameliorate the increasing bank stability of the Ajoy tributary by preserving SDG 6 and SDG 13 to 15.