Morphometric characterization and erosion assessment of gullies in the lateritic badlands of Eastern India using ALOS AW3D30 DEM and topographic indices

The present geomorphic study analyzes the morphometric anomalies of the lateritic badlands (West Bengal, India) to understand the erosion intensity, triggering factors and landscape evolution using the ALOS AW3D30 DEM and quantitative techniques of various hydro-geomorphic processes (viz., basin morphometry, rainfall-runoff simulation, geomorphic threshold, erosion indices, sediment yield, SPI, and STI etc.). The GIS-based analysis reflects that there is the requitement of minimum drainage area (i.e. 55.71–349.01 m2) to maintain one metre of gully channel in the basins which have the network density of 2.86–13.76 km km−2. The critical slope (i.e. geomorphic threshold) of badland terrain varies from 0.0222 to 0.0407 metre metre−1, having dominance of overland flow erosion to initiate gully heads. The basin-wise SCS-CN and USLE coupling estimates that within the daily rainfall range of 11.41–66.41 mm day−1, the potential sediment yield of gully basins varies from 2.15 to 9.10 t ha−1. The SL index (i.e. 0.81–47.32 m) diagram reflects the beats of gully energy profile due to stream erosion enhancement, slope steepness, resistance of underlying lithologies and active tectonics. Hypsometric integral values of the gully basins, ranging from 0.4 to 0.6, emphasize a low entropy-based fluvial system and development of mature-youthful landform stage. The evolutionary stages of badlands are explained here by the connectivity model and hillslope – gully – river coupling system, showing a quasi-equilibrium to complex stage of landscape development at present.