THRESHOLD SENSITIVITY AND OUTLET VERIFICATION IN DEM-DERIVED DRAINAGE EXTRACTION: A DIGITAL MAPPING FROM KHOBRAGADI RIVER CATCHMENT OF PENINSULAR INDIA

Abstract

A multiscale geospatial assessment was undertaken for the Bandia, Khobragadi, Kathani, Sati and Gadhavi river systems in Gondia and Gadchiroli districts, eastern Maharashtra. Regional drainage context was established from HydroBASINS, MERIT Hydro, OpenStreetMap and a drainage network derived from 30 m NASADEM data. Flow-accumulation thresholds of 1,000, 2,500, 5,000 and 10,000 cells were tested, and a 5,000-cell threshold was retained as a study-specific analytical compromise. The Khobragadi watershed was validated as the quantitative pilot and was characterized by an area of 1,833.608 km², a perimeter of 408.676 km, 749.814 km of extracted streams and a drainage density of 0.409 km km⁻². Fifth-order organization was reached, and 49.0% of mapped stream length was represented by first-order segments. Long-term JRC data indicated that 95.6% of historically detected water was non-permanent or seasonal. For 2025, a 4.66-fold post-monsoon expansion in Sentinel-2-derived surface-water extent was identified. Strong outlet sensitivity was demonstrated by the rejected Sati delineations. Regional mapping was therefore found to support river-system characterization, whereas locally verified outlets were required before basin-specific morphometry could be reported.