GIS-Based Multi-Criteria Flood Hazard Assessment in a Mountainous Basin: A Study of the Melamchi River, Nepal
DOI:
https://doi.org/10.64862/Keywords:
Hydrogeomorphology, Hydrology, Risk governanceAbstract
Floods in steep Himalayan basins are intensified by monsoonal extremes, rapid terrain responses, and active tectonics. The vulnerability is more exacerbated by expanding infrastructure in the region. The study was conducted in Melamchi River Basin to quantify a flood hazard map using a GIS-based multi-criteria decision analysis (MCDA) with the Analytical Hierarchy Process (AHP). Ten parameters (elevation, slope, curvature, precipitation, land use/land cover, soil type, distance to roads, distance to rivers, NDVI, and Topographic Wetness Index (TWI)) to develop criteria for hazard modeling. The inputs for the data were extracted from shuttle radar topographic mission (SRTM), Landsat 8, FAO Soils Portal, Regional Database of ICIMOD, and Department of Hydrology and Meteorology. AHP pairwise comparisons set consistent weights (Consistency Ratio = 0.0835): precipitation (19.04%) dominated, followed by TWI (15.38%), distance to rivers (15.12%), distance to roads (13.97%), slope (9.83%), elevation (8.26%), NDVI (5.99%), LULC (5.89%), soil (3.91%), and curvature (2.61%). The composite Flood Hazard Index (FHI) delineated five classes: very high (14%), high (24%), moderate (26%), low (22%), and very low (14%). The high and very high zones are concentrated along the river corridors and infrastructure-dense valleys in the central and southeastern sectors, reflecting a combined effect of orographic rainfall, convergent topography (TWI), and drainage disruption near roads. Validation against the June 2021 flood impact shows strong agreement, confirming that model captures the basin’s principal flood-generating mechanisms. The thus generated map provides an operational basis for preparedness and land-use control, including river corridor setbacks, hydrologically sound road design, targeted vegetation restoration in low NDVI area, and densely co-located hydrometeorological monitoring stations. The approach is transparent, reproducible, and transferable to similar Himalayan catchments.
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