Hydrological modelling of land use land cover change effects on urban stormwater runoff in Hyderabad, Pakistan for 2017, 2021, and 2024

Pakistan is highly vulnerable to climate change, which points to the need for resilient urban infrastructure and effective stormwater management. This study investigates changes in land use and land cover (LULC) and urban stormwater runoff in Qasimabad, Hyderabad, Pakistan. LULC analysis was conducted with ArcGIS Pro 3.1.5, while hydrological simulation used HEC-HMS 4.11. Changes in LULC were assessed for 2017, 2021, and 2024; hydrological characteristics were examined through flow direction analysis and sub-basin modelling. Across the study period, the spatial distribution of built-up areas, vegetation, water bodies, and bare land changed substantially. Built-up land made up 64.3% of the classified area in 2017. That share was 36.8% in 2021 and 46.2% in 2024, reflecting changes in the mapped land-cover extent alongside continued urban development. Over the same period, population density rose from 8,708 persons per km² in 2017 to 9,963 persons per km² in 2024. Using the HEC-HMS model, seven sub-basins were identified, and peak discharge, runoff timing, and flow characteristics were quantified across the drainage network. When LULC, flow direction, and hydrological modelling were considered together, the analysis showed where runoff was concentrated and where drainage constraints might occur, especially in densely developed areas. These findings can guide urban planners and water resource managers in planning targeted stormwater drainage, protecting natural drainage pathways, and managing flood risk in rapidly developing urban areas.