The Impact of Urbanisation on the Hydrological Responses of the Bouskoura Catchment : Analysis of Runoff Coefficient and Flood Flows from 2017 to 2030

Abstract Urbanisation has become a key driver of hydrological change, particularly in peri-urban catchments of semi-arid regions. This study investigates the impact of land use transformation on runoff dynamics in the Bouskoura watershed, a rapidly urbanizing area on the outskirts of Casablanca, Morocco. Using supervised classification of Sentinel imagery, land use changes between 2017 and 2021 were quantified, revealing a 30.08% increase in urban surfaces and a concurrent decline in vegetated and agricultural areas.To evaluate the hydrological consequences of this transformation, runoff was estimated using the SCS-CN method and simulated through the HEC-HMS model under uniform rainfall conditions for 2017, 2021, and a 2030 projection. The runoff coefficient increased from 69.11 in 2017 to 72.06 in 2021, while peak discharge rose from 28 m³/s to 42 m³/s. Projections for 2030 suggest a peak discharge of 92.9 m³/s, reflecting the expected rise in imperviousness due to ongoing urban expansion.Despite the absence of flow calibration data, the results provide a comparative analysis that demonstrates the sensitivity of runoff to land use change. This research offers a replicable framework for assessing urbanization-induced hydrological shifts in data-scarce environments and highlights the urgent need to integrate stormwater management into urban planning policies in North African cities.