Spatiotemporal sensitivity of flood dynamics to desert urbanization in Al Ain, UAE

Al Ain, the primary inland urban center of the United Arab Emirates, lies on the leeward pediment of the northern Oman Mountains and is drained by ephemeral wadi systems prone to flooding during intense convective storms. This study examines how land-use/land-cover (LULC) change from 1987 to 2023 has altered basin-scale flood response in Al Ain using Landsat-derived LULC maps and a fully distributed, physically based GSSHA hydrologic model. Five historical storm events, including the extreme April 2024 event, were simulated to examine flood responses under moderate and extreme storm conditions. Between 1987 and 2023, impervious surface area increased by approximately 274 %, while irrigated and managed vegetation expanded mainly in downstream and peri-urban areas. Under low-to-moderate storm conditions, urbanization increased runoff volumes and peak discharge by ∼25–78 %, shortened response times, and increased maximum flood depths, indicating strong sensitivity to land-surface modification. During the extreme April 2024 event, runoff generation was dominated by widespread infiltration-excess (Hortonian) overland flow, substantially reducing sensitivity to LULC differences and revealing a nonlinear threshold in flood response. Flood hazards are increasingly concentrated within densely developed urban areas, while vegetated zones enhance localized infiltration but do not offset catchment-scale runoff increases. These findings highlight the need for storm-magnitude-aware flood assessment and distributed, infiltration-focused mitigation strategies in rapidly urbanizing desert cities. • A 37-year Landsat record shows 274 % urban growth in Al Ain, UAE. • GSSHA modeling identifies nonlinear, threshold-driven runoff behavior. • Urbanization increased runoff volume and peak discharge by up to 78 %. • Extreme rainfall generated Hortonian flow, reducing land-cover sensitivity. • Nature-based measures could cut runoff by 25–50 % in arid urban environments.