Study region: 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. Study focus: 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. New hydrological findings for the region: 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 similar to 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.