Urban flooding is a recurring threat in the semi-arid cities of northeastern Morocco, where urbanisation of floodplains coincides with short, intense rainfall. This study assesses the flood hazard of the Tirakaa wadi in Nador and the performance of two mitigation measures—upstream retention basins and targeted reforestation—considered separately and in combination. The 7.42 km² catchment was represented through rainfall-frequency analysis, a local intensity–duration–frequency (IDF) relationship, event-based HEC-HMS modelling with the SCS Curve Number method under average antecedent moisture conditions (AMC II; CN-II), and two-dimensional hydraulic simulation in Iber. The hourly intensity observed on 10 October 2025 (58.2 mm/h) was compared post hoc with the T100 one-hour IDF intensity (59.6 mm/h) as a single-event plausibility check, rather than as formal validation. For the T100 design-storm simulation, reforestation reduced the outlet peak discharge by 27%, the total inundated area by 2.6%, and the high-hazard area by 12.0%. On a common mapped domain, retention and the combined configuration reduced total inundated area by 5.4% and 10.2%, and high-hazard area by 7.5% and 26.3%, respectively. A complementary footprint-exclusion indicator, reported relative to the full-domain baseline, gives reductions of 21.2% and 26.0% for total inundation and 36.5% and 55.3% for high hazard when the 87,744 m² intentional-storage footprint is omitted from the basin-containing configurations. The common-domain metric provides the like-for-like comparison.