Modeling dam-breach-induced flash flooding: a case study of the 2018 Wadi Al Lith event, Saudi Arabia

ABSTRACT The graphical abstract illustrates the integrated modeling framework used for the 2018 Wadi Al Lith dam-breach flood. This model merges hydrological, hydraulic, and topographic data to simulate flood dynamics and support early warning systems in arid regions. Extreme rainfall upstream of Wadi Al Lith in Saudi Arabia (SA) led to a dam failure, flash floods, and infrastructure damage on 23 November 2018. This study predicts flood damage resulting from the failure of Al Lith Dam and proposes environmental mitigation strategies. Using remote sensing (RS), geographic information systems (GIS), digital elevation models (DEM), and rainfall data, hydrodynamic models such as WMS, HEC–HMS, and HEC–RAS 2D simulated the breach and wave movement. The catchment area covered 3029 km2 and had a perimeter of 442 km. Peak discharges were estimated for 1- and 50-year return periods. Most flooding impacted agricultural zones within 4 hours, with depths up to 3 m; highways and bridges within 8 hours, reaching depths of up to 6 m; and parts of Al Lith city after 12 hours. Water velocities ranged from 0 to 1.5 m/sec, prolonging flood effects. Some parts of Al Lith flooded when the dam breach modelling was omitted. Nakhl An Nilah and Nada Pebble basins are located downstream of the dam. Two new dams are proposed north and south of the Al Lith Dam, with capacities of 182 million and 44.1 thousand m3. Ghomygah village remained unaffected; urbanization is recommended.