GIS-integrated 2D HEC-RAS modeling approach for assessing dam-break floods and their socio-economic consequences in urban arid environment

Abstract

Frequent flash floods in arid regions threaten infrastructure and residents. Jeddah, Saudi Arabia, has experienced severe flooding, underscoring the need for improved forecasting and risk analysis. This study explores dam failure and flood mapping in Jeddah’s Al Tawfiq sub-basin to improve disaster prediction using HEC-RAS 2D, WMS, and GIS. WMS was used for watershed delineation, hydraulic data extraction, and model setup. HEC-RAS simulated a dam breach to generate flood extent, depth, and velocity maps. GIS-supported spatial data processing, visualization, and risk assessment by layering flood maps over infrastructure and populated areas. Six daily rainfall depths—30, 35.7, 42.2, 58.5, 72.3, and 133.3 mm—were used to simulate the breach. After a 30 mm rainfall event, the primary school and part of Al Tawfiq Cemetery were initially flooded to depths of 0–2 m. The flood affected the drain canal with depths of 2.1–7.8 m. The schools and gardens in the area experienced flooding of 2.1–7.8 m. The water depth ranged from 0 to 7.2 m in the power electrical station. Rainfalls of 30, 35.7, 42.2, 58.5, and 72.3 mm caused water depths of 7.9–13.4 m (51982.4 m²) and 13.5–20.7 m (125,751.5809 m²) in the same areas. During rainfall depths of 72.3 and 133.3 mm per day, flood depths reached 8.4–13.6 m and 12.9–20.7 m in the western region, increasing the risk to residential zones. The most affected facility was the electrical power station, which experienced the most flooding and damage at higher rainfall depths. Emergency planning, land-use control, and early warning systems benefit from identifying high-risk locations. The study shows that HEC-RAS, WMS, and GIS can manage flood risk in arid urban areas.