Abstract
This study used a simulation methodology for dam break analysis and flood simulation in an urbanized arid region, namely Um Al-Khair dam in Jeddah, Saudi Arabia. The analysis was performed using the 2011 rainfall storm of 111 mm and 281 min duration. The results show that the rainfall depth corresponds to a return period between 50 and 100 years. The hydrograph resulting from this storm was estimated using a rainfall-runoff model. The hydrograph was found to fall in between 100- and 200-years return period. This confirms that it is not necessarily to have the same return period for both rainfall and its corresponding flood due to the nonlinearity of the rainfall-runoff process. The dam breach parameters and the inflow hydrograph were used to model the flood propagation due to Um Al-Khair dam breach using HEC-RAS-2D software. A comparison between the modeled and observed water depths showed a relatively reasonable correlation coefficient of 0.57 and the RMSE of the water depth is 0.45 m, which are acceptable in such studies under the scarcity of accurate field measurements.