Flash flood forecasting is indispensable to construct efficient warning and mitigation of the increasingthreat of flash floods in wadi systems. Flash floods modeling in arid region is hindered by the lack ofappropriate hydrological models and data availability. Rainfall-Runoff-Inundation (RRI) model is appliedin Wadi Samail as a case study for the most extreme flash flood events in Oman (1,000 year return period).Detailed sensitivity analysis were conducted for RRI model parameters indicating that the channel andhillslope roughness coefficients are the most significant parameters followed by the soil characteristicsparameters such as soil depth, porosity and hydraulic conductivity. The most severe tropical cyclone in therecent history in Oman, Gonu-2007 and Phet-2010 were used to calibrate and validate the hydrologicalmodel. The results and the statistical analysis indicating that RRI model could efficiently simulate the extremeflash flood events in the arid wadi system. Where for model calibration, Nash-Sutcliffe efficiency(NSE) and Percent bias (PBIAS) indices equal to 0.93 and -14.3, respectively, and for model validation NSEand PBIAS equal to 0.86 and -12.0, respectively. Further improvements in RRI model is recommended toinclude the transmission losses and groundwater processes for better representation of the wadi system.
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