Analysing and simulating dam breach events and the resulting floods is critical for differentiating and reducing impendences due to possibility failure of dams. Hydrological Engineering Centre (HEC-RAS) River Analysis System was used for developing dam failure model. HEC-GeoRAS was used to extract geometric information from a Digital Elevation Model (DEM) and then imported into HEC-RAS version (5.0.7).
The process of dam breach modelling is to analyse the downstream flooding risks of the dam by the simulating of possible failure of dam scenarios. The prediction of geometry for dams breach is important in studies of dam breach. Flood hydrograph characteristics that result from dam breach depend on breach geometry and time required for the breach forming. For investigating the effect of breach parameters on breach maximum outflows, five empirical equations are used in order to predict dam breach parameters by using HEC-RAS model. Hamrin dam was selected as a case study in this research. The dam has been checked for overtopping and piping failure modes by the use of two dimensional river analysis model HEC-RAS and for use in the model. The unsteady flow calculations performed in HEC-RAS.
For Hamrin dam, we used five empirical equations for predicting breach geometry and breach formation time. The equations used are Singh and Snorrason (1982), MacDonald and Langridge-Monopolis (1984), Bureau of Reclamation (USBR) (1988), Von Thun and Gillette (1990) and Froehlich (2008). Three water levels for each method were considered. Peak discharge value and time of peak discharge were analysed and discussed for each scenario. The results showed that Froehlich approach was most adequate empirical equation to estimate the breach parameters for Hamrin dam. Overtopping failure mode tends to provide higher peak discharge (61909.64