Peak flood estimation under overtopping and piping conditions at Vahdat Dam, Kurdistan Iran

Estimation of maximum discharge and time of transfer dam break wave are among the main factors in provision of emergency action plan and safety assessment of dams. Most dam breaks begin with a breach in the body of the dam or flood overtopping. Estimation of maximum discharge for determining affected areas and also determination of hazards due to the dam break are essential issues. In this research, the dam break of Vahdat Dam located in Kurdistan, Iran, and in neighborhood of Sanandaj City was simulated by integrating ArcMap and HEC-RAS software and field observations. The necessary data was collected from the corresponding organizations. The Manning coefficient of the Gheshlagh River at downstream of the dam was estimated using the Manning coefficient relationships and field observations and measurements. The breach dimensions were determined using the conventional empirical relationships. The dam breaks in both overtopping and piping states were simulated. The maximum discharge values obtained from the modeling and empirical relationships were compared. The results indicated the substantial effect of selecting break types on the hydraulic characteristics of dam break wave in the river and downstream areas. While in the case of break due to the breach, selection of the methods for calculation of breach dimensions would affect the break and these relationships in various conditions would give different breach dimensions.