Transient Hydraulic Simulation of Breached Earth Dams

A conceptual method to alleviate flood damages due to overtopping failures of future small earthfill dams is the incorporation of a relatively thin erosion retarding layer within the dam. This paper investigates the potential reduction in the reservoir release due to the proposed erosion retarding layer. The paper provides a method for the determination of an optimal location of the layer so as to minimize the maximum possible reservoir release due to a gradually breached earth dam. The transient reservoir flow is simulated by a numerical model, based upon the solution of the one-dimensional St. Venant unsteady open-channel flow equations. These equations are solved by the method of characteristics, with appropriate boundary conditions incorporated into the solution procedure. The numerical simulation model is used to determine the reduction in reservoir release due to a single retarding layer and its optimal location for a wide range of pertinent geometric, hydraulic and dynamic parameters.