Stability of Rockfill in End-Dump River Closures

One method of river closure is by end-dumping loose rockfill from one or both banks progressively into the flow. Determination of stable closure material size by correlation with either mean velocity through the gap or velocity near the boundary as done in the past is not realistic. In this study the closure material stability is defined numerically by a parameter efficiency of closure material, which denotes the ratio of the volume of the material remaining in the body of the dam to the volume dumped at any stage. Analysis of all the relevant parameters indicated the Froude number of approach flow, the contraction ratio, the ratio of the closure material size to the approach flow depth and the efficiency of closure material to be the essential inter-related nondimensional variables describing stability. The functional relationship was established by the results of a laboratory study and practical design curves to directly determine the stable size of closure material, are presented.