Overtopping-Induced Failure of Non-Cohesive Homogeneous Fluvial Dikes: Effect of Dike Geometry on Breach Discharge and Widening

Laboratory experiments were conducted to assess the influence of dike geometry on the breaching of non-cohesive homogeneous fluvial dikes. Both the channel-side and floodplain-side dike slopes and the crest length were varied systematically. The time-evolution of the breach discharge and breach width was monitored. Dikes having a larger volume per unit width lead to a more gradual increase in breach discharge and in breach width during the first stage of breach expansion (i.e., phase of rapid erosion). In contrast, the later stage of gradual breach widening is less influenced by the dike geometry. The breach hydrographs were observed to follow three distinct patterns, which are explained based on the relative magnitude of two characteristic time scales and of a normalized form of the dike unit volume.