Parametric Breach Model Evaluation from Laboratory Rockfill Dam Models under Overtopping Conditions

Rockfill dams are a common dam type, but breach development in these dams is not very well understood, particularly rockfill dams with placed or dumped riprap protections on the crest and downstream slope. In this paper, we look at several experimental setups investigating the overtopping of rockfill dam models with and without riprap protections and how these experimental results compare with existing empirical models for breach development in embankment dams. We describe the model setups, data acquisition, and data analysis as well as the comparison with existing empirical equations for breach development, focusing on the following parameters: breach width, breach formation time, and peak outflow. The discussion brings to light how the parametric breach models can predict breach development in rockfill dam models. It also highlights how the existing models are wholly unsuited to predict breach development in protected dam models. Breach initiation and development in protected dams differs so much from unprotected dams that new models are needed. Such models could integrate new parameters that describe the resistance against erosion the crest and slope protection provides, as well as the sudden breach development that ensues once the protection fails.