Effect of Dam Height on Breaching Due to Overtopping of Non-Cohesive Earthen Dams

The study of dam breach due to overtopping has become increasingly important because breaches have had devastating impacts on urban and rural communities. The ability to predict and understand breaching is critical for flood-damage mitigation, emergency planning and evacuation. Experiments on dam breaching due to overtopping were run on non-cohesive model embankments of heights varying between 10 cm and 45 cm. Experiments were performed in a 3-foot wide and 4-foot-tall flume in the Hydraulics Laboratory at the University of South Carolina. The dams were built in 5 cm lifts with equal compaction. Slopes equal to 3H:1V were then cut to create the final dam shape. A pump provided a constant discharge, and an overflow weir was used to maintain a constant water level in the upstream reservoir. A rectangular pilot channel of 2.5 cm in width and 1.2 cm in depth was used to initiate the breach over the center of the dam. Preliminary results show that both failure time and breach geometry are function of dam height. A noticeable increase in breach flow occurred earlier in experiments with smaller dam height. The increase in breach flow was associated with the occurrence of dam crest erosion. Interestingly, the final breach was narrower in experiments performed with higher dams.