Date of Award
Open Access Thesis
Civil and Environmental Engineering
Dr. Enrica Viparelli
The National Inventory of Dams reports 74,400 earthen dams in the United States in 2021, of these dams approximately 27% are considered at high or significant hazard risk, that is dam failure will cause widespread damage and loss of lives. The most frequent cause of dam failure is breaching caused by overtopping. Accurate predictions of breach evolution are thus crucial to determine flood hydrographs for the safety of communities and properties at risk. Laboratory experiments were conducted on non-cohesive, compacted embankments to understand the role of dam height and sediment grain size on breaching caused by overtopping. Dam heights varied from 10 cm to 45 cm. Model structures were built with fine sand or with a mixture of fine sand and silt. Experiments showed that increasing dam height increases peak discharge. The presence of silt in model embankment material, on the contrary, lowers peak discharge and makes failure longer. In sand dams, sediment deposition on the downstream face becomes important as dam height increases. This deposition reduces incision rate of the breach channel delaying time to peak and rapid channel widening. In all embankments, breach evolution was gradual until erosion of the breach channel reached the reservoir. Throughout the experiment, bank failure caused gradual widening of the breach channel. In presence of silt, no sediment deposition occurred on the downstream face and time to peak increased with dam height because upstream migrating erosional waves formed in the breach channel and the time for these waves to reach the reservoir increased with dam height. Breach channel widening associated with bank failure is practically non-existent until peak discharge is reached, then sudden widening caused by major failures occurs. Overall, breach width decreases with an increase in silt content.
O'Donal, H.(2023). Impact of Dam Height and Grain Size Distribution on Breaching of Non-cohesive Dams Due to Overtopping. (Master's thesis). Retrieved from https://scholarcommons.sc.edu/etd/7472