Olsen, Christopher
Submitted to the University of New Hampshire in Partial Fulfillment of the Requirements for the Degree of Master of Science in Hydrology.
THESIS ABSTRACT:
Impounded sediment reduces reservoir storage capacity, which adversely affects dam functionality. For example, reduced capacity limits the ability of flood control dams to mitigate flood peaks, water supply dams to meet demands, and hydropower dams to produce adequate electricity during low flows. Larger sediment volumes also increase the risk of dam failure and increase the logistical complexity of dam removal, an increasingly popular ecosystem restoration method. A model to predict the impounded sediment volume would be useful for decision makers in a watershed or state that need to allocate limited resources to multiple dams. A cross-site comparison among 34 dams was conducted to examine how the volume of impounded sediment was related to sediment supply, transport, and settling. Proxies for sediment supply, transport, and settling were obtained from published datasets and remote sensing. Most methods used to remotely sense proxies were derived from previously published research, but this thesis also developed a novel remote sensing method for locating the position riverbanks. This novel method was found to accurately predict the location of riverbanks in several different river morphologies. Regression analysis was used to quantify relationships between the impounded sediment volume and sediment supply, transport, and settling proxies. Impoundment attributes such as the impoundment surface area, impoundment aspect ratio and dam age were the best predictors of the impounded sediment volume.