WinDAM, A Dam Safety Engineering Tool for Breach and Non-Breach Flood Events

摘要

Stories of catastrophic floods like those created by major Hurricanes Harvey, Irma, and Maria or stalled weather systems over states like North Carolina, South Carolina. Oklahoma, and Colorado have dominated headline news in recent years. In some cases, dam failures or incidents occurred due to embankment overtopping or internal erosion; however, the majority of dams performed as intended by releasing water through control systems like the principal and auxiliary spillways. To prepare for these types of events, agencies and engineers have developed emergency action plans to assist city planners, emergency managers, and the dam safety community. These plans typically have a flood inundation map to assist these planners and managers in determining the need for evacuations should a dam failure occur. However, more often than not, a dam failure does not occur. Yet, through proper operation of the dam such as spillway activation flooding upstream or downstream of the dam may occur regardless. While not intended in some cases, embankment overtopping or an internal erosion incident may induce flooding without breaching the structure. In these non-breach situations, city planners and emergency managers find themselves unprepared for these events. Scientists at the USDA-ARS Hydraulic Engineering Research Unit have partnered with the USDA-NRCS and Kansas State University to develop software, WinDAM (i.e. Windows Dam Analysis Modules), for predicting embankment erosion due to overtopping and/or internal erosion. Engineers and other practitioners may use the software to evaluate the potential for breach associated with overtopping or internal erosion as well as to route floods through the reservoir when breach does not occur. Features of the software include: 1) the ability to route the flow through multiple spillways including computing the rating for multiple vegetated auxiliary spillways and some standard principal spillways, 2) the ability to route flow over the top of the dam with the elevation of the dam allowed to vary from point to point and to compute the rating for a vegetated dam crest, and 3) the ability to compute draw down times and discharges with or without inflow to the reservoir. The software provides the outflow hydrograph for practitioners to examine the impact that breach and non-breach events may have in relationship to the dam. The presentation will provide information to the dam safety community, including engineers, city planners, emergency managers, and zoning regulators, on the use of WinDAM for both breach and non-breach analysis. The presentation will focus on non-breach flooding events that may occur during normal dam operation or in instances where overtopping or internal erosion may not result in a breach of the embankment.