Assessing the risks posed by the climate-induced failure of aging dams in the United States

Abstract:

The flood retention capacity of dams and levees has the risk of being overwhelmed by the increased frequency and intensity of floods. This combined with reduced storage due to sediment buildup, structural aging, poor maintenance, and faulty design, increases the probability of dam and levee failure. Further, development in floodplains increases the subsequent impact on critical infrastructure and populations that are downstream.

The United States has an inventory of more than 90,000 aging dams, with a median age of nearly 60 years. Yet, the potential risk of failure of dams is not established. Neither is the potential impact of the failure in terms of the value of the loss of services provided by the dam, or the downstream impacts on asset, population and reconstruction needs, or the cascading impact across the national and regional economy. Our research represents the first effort to develop an approach in this direction. We focus primarily on identifying methods for the rapid quantification of the time-dependent trigger probability for dam failure, and of the critical infrastructure that would be impacted if the dam fails.

Using dams in the Cumberland River Basin as a pilot, we show the application of the framework to quantify the causal network of the climate and age-induced changing risk of dam failures, and prioritize different dams or regions in terms of potential financial impact. In our case study, we found that there is an increasing trend in the number of events that could lead to failure by overtopping and that sedimentation further increases that probability. We found that current dam hazard classifications do not give visibility to the different types of hazards that each of them poses. All the dams were classified as High Hazard, but the financial impacts of the failure of each of them were strikingly different. This study provides the foundation for a comprehensive national risk estimation and prioritization effort for financial and other mitigation actions.