Risk Management: Challenges and Practice for US Dam and Levee Safety

Abstract

One of the earliest research efforts on internal erosion was funded by the Government of India in 1895 at Thomason Civil Engineering College, Roorkee (Clibborn, 1902). The research was an effort to understand the 1885 failure of the Khanki Weir and use this information to refine design guidance. This led to early improvements in the analysis and design of defensive measures to prevent piping failures of dams, as well as enabling the prediction of the failure of Narora Weir in 1898. Knowledge of potential design flaws has grown significantly through research and, unfortunately, dam failures. The United States has an aging dam infrastructure, with most dams now beyond their anticipated 50-year economic life. Many of the early dams were designed and constructed prior to adequate knowledge of hydrology, liquefaction, backward erosion piping, dispersive soils, and concentrated leak erosion. While modern dam designs utilize defensive measures to address these concerns, many older dams do not. Dam and levee safety practice in the United States is currently undergoing an evolutionary phase in which risk management practices are seeing wider application in order to help prioritize dam rehabilitation work. The US Federal Energy Regulatory Commission, US Bureau of Reclamation, and the US Army Corps of Engineers are currently implementing risk-informed methodologies in their dam safety programs, and the US Army Corps of Engineers is currently extending this methodology to their navigation and levee programs. Some key challenges include needed refinements on the topics of: internal erosion evaluation and prediction, hydraulic loading from extreme events and climate change, site characterization uncertainties, combining and portraying risks for complex systems, and seismic load and post-seismic response predictions. While Col. Clibborn helped dam engineers to begin to understand the mechanics of internal erosion in 1895 and its implications to dam design, much work remains to be completed. Future studies will improve risk assessments resulting in higher confidence and improved risk-informed decisions regarding prioritization of dam rehabilitations.