2008 – An overview of risk assessment tools for US Army Corps of Engineers dams

David M Schaaf, Jeffrey A Schaefer, Rick W Schultz, Jason T Needham

Abstract: As one of the main federal agencies with responsibility to build, operate, and maintain large dams in the United States, the US Army Corps of Engineers (USACE) is developing a risk based framework to better manage their portfolio of 600+ dams in terms of risk management and prioritization of funding. A key element to this effort is the development of risk-based analytical tools to evaluate primary features for applicable failure modes. These are used in conjunction with loading and consequence modules to assess the overall risk associated with the dam in terms of lives and economic damages. The focus of this paper is on the engineering analysis modules used to generate fragility curves for dam features.

The analysis modules are broken into three main categories by engineering discipline: geotechnical, structural, and mechanical/electrical. The risk based assessment tools associated with geotechnical failure modes include Seepage & Piping, Embankment Stability, Seismic Performance, and Erosion of Unlined Spillways. The structural assessment tools include Concrete Monolith Stability, Spillway Gates, Scour of Concrete Lined Spillways, Spillway Training Wall Stability, Performance of Pipes through Dams, Hydropower Superstructures and Intake Towers. The mechanical and electrical are primarily focused on the performance of machinery used to operate dam gates.

This paper gives a broad overview of the main characteristics and methods used for each of these analysis tools. Some of the modules use historical performance to establish failure rates, while others are more analytically based. The context of each within the framework of the overall risk assessment effort of USACE dams is covered.

Keywords: risk based analytical tools, fragility curves, risk assessment, US. Army Corps of Engineers, portfolio, dams.