Resources by Topic

Resources by Topic: Risk Informed Decision-Making

Overview

Risk, as used in the dam safety community, can be generally defined as a measure of the likelihood and severity of adverse consequences. Dam Safety risk is computed for a variety of potential failure modes, typically considering failure as an uncontrolled release of the reservoir. The risk for a particular failure mode is computed as the product of the:

  • likelihood of a loading condition (static, seismic, hydrologic, mechanical, electrical);
  • response of some component of the dam to the load (likelihood of failure given the load); and
  • consequences of the dam’s response to the load (consequences of dam failure).

Total risk is the summation of risk from the identified potential failure modes. Risk is expressed in terms of life-safety and economic consequences on an annualized basis. The units of measure for dam safety risk are loss-of-life per year for life-safety and costs (dollars) per year for property damages and economic losses.

Risk-informed decision-making is the process of using information about risk to assist in decision-making with regard to a wide variety of dam safety activities. This would include decisions regarding actions such as: frequency of inspection; need for increased instrumentation; need for additional technical studies; assessment of how uncertainties affect the level of risk; sufficiency of evidence to support the need for remedial action; selection of a remedial action to address an identified deficiency; prioritization of projects or actions; and the sequence in which remedial actions are taken at a given dam or group of dams.

Quantification of risk through risk analyses is accomplished by individuals with experience in various fields such as geotechnical, hydrologic, hydraulic, structural, mechanical and electrical engineering, engineering geology, meteorology, seismicity, dam construction, project operations and other related fields as they pertain to a given potential failure mode at a specific dam. These are individuals who can provide information regarding the likelihood of a given loading condition (flood, earthquake, maximum reservoir levels, etc), or the process by which failures occur (sequence and likelihood of system responses) or the manner in which the dam and reservoir have been operated.

Decision-making is typically accomplished by individuals or groups with a broad range of technical and management experience in dam safety and project operations. Qualitative or quantitative information about dam safety risks are considered along with other project-specific information in deciding on a course of action. Risk-informed decision making can be conducted in a manner that seeks efficiency in balancing the costs of risk reduction with addressing the highest risks first.

Proficiencies

To be proficient in this area one first needs to have experience in one or more engineering or scientific disciplines that provide information about failure modes for dams and also understand the procedures used for computation of dam safety risk. In addition, it is desirable to have dam design, analysis, and construction experience as well as knowledge in dam operations. Experience or training in the following subject areas would be beneficial:

  • Procedures used for conducting Potential Failure Mode Analysis (PFMA)
  • Concepts and procedures used to estimate the likelihood of static, hydrologic or seismic loading conditions
  • Mechanisms by which failure occurs for various components of a dam and appurtenances
  • Use of event trees for computation of risk for individual potential failure modes and estimation of total risk
  • Engineering and societal perspectives on risk, risk tolerance and approaches to risk reduction

Classroom and Web-Based Training

Search the ASDSO Training Directory.

Guidelines and Suggested References

Some of the most highly recommended resources in this area are listed below. Additional resources are available through the ASDSO Bibliography. Suggested search terms: risk, decision-making.

Federal Emergency Management Agency

U.S. Army Corps of Engineers

  • Dam Safety Assurance Program [EP1110-2-1155], 1997, 47 pp.
  • Dam Safety Preparedness [EP 1110-2-13], 1996, 58 pp.
  • Reliability Analysis and Risk Assessment for Seepage and Slope Stability Failure Modes for Embankment Dams [ETL 1110-2-561] CECW-EW, 2006, 128 pp.
  • Andersen, Glen; Chouinard, Luc and Foltz, Stuart. REMR Management Systems - Flood Control Structures: Condition Rating Procedures for Earth and Rockfill Embankment Dams, U.S. Army Corps of Engineers, 1999, 106 pp.
  • Safety of dams - Policy and Procedure [ER 1110-2-1156], 2003, 168 pp.
  • Safety of dams - Policy and Procedure [ER 1110-2-1156], August 2011.

U.S. Bureau of Reclamation

  • Best Practices in Dam Safety Risk Analysis, Version 2.2, Denver, Colorado, April 2011.
  • Dam Safety Public Protection Guidelines, Dam Safety Office, Denver, Colorado, August 2011.
  • Dam Safety Public Protection Guidelines – Examples of Use, Dam Safety Office, Denver, Colorado, August 2011.
  • Rationale Used to Develop Reclamation’s Dam Safety Public Protection Guidelines, Dam Safety Office, Denver, Colorado, August 2011.
  • Graham, Wayne. A Procedure for Estimating Loss of Life Due to Dam Failure, DSO-99-06, U.S. Bureau of Reclamation, 1999, 46 pp.
  • Guidelines to Decision Analysis, ACER Technical Memorandum No. 7, Denver, 1986, 223 pp.
  • Bowles, David and Swain, Robert. A Framework for Characterizing Extreme Floods for Dam Safety Risk Assessment. Utah State University and U.S. Bureau of Reclamation, 1999, 76 pp.

Montana Department of Natural Resources and Conservation

American Society of Civil Engineers

  • Scott, G.A., "The Practical Application of Risk Analysis to Dam Safety," Proceedings, GeoRisk, Atlanta, GA, July 2011, pp. 129-168.
  • Singh, Vijay; Jain, Sharad and Tyagi, Aditya. Risk and Reliability Analysis: A Handbook for Civil and Environmental Engineers. American Society of Civil Engineers, 2007, 800 pp.

Association of State Dam Safety Officials

  • Scott, G.A., "Shedding Some Light on This Thing Called Risk Assessment, Part I – Risk Analysis Basics." The Journal of Dam Safety, V.8, n1, pp. 20-26, 2010.
  • Scott, G.A. and Fiedler, W.R., "Shedding Some Light on This Thing Called Risk Assessment, Part II – Example Risk Analysis." The Journal of Dam Safety, V.8, nIssue 3, pp. 8-19, 2010.
  • Von Thun, Lawrence; Bowles, David and McCann, Martin. Workshop on Risk Assessment, ASDSO Technical Seminar, Oct. 1999, 325 pp.

National Research Council

  • Safety of Dams Flood and Earthquake Criteria, Washington, D.C.: National Academy Press, 1985, 292 pp. (Available online, http://www.nap.edu).

U.S. Committee on Large Dams

  • Eighteenth Annual USCOLD Lecture: Managing the Risks of Dam Project Development, Safety and Operation, 1998.

Research

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