Risk Assessment

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"Risk assessment is the process of considering the quantitative or qualitative estimated risk of the existing dam or project, along with all other factors related to a safety decision. These factors can include the dam safety case, social/economic impacts, environmental impacts, constructability, and potential to do harm. The risk assessment is conducted to determine a recommended course of action (which may involve considering a range of options) for mitigating or accepting the risks related to a specific dam or project or with regard to a specific dam safety issue or operational concern on that project."

"Typically the risk assessment and proposed recommendations are initially developed by the risk analysis team and then reviewed, and possibly revised, by a technically qualified and experienced team, rather than a single individual. This specialized team can discern the relative criticality, the measure of concern, and the type and degree of remedial action needed to address the issue. When there is justification to take dam safety actions, a suite of options should be identified, and the costs and potential benefits of each option should be developed and presented. The final decision to adopt any recommended dam safety actions is made by the authorized decision makers within the organization. The most obvious and direct factors that enter into the assessment are the results of a risk analysis. These results may come in the form of quantitative/numeric results or qualitative statements that indicate the measure of concern relative to public safety."

"Quantitative results provide three measures related to risk. They are:

1. "Likelihood of occurrence of a failure or adverse consequence in terms of annual probability
2. "Estimated population at risk and/or life loss given failure or adverse consequence presented as the total estimated loss for a given annual probability of failure (often plotted or graphed), or the product of those two values which is called the annualized life loss
3. "The economic damages (e.g., downstream damages, cost to rebuild facilities, loss of operational revenue, regional social/economic damages, environmental damages, etc.). Again, these can be given or plotted as the lost economic value versus the annual probability of occurrence or as an annualized cost"

"However, there are many factors that may be included in a dam safety case and can be considered in the decision recommendation. They include:

• "The risk analysis input for the dam safety case
• "The design and construction of the dam, including defensive design features
• "The past and future performance monitoring of the dam
• "Environmental considerations
• "Public perception and public input
• "Regional, social, and economic considerations
• "Ease, difficulty, and practicality of remediation
• "Potential to do harm as a result of carrying out remediation
• "Uncertainty about the results and the success of the remediation"

Best Practices Resources

Federal Guidelines for Dam Safety Risk Management (FEMA P-1025), FEMA

Dam and Levee Safety: Using Risk-Informed Decision Making, USACE

Citations:

Revision ID: 7837
Revision Date: 03/28/2024