FLOOD10196

• County: Statewide
• Community: State of Colorado
• Basin: Statewide
• Title: National Dam Safety Program
• Date: 4/1/1986
• Prepared By: FEMA
• Floodplain - Doc Type: Educational/Technical/Reference Information

2. Costs of failure; and

3. Costs of preventing failure.

Use of risk analysis has been advocated in engineering for
dams, especially in areas such as determining spillway capacity
and design for earthquake resistance. since the magnitudes of
future floods or earthquakes to which a dam will be exposed in
its service life are largely indeterminate, past and current
design decisions involving these and similar indeterminate
loadings are based on accepted, albeit somewhat arbitrary,
standards. Risk analysis has been advocated as a rational
approach to such problems to avoid potentially costly over-
designs or underdesigns in dams. The most significant
deterrent to use of the risk analysis approach has been the
difficulty of assigning probabilities to the phenomena involved
in dam failures.

Use of risk analysis techniques was considered in a 1985
study entitled Safety of Dams - Flood and Earthquake criteria
(Reference 10), sponsored by the Department of the Army and
the Department of the Interior. As noted in Appendix 6, the
Federal Emergency Management Agency also has sponsored research
and training in application of risk analysis to dams. other
research efforts in use of risk analysis have been reported by
the Corps of Engineers and the Bureau of Reclamation.

About half of the Federal agency reports indicate that
rough consideration of relative risks is part of the process of
establishing agency priorities for activities such as dam
inspections and rehabilitation work. The Soil Conservation
service reports that considerations of risk are part of
current studies of dam safety standards. The Bureau of
Reclamation has conducted training workshops on risk analysis
techniques for its staff.

Dam Failures and Other Safetv-related Incidents

Table 3 summarizes the dam failures and other serious dam
safety-related incidents reported by the Federal agencies as
occurring in the period from January 1980 through September
1985. In a few instances, the listing of individual incidents
in specific columns of Table 3 may be in error, as the Federal
agency reports did not indicate clearly in all cases whether
the dam involved actually failed or whether the dam was in
Federal or non-Federal ownership. As the Federal agencies
only reported incidents at non-Federal dams in which the
respective agencies had some interests, it is reasonable to
assume that there were more -- probably many more -- failures
and dam safety-related incidents at non-Federal dams that are
not listed on Table 3.

Chapter 3 - page 26