FLOOD02543

• County: Statewide
• Basin: Statewide
• Title: Emergency Action Planning Guidelines for Dams
• Date: 2/1/1985
• Prepared For: US
• Prepared By: FEMA
• Floodplain - Doc Type: Educational/Technical/Reference Information

actions internal and external to the facility be performed in isolation of
each other."

C. Scope. This document contains guidelines for preparing emergency action
plans for those dams which, if they were to fail, would be likely to cause
loss of life or extensive property. damage. Development of the flood plain
downstream from dams varies, therefore, the potential loss of life from each
dam failure is different. A greater level of detail should be used in the
preparation of emergency action plans when the potential for loss is large
than when it is small.

Emergency action plans generally contain six basic elements. The elements
are identification of emergency, preventive action, notification and
coordination, hazard area delineation, evacuation, and termination and
follow-up. All of these items are discussed. The dam owner is responsible
for much of the plan development; however, the impacted communities need to
prepare and implement the evacuation plan element. Coordination is essential
between the dam owner and communities involved as well as with appropriate
local, county, state, and federal entities.

The purposes of these guidelines are more likely to be achieved if methods
are readily available for predicting and detecting dam failures. Early
discovery of hazardous situations allows the initiation of efforts to prevent
or delay dam failure and provides additional time for issuing warnings to
flood plain occupants. Many lives may be saved when dam failure is predicted
or detected early in the failure process. Conversely, large numbers of lives
may be lost when a dam failure occurs without advance knowledge of the pending
failure. Although the importance and need for prediction/detection systems or
processes are identified, the development and presentation of such information
is beyond the scope of these guidelines.

D. Inundation Associated with Dam Failures and Large Releases

1. General. Information on flooded areas and warning times are
essential to the development of notification and evacuation plans. This
information may be obtained from evaluations of a postulated dam failure or
major flood and subsequent routing of the resulting flows downstream.

2. Critical Conditions. Several different assumptions could be made
regarding the appropriate condition prevailing at the time of a dam break. A
"fair weather" dam break is generally considered to have the most potential
for loss of life. Therefore, the "fair weather" dam break is selected as the
minimum condition to be used in these guidelines. The normal full pool (top
of flood control storage or other active storage, excluding surcharge) should
be the reservoir level assumed for the dam break flood. Failures at other
higher pool level situations such as a flood overtopping the dam should be
considered and should be used if they are critical in terms of potential loss
of life. This is particularly important for some mine tailings dams.

In addition to the failure condition, information regarding the inflow
design flood or other large flood should be included to depict both upstream
and downstream flood levels for the nonfailure condition. Generally, the
flood

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