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

Glossary

For the purpose of these guidelines the following definitions apply.

CONSEQUENCES. Potential loss of life or property damage downstream of a dam
caused by floodwaters released at the dam or by waters released by partial or
complete failure of dam. Includes effects of land slides upstream of the dam
on property located around the reservoir.

DAM OR PROJECT. Any artificial barrier, including appurtenant works, which
impounds or diverts water, and which (1) is twenty-fIve feet or more in height
from the natural bed of the stream or watercourse measured at the downstream
toe of the barrier or from the lowest elevation of the outside limit of the
barrier if it is not across a stream channel or watercourse, to the maximum
water storage elevation or (2) has an impounding capacity at maximum water
storage elevation of fifty acre-feet or more. Definition does not apply to
any such barrier which is not in excess of six feet in height regardless of
storage capacity, or which has a storage capacity at maximum water storage
elevation not in excess of fifteen acre-feet regardless of height. This lower
size limitation should be waived if there is significant downstream
development.

DAM FAILURE. Catastrophic type of failure characterized by the sudden, rapid,
and uncontrolled release of impounded water. It is recognized that there are
lesser degrees of failure and that any malfunction or abnormality outside the
design assumptions and parameters which adversely affect a dam's primary
function of impounding water is properly considered a failure. Such lesser
degrees of failure can progressively lead to or heighten the risk of a
catastrophic failure. They are, however, normally amenable to corrective
action.

DAM FAILURE HYDROGRAPH. A flood hydrograph resulting from a dam breach at a
specific location downstream from the dam.

EMERGENCY. A condition of serious nature which develops unexpectedly and
endangers the structural integrity of a dam or endangers downstream property
and human life and requires immediate action.

EMERGENCY ACTION PLAN. Formal plan of procedures to alleviate risk during
construction of or after completion of a dam, or to reduce the consequences if
conditions develop in which dam failure is likely or unpreventable.

FLOOD HYDROGRAPH. A graph showing, for a given point on a stream, the
discharge, height or other characteristic of a flood with respect to time.

FLOOD ROUTING. A process of determining progressively over time the amplitude
of a flood wave as it moves past a dam or downstream to successive points
along a river or stream.

FREEBOARD. Vertical distance between a specified stillwater surface elevation
and the top of the dam, without camber.

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