FLOOD09216

• County: Statewide
• Community: State of Colorado
• Basin: Statewide
• Title: Glossary of Terms for Dam Safety
• Date: 2/1/1988
• Prepared By: Interagency Committee on Dam Safety
• Floodplain - Doc Type: Educational/Technical/Reference Information

Heel. The junction of the upstream face of a gravity or arch dam with the
ground surface. For an embankment dam the junction is referred to as the
upstream toe of the dam.

Height, Above ground. The maximum height from natural ground surface to the
top of a dam.

Height, Hydraulic. The vertical difference between the maximum design water
level and the lowest point in the original streambed.

Height, Structural. The vertical distance between the lowest point of the
excavated foundation to the top of the dam.

Hydrograph, Breach or Dam Failure. A flood hydrograph resulting from a dam
breach.

Hydrograph, Flood. A graphical representation of the flood discharge with
respect to time for a particular point on a stream or river.

Hydrograph, Unit. A hydrograph with a volume of one inch of runoff resulting
from a storm of a specified duration and areal distribution. Hydrographs from
other storms of the same duration and distribution are assumed to have the
same time base but with ordinates of flow in proportion to the runoff volumes.

Hypocenter. The point or focus within the earth which is the center of an
earthquake and the origin of its elastic waves.

Instrumentation. An arrangement of devices installed into or near dams (i.e.,
piezometers, inclinometer, strain gages, measurement points, etc.) which
provide for measurements that can be used to evaluate the struct~ral behavior
and performance parameters of the structure.

Intake. Any structure in a reservoir, dam or river through which water can be
discharged.

Inundation map. A map delineating the area that would be flooded by a
particular flood event.

Length of dam. The length along the top of the dam. This also includes the
spillway, powerplant, navigation lock, fish pass, etc., where these form part
of the length of the dam. If detached from the dam these structures should
not be included.

Liquefaction. A condition whereby soil undergoes continued deformation at a
constant low residual stress or with low residual resistance, due to the
buildup and maintenance of high pore water pressures, which reduces the
effective confining pressure to a very low value. Pore pressure buildup
leading to liquefaction may be due either to static or cyclic stress appli-
cations and the possibility of its occurrence will depend on the void ratio or
relative density of a cohesionless soil and the confining pressure.

Logboom. A chain of logs, drums, or pontoons secured end to end and floating
on the surface of a reservoir so as to divert floating debris, trash, and logs.

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