EP 1110-2-13
28 Jun 96
A free-flow tunnel or open channel that conveys
different levels of the tube may be found relative to a
water to the upper end of a penstock; hence, the terms
point, usually the top or bottom of the tube, assumed
"headrace tunnel" and "headrace canal."
to be fixed. The system may be used to measure
settlement
during
embankment
construction
(Bartholomew, Murray, and Goins 1987).
A
Heel
The junction of the upstream face of a gravity or arch
reference benchmark is used to establish the top of
dam with the ground surface. For an embankment
the inclinometer casing. The instrument probe is
dam the junction is referred to as the upstream toe of
lowered to each slip joint in the casing, and the depth
the dam.
to each joint is read directly off the tape. Settlement
measurements are made as each section of casing is
added during embankment construction.
Height, above ground
The maximum height from natural ground surface to
the top of a dam.
Initial reservoir filling
A deliberate impoundment to meet project purposes
(a continuing process as successively higher pools are
Height, hydraulic
The vertical difference between the maximum design
attained for flood control projects).
water level and the lowest point in the original
streambed.
An arrangement of devices installed into or near dams
(i.e., piezometers, inclinometers, strain gages,
Height, structural
The vertical distance between the lowest point of the
measurement points, etc.) which provide for
excavated foundation to the top of the dam.
measurements that can be used to evaluate the
structural behavior and performance parameters of
the structure.
Hydrograph, breach or dam failure
A flood hydrograph resulting from a dam breach.
Intake
Any structure in a reservoir, dam, or river through
Hydrograph, flood
A graphical representation of the flood discharge with
which water can be discharged.
respect to time for a particular point on a stream or
river.
Inundation map
A map delineating the area that would be flooded by a
particular flood event.
Hydrograph, unit
A hydrograph with a volume of 1 inch of runoff
resulting from a storm of a specified duration and
Length of dam
areal distribution. Hydrographs from other storms of
The length along the top of the dam. This also
the same duration and distribution are assumed to
includes the spillway, powerplant, navigation lock,
have the same time base but with ordinates of flow in
fish pass, etc., where these form part of the length of
proportion to the runoff volumes.
the dam. If detached from the dam these structures
should not be included.
Hypocenter
The point or focus within the earth which is the center
of an earthquake and the origin of its elastic waves.
Liquefaction
A condition whereby soil undergoes continued
deformation at a constant low residual stress or with
Inclinometer
An instrument, usually consisting of a metal or plastic
low residual resistance, due to the buildup and
tube inserted in a drill hole and a sensitized monitor
maintenance of high pore water pressures, which
either lowered into the tube or fixed within the tube.
reduces the effective confining pressure to a very low
This measures at different points the tube's inclination
value. Pore pressure buildup leading to liquefaction
to the vertical. By integration, the lateral position at
may be due either to static or cyclic stress applications
B-9
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