groin:
A structure built from the bank of a stream in a direction
transverse to the current to redirect the flow or reduce flow
velocity. Many names are given to this structure, the most
common being "spur," "spur dike," "transverse dike," "jetty,"
etc. Groins may be permeable, semi-permeable, or
impermeable.
grout:
A fluid mixture of cement and water or of cement, sand, and
water used to fill joints and voids.
guide bank:
A dike extending upstream from the approach embankment at
either or both sides of the bridge opening to direct the flow
through the opening. Some guidebanks extend downstream
from the bridge (also spur dike).
hardpoint:
A streambank protection structure whereby "soft" or erodible
materials are removed from a bank and replaced by stone or
compacted clay. Some hard points protrude a short distance
into the channel to direct erosive currents away from the bank.
Hard points also occur naturally along streambanks as passing
currents remove erodible materials leaving nonerodible
materials exposed.
headcutting:
Channel degradation associated with abrupt changes in the
bed elevation (headcut) that generally migrates in an upstream
direction.
helical flow:
Three-dimensional movement of water particles along a spiral
path in the general direction of flow. These secondary-type
currents are of most significance as flow passes through a
bend; their net effect is to remove soil particles from the cut
bank and deposit this material on a point bar.
The applied science concerned with the behavior and flow of
liquids, especially in pipes, channels, structures, and the
ground.
hydraulic model:
A small-scale physical or mathematical representation of a flow
situation.
hydraulic problem:
An effect of streamflow, tidal flow, or wave action such that the
integrity of the highway facility is destroyed, damaged, or
endangered.
hydraulic radius:
The cross-sectional area of a stream divided by its wetted
perimeter.
hydraulic structures:
The facilities used to impound, accommodate, convey or
control the flow of water, such as dams, weirs, intakes,
culverts, channels, and bridges.
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