clear-water scour:
Scour at a pier or abutment (or contraction scour) when there
is no movement of the bed material upstream of the bridge
crossing at the flow causing bridge scour.
cobble:
A fragment of rock whose diameter is in the range of 64 to 250
mm.
concrete revetment:
Unreinforced or reinforced concrete slabs placed on the
channel bed or banks to protect it from erosion.
confluence:
The junction of two or more streams.
constriction:
A natural or artificial control section, such as a bridge crossing,
channel reach or dam, with limited flow capacity in which the
upstream water surface elevation is related to discharge.
contact load:
Sediment particles that roll or slide along in almost continuous
contact with the streambed (bed load).
contraction:
The effect of channel or bridge constriction on flow
streamlines.
contraction scour:
Contraction scour, in a natural channel or at a bridge crossing,
involves the removal of material from the bed and banks
across all or most of the channel width. This component of
scour results from a contraction of the flow area at the bridge
which causes an increase in velocity and shear stress on the
bed at the bridge. The contraction can be caused by the
bridge or from a natural narrowing of the stream channel.
Coriolis force:
The inertial force caused by the Earth's rotation that deflects a
moving body to the right in the Northern Hemisphere.
countermeasure:
A measure intended to prevent, delay or reduce the severity of
hydraulic problems.
crib:
A frame structure filled with earth or stone ballast, designed to
reduce energy and to deflect streamflow away from a bank or
embankment.
critical shear stress:
The minimum amount of shear stress required to initiate soil
particle motion.
crossing:
The relatively short and shallow reach of a stream between
bends; also crossover or riffle.
cross section:
A section normal to the trend of a channel or flow.
current:
Water flowing through a channel.
current meter:
An instrument used to measure flow velocity.
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