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Potential Drift Accumulation at Bridges

GLOSSARY

accretion:
growth by gradual external addition of elements
boom:
a series of connected floating units designed to deflect or contain floating material
cofferdam:
a watertight enclosure pumped dry to allow construction below water level
debris flow:
non-Newtonian flow of a dense, plastic mixture of soil, rock, water, and trees
debris torrent:
debris flow occuring in a steep stream channel
FHWA:
Federal Highway Administration
flood plain:
the area of a valley bottom outside the stream channel and covered by water during floods
freeboard:
the distance between the water level and the lowest part of a bridge superstructure
hydrostatic forces:
forces generated by the weight of standing water
landslide:
gravity-driven movement of a mass of soil or rock
lingulate bar:
mid-channel sediment bar with a gently rising upstream face and a steep downstream face
low steel:
the lowest horizontal part of the bridge superstructure. When the water level is at or above low steel, the superstructure is partly immersed.
point bar:
a sediment bar that forms along the base of the convex bank of a channel bend
scroll bar:
a longitudinal sediment bar in the channel parallel to the convex bank of a channel bend
thalweg:
the line of greatest depth along a stream channel
thread:
the line of fastest flow at the water surface. The thread often, but not always, lies over the thalweg.
trash rack:
a grating or series of pilings for retaining floating objects
USGS:
United States Geological Survey
wind throw:
the uprooting of a tree by wind
WSPRO:
a one-dimensional, steady-flow step-backwater model containing specialized routines for bridge contractions, multiple openings, and supercritical-flow reaches.

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