Flood, levee, and erosion control glossary - U
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U/S
Abbreviation for "upstream of".
Unconfined Aquifer
An aquifer in which the water table is
at or near atmosphere pressure; the aquifer may or may not be saturated to the
top of the aquifer.
Underclearance
The lowest point of a bridge or other
structure over or across a river, stream, or watercourse that limits the
opening through which water flows. This is referred to as "low steel"
in some regions.
Underground Storage Tank (UST)
A tank system, including
its piping, that has at least 10% of its volume underground.
Uniform Depth
Depth is constant over channel length, and
channel slope, slope and boundary roughness are constant over the channel
depth.
Universal Soil Loss Equation (USLE)
(eFarm.ca) The Universal Soil Loss Equation (USLE) predicts the long term average annual rate of erosion on a field slope based on rainfall pattern, soil type, topography, crop system and management practices. USLE only predicts the amount of soil loss that results from sheet or rill erosion on a single slope and does not account for additional soil losses that might occur from gully, wind or tillage erosion. (www.eFarm.ca) Universal Soil Loss Equation (USLE): A = R x K x LS x C x P.
Unravel
To lose material from the edges of a revetment.
Unsteady Flow
State of flow where the depth of flow
changes with time.
Updrift
The direction opposite, or longshore, that of the
predominant movement of littoral materials.
Upper Bank
Portion of the streambank above the elevation
of the average water level of the stream.
Upstream
Along coasts with obliquely approaching waves there is a longshore (wave-driven) current. for this current one can define an upstream and a downstream direction. for example, on a beach with an orientation west-east with the sea to the north, the waves come from NW. then the current flows from west to east. Here, upstream is west of the observer, and east is downstream of the observer.
Urban Ecosystem
Areas that consist of a large number of
people living in close proximity to one another (e.g., cities and suburbs) and
serve as a center for residential and commercial activities.
Urban Flooding
Nuisance flooding of streets, underpasses, basements and other low-lying urban areas. Should not be confused with flash flooding. Usually due to poor drainage, or limited drainage capacity of urban systems. The amount and rate of precipitation that causes urban or Small Stream Flooding is usually constant for a specific community. In general, 0.5-1.0 inch (1.3-2.5 cm) of precipitation in one hour will cause at least minor urban/small stream flooding in most urbanized areas. Over one inch of rainfall in an hour will cause general urban flood problems, and may cause flash flooding.
Photo courtesy of US NRCS. |
Photo of Urban Flooding. |
Urban levee
A levee providing greater than a 10-year level of flood protection to a predominantly urban area.
Urban Runoff
Storm water from city streets and adjacent
domestic or commercial properties that carries pollutants of various kinds into
the sewer systems and receiving waters.
U.S. Army Corps of Engineers
The United States Army Corps
of Engineers (USACE) is made up of approximately 34,600 Civilian and 650
military members. Their military and civilian engineers, scientists and other
specialists work hand in hand as leaders in engineering and environmental matters.
Their workforce of biologists, engineers, geologists, hydrologists, natural
resource managers and other professionals meets the demands of changing times
and requirements as a vital part of America's Army.
U.S. Geological Survey
The USGS serves the Nation by
providing reliable scientific information to describe and understand the Earth;
minimize loss of life and property from natural disasters; manage water,
biological, energy, and mineral resources; and enhance and protect our quality
of life.
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For more information about Infrastructure Defense Technologies’ flood barriers and erosion control barriers and applications, please call us at 1-800-379-1822, email us at info@metalithH2O.com, info@infrastructure-defense.com or fill out our contact form.
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