ETL 1110-2-367
31 Mar 95
Interception systems
gravity must be at a higher elevation than the river stage against
Sewers or ditches provided to connect existing sewers or
which it functions. Some pressure conduits may serve as
channels which discharge through the line-of-protection by
discharge conduits from pumping stations.
means of gravity outlets, pumping stations, or pressure
Pump efficiency
conduits.
The percentage of rated pump capacity actually obtained during
Interior stage
pump operations (100 percent at average river stages, less than
Water level on the protected side of the line-of-protection.
100 percent at higher river stages).
Interior system
Pumping station
Structural and nonstructural flood loss reduction measures
Pumps located at or near the line-of-protection to discharge
located behind the line-of-protection. These measures may
interior flows over or through the levees or flood walls (or
consist of (a) water management measures of gravity outlets,
through pressure lines) when free outflow through gravity
pumping stations, interior detention storage, diversions,
outlets is prevented by exterior stages.
pressure conduits, and hillside reservoirs; (2) facility protection
Residual damage
measures of flood proofing and structure relocation; and (c)
development management measures of floodplain regulations
Flood damage remaining after implementation of the flood loss
and flood emergency warning-preparedness plans.
reduction measures.
Line-of-protection
Seepage
Location of levee or wall that prevents flood waters from
Water that passes through or beneath the line-of-protection
entering an area.
when the exterior water surface elevation is higher than the
interior water surface elevation.
Lower interior subbasin
Standard project storm
An interior subbasin that directly contributes to flow behind the
line-of-protection, normally considered the floodplain portion of
Hypothetical storm distribution applicable to basin areas 26 to
the contributing area.
2,590 sq km (10 to 1,000 sq miles) located east of 105 deg
longitude. Determined according to the criteria discussed in EM
National economic development (NED) plan
1110-2-1411.
The plan that maximizes net national economic development
Structural measures
benefits.
Measures designed to reduce flood losses by construction of
Nonstructural measures
levees, gravity outlets, pumping stations, detention storage,
Measures designed to reduce flood losses by implementation of
reservoirs, and diversions.
facility flood proofing, raising, or relocation; and development
Tailwater
regulations and flood warning-emergency preparedness
planning actions.
The depth of water at a culvert on the downstream side, as
measured from the downstream invert of the culvert.
Outlet control
Tieback levee (Flank levee)
A condition where culvert capacity is limited by downstream
conditions or by the flow capacity of the barrel, typically
Levee that extends from the river, lake, or coast to a bluff line.
resulting in subcritical flow.
Part of the line-of-protection.
Overflows
Total pumping head
Situation in which the water surface elevation in the interior
This value represents the operating head of a pumping unit at
ponding area rises to a level that causes flows to naturally spill
various flow capacities. The total pumping head is the sum of
from one interior area into an adjacent interior area.
the estimated head loss and the static head.
Pressure conduits
Transfer relation
Closed conduits designed to convey interior flows through the
Adjustment of the main river stage hydrograph from the index
line-of-protection under internal pressure. The inlet to a
location to a primary or secondary gravity outlet location.
pressure conduit that discharges interior flows by force of
B-2
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