EP 1110-2-13
28 Jun 96
x.
Tailings dam. See mine tailings dam.
See saddle dam.
Dam failure
Diversion channel, canal, or tunnel
The uncontrolled release of impounded water. It is
A waterway used to divert water from its natural
recognized that there are lesser degrees of failure and
course. The term is generally applied to a temporary
that any malfunction or abnormality outside the
arrangement, e.g., to by-pass water around a damsite
design assumptions and parameters which adversely
during construction. "Channel" is normally used
affect a dam's primary function of impounding water
instead of "canal" when the waterway is short.
is properly considered a failure. They are, however,
normally amenable to corrective action.
Drain, blanket
A layer of pervious material placed to facilitate
drainage of the foundation and/or embankment.
Dam safety
This term not only covers the safeguarding of human
life and downstream property but also the satisfactory
Drain, chimney
operation of the structure. The safety of a dam
A vertical or inclined layer of pervious material in an
manifests itself in being free of conditions that could
embankment to facilitate and control drainage of the
lead to the deterioration or destruction of the dam.
embankment fill.
The margin which separates the actual conditions of a
dam from those leading to its damage or destruction
Drain, toe
is a measure of its safety. To be safe, a dam has to
A system of pipe and/or pervious material along the
have appropriate reserves, taking into account all
downstream toe of a dam used to collect seepage
scenarios of normal utilization and exceptional hazard
from the foundation and embankment and convey it
which it may have to withstand during its life
to a free outlet.
(International Commission on Large Dams 1987).
Drainage area
The area which drains to a particular point on a river
Dam safety preparedness
The quality or state of being prepared to deal with
or stream.
emergency conditions which endanger the structural
integrity of the dam and/or downstream property and
Drainage curtain
human life.
Also called drainage wells or relief wells. A line of
vertical wells or boreholes to facilitate drainage of the
foundation and abutments and to reduce water
Design water level
The maximum water elevation including the flood
pressure.
surcharge that a dam is designed to withstand.
Drawdown
The difference between a water level and a lower
Design wind
The most severe wind that is reasonably possible at a
water level in a reservoir within a particular time.
particular reservoir for generating wind setup and
Used as a verb, it is the lowering of the water surface.
runup. The determination will generally include the
results of meteorologic studies which combine wind
Earthquake
velocity, duration, direction, and seasonal distribution
A sudden motion or trembling in the earth caused by
characteristics in a realistic manner.
the abrupt release of accumulated stress along a fault.
Diaphragm wall (membrane)
Earthquake, Maximum Credible (MCE)
A sheet, thin zone, or facing made of an impervious
The most severe earthquake that can be expected to
material such as concrete, steel, wood, or plastic.
occur at a given site on the basis of geologic and
Also see core wall.
seismological evidence.
Dike
Earthquake, Maximum Design (MDE)
B-5
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