EM 1110-2-1100 (Change 1)
31 Jul 03
FIRTH
A narrow arm of the sea; also, the opening of a river into the sea.
FLOOD
(1) Period when tide level is rising; often taken to mean the flood current which occurs during this period (2) A
flow beyond the carrying capacity of a channel.
FLOOD CHANNEL
Channel located on ebb-tidal shoal that carries the flood tide over the tidal flat into the back bay or lagoon.
FLOOD CURRENT
The movement of a tidal current toward the shore or up a tidal stream. In the semidiurnal type of reversing current,
the terms greater flood and lesser flood are applied respectively to the flood currents of greater and lesser velocity each day.
The terms maximum flood and minimum flood are applied to the maximum and minimum velocities of a flood current the
velocity of which alternately increases and decreases without coming to slack or reversing. The expression maximum flood is
also applicable to any flood current at the time of greatest velocity.
FLOOD GATE
A gravity outlet fitted with vertically-hinged doors, opening if the inner water level is higher than the outer water
level, so that drainage takes place during low water.
FLOOD INTERVAL
The interval between the transit of the moon over the meridian of a place and the time of the following flood.
FLOOD MARK
Proof of any kind on the shoreline, or on structures like bridge abutments, used to determine the highest level
attained by the water surface during the flood (note: the height of the flood mark usually includes the wave run-up).
FLOOD PLAIN
1) A flat tract of land bordering a river, mainly in its lower reaches, and consisting of ALLUVIUM deposited by the
river. It is formed by the sweeping of the meander belts downstream, thus widening the valley, the sides of which may
become some kilometers apart. In time of flood, when the river overflows its banks, sediment is deposited along the valley
banks and plains. (2) Synonymous with 100-year floodplain. The land area susceptible to being inundated by stream derived
waters with a 1 percent chance of being equaled or exceeded in any given year.
FLOOD RAMP
Seaward-dipping sand platform dominated by flood-tidal currents, located on ebb-tidal shoal near the opening to the
inlet.
FLOOD ROUTING
The determination of the attenuating effect of storage on a river-flood passing through a valley by reason of a
feature acting as control (e.g. a reservoir with a spillway capacity less than the flood inflow, or the widening or narrowing of a
valley).
FLOOD TIDAL DELTA
The bulge of sand formed at the landward mouth of TIDAL INLETS as a result of flow expansion.
FLOOD TIDE
The period of tide between low water and the succeeding high water; a rising tide. (See Figure II-5-16.)
FLOOD WALL, SPLASH WALL
Wall, retired from the seaward edge of the seawall crest, to prevent water from flowing onto the land behind.
FLORA
The entire group of plants found in an area.
Appendix A Glossary of Coastal Terminology
A-31
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