EM 1110-2-1100 (Change 1)
31 Jul 03
DOWNWELLING
A downward movement (sinking) of surface water caused by onshore Ekman transport, converging CURRENTS, or
when a water mass becomes more dense than the surrounding water.
DRAINAGE BASIN
Total area drained by a stream and its tributaries.
DREDGED CHANNEL
An artificially maintained sea lane extending from an inland water body into the marginal sea to accomodate vessel
traffic through coastal shallows.
DREDGED MATERIAL PLACEMENT SITE
Designated area for dredged material placement. In the United States, designated areas must be coordinated with
the Environmental Protection Agency and resource agencies such as the U. S. Fish and Wildlife Service and the National
marine Fisheries Service for environmental compliance and with local interests for capacity and acceptability.
DREDGING
The practice of excavating or displacing the bottom or shoreline of a water body. Dredging can be accomplished
with mechanical or hydraulic machines. Most is done to maintain channel depths or berths for navigational purposes; other
dredging is for shellfish harvesting, for cleanup of polluted sediments, and for placement of sand on beaches.
DRIFT (noun)
(1) Sometimes used as a short form for LITTORAL DRIFT. (2) The speed at which a current runs. (3) Floating
material deposited on a beach (driftwood). (4) A deposit of a continental ice sheet; e.g., a DRUMLIN.
DRIFT CURRENT
A broad, shallow, slow-moving ocean or lake current.
DRIFT SECTOR
A particular reach of marine shore in which LITTORAL DRIFT may occur without significant interruption, and
which contain any and all natural sources of such drift, and also any accretion shore forms accreted by such drift.
DROMOND
A large medieval fast-sailing galley or cutter.
DROWNED COAST
A shore with long, narrow channels, implying that subsidence of the coast has transformed the lower portions of
river valleys into tidal estuaries.
DRUMLIN
A low, smoothly-rounded, elongate hill of compact glacial till built under the margin of the ice and shaped by its
flow.
DRYING BEACH
That part of the beach which is uncovered by water (e.g. at low tide). Sometimes referred to as 'SUBAERIAL'
beach.
DUNES
(1) Ridges or mounds of loose, wind-blown material, usually sand. (See Figure IV-2-11.) (2) Bed forms smaller
than bars but larger than ripples that are out of phase with any water-surface gravity waves associated with them.
DURABILITY
The ability of a rock to retain its physical and mechanical properties (i.e. resist degradation) in engineering service.
Appendix A Glossary of Coastal Terminology
A-25
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