EM 1110-2-1100 (Change 1)
31 Jul 03
H
HALCOCLINE
A zone in which salinity changes rapidly.
HALF-TIDE LEVEL
A plane midway between MEAN HIGH WATER and MEAN LOW WATER, also called MEAN TIDE LEVEL.
HARBOR (British, HARBOUR)
Any protected water area affording a place of safety for vessels. See also PORT. A harbor may be natural or
man-made.
HARBOR OSCILLATION (HARBOR SURGING)
The nontidal vertical water movement in a harbor or bay. Usually the vertical motions are low; but when oscilla-
tions are excited by a tsunami or storm surge, they may be quite large. Variable winds, air oscillations, or surf beat also may
cause oscillations. See SEICHE.
HARD DEFENSES
General term applied to impermeable coastal defense structures of concrete, timber, steel, masonry, etc, which
reflect a high proportion of incident wave energy.
HEAD OF RIP
The part of a rip current that has widened out seaward of the breakers. See also CURRENT, RIP; CURRENT,
FEEDER; and NECK (RIP).
HEADLAND (HEAD)
(1) A comparatively high promontory with either a CLIFF or steep face extending out into a body of water, such as
a sea or lake. An unnamed HEAD is usually called a headland. (2) The section of RIP CURRENT which has widened out
seaward of the BREAKERS, also called HEAD OF RIP. (3) Seaward end of BREAKWATER or dam.
HEADWATER LEVEL
The level of water in the reservoir.
HEAVE
(1) The vertical rise or fall of the waves or the sea. (2) The translational movement of a craft parallel to its vertical
axis. (3) The net transport of a floating body resulting from wave action.
HIGH SEAS
This term, in municipal and international law, denotes the continuous body of salt water in the world that is
navigable in its character and that lies outside territorial waters and maritime belts of the various countries.
HIGH TIDE, HIGH WATER (HW)
The maximum elevation reached by each rising tide. See TIDE. (See Figure II-5-16.)
HIGH WATER (HW)
Maximum height reached by a rising tide. The height may be solely due to the periodic tidal forces or it may have
superimposed upon it the effects of prevailing meteorological conditions. Nontechnically, also called the HIGH TIDE.
HIGH WATER LINE
In strictness, the intersection of the plane of mean high water with the shore. The shoreline delineated on the
nautical charts of the National Ocean Service is an approximation of the high water line. For specific occurrences, the highest
elevation on the shore reached during a storm or rising tide, including meteorological effects.
A-36
Appendix A Glossary of Coastal Terminology
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