EM 1110-2-1100 (Change 1)
31 Jul 03
GLOBAL POSITIONING SYSTEM (GPS)
A navigational and positioning system developed by the U.S. Department of Defense, by which the location of a
position on or above the Earth can be determined by a special receiver at that point interpreting signals received
simultaneously from several of a constellation of special satellites.
GORGE
(1) The deepest portion of an inlet, the THROAT. (2) A narrow, deep valley with nearly vertical rock walls.
GRADED BEDDING
An arrangement of particle sizes within a single bed, with coarse grains at the bottom of the bed and progressively
finer grains toward the top of the bed.
GRADIENT
(1) A measure of slope (soil- or water-surface) in meters of rise or fall per meter of horizontal distance. (2) More
general, a change of a value per unit of distance, e.g. the gradient in longshore transport causes erosion or accretion. (3) With
reference to winds or currents, the rate of increase or decrease in speed, usually in the vertical; or the curve that represents
this rate.
GRADING
Distribution, with regard to size or weight, of individual stones within a bulk volume; heavy, light and fine grading
are distinguished.
GRADUAL CLOSURE METHOD
Method in which the final closure gap in a dam is closed gradually either by the vertical or horizontal closure
method; this in contradiction with a sudden closure.
GRANULAR FILTER
Band of granular material which is incorporated in an embankment, dam, dike, or bottom protection and is graded
so as to allow seepage to flow across or down the filter zone without causing the migration of the material adjacent to the
filter.
GRAVEL
Unconsolidated natural accumulation of rounded rock fragments coarser than sand but finer than pebbles (2-4 mm
diameter).
GRAVITY WAVE
A wave whose velocity of propagation is controlled primarily by gravity. Water waves more than 5 cm long are
considered gravity waves. Waves longer than 2.5 cm and shorter than 5 cm are in an indeterminate zone between
CAPILLARY and GRAVITY WAVES. See RIPPLE.
GROIN (British, GROYNE)
Narrow, roughly shore-normal structure built to reduce longshore currents, and/or to trap and retain littoral material.
Most groins are of timber or rock and extend from a SEAWALL, or the backshore, well onto the foreshore and rarely even
further offshore. See T-GROIN, PERMEABLE GROIN, IMPERMEABLE GROIN.
GROIN BAY
The beach compartment between two groins.
GROIN SYSTEM
A series of groins acting together to protect a section of beach. Commonly called a GROIN field.
GULF
A relatively large portion of the ocean or sea extending far into land; the largest of various forms of inlets of the sea
(e.g., Gulf of Mexico, Gulf of Aqaba).
A-34
Appendix A Glossary of Coastal Terminology
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