EM 1110-2-1100 (Change 1)
31 Jul 03
G
GABION
(1) Steel wire-mesh basket to hold stones or crushed rock to protect a bank or bottom from erosion. (2) Structures
composed of masses of rocks, rubble or masonry held tightly together usually by wire mesh so as to form blocks or walls.
Sometimes used on heavy erosion areas to retard wave action or as a foundation for BREAKWATERS or JETTIES.
GALE
A wind between a strong breeze and a storm. A continuous wind blowing in degrees of moderate, fresh, strong, or
whole gale and varying in velocity from 28 to 47 nautical miles per hour (see BEAUFORT SCALE).
GAUGE (GAGE)
Instrument for measuring the water level relative to a datum or for measuring other parameters.
GENERATING AREA
In wave forecasting, the continuous area of water surface over which the wind blows in nearly a constant direction.
Sometimes used synonymously with FETCH LENGTH. Also FETCH.
GEOGRAPHICAL INFORMATION SYSTEM (GIS)
Database of information which is geographically referenced, usually with an associated visualization system.
GEOGRAPHIC MILE
Unit of linear measure equal to one minute of latitude at the equator. See NAUTICAL MILE.
GEOMETRIC MEAN DIAMETER
The diameter equivalent of the arithmetic mean of the logarithmic frequency distribution. In the analysis of beach
sands, it is taken as that grain diameter determined graphically by the intersection of a straight line through selected boundary
sizes, (generally points on the distribution curve where 16 and 84 percent of the sample is coarser by weight) and a vertical
line through the median diameter of the sample.
GEOMETRIC SHADOW
In wave diffraction theory, the area outlined by drawing straight lines paralleling the direction of wave approach
through the extremities of a protective structure. It differs from the actual protected area to the extent that the diffraction and
refraction effects modify the wave pattern.
GEOMORPHOLOGY
(1) That branch of physical geography which deals with the form of the Earth, the general configuration of its
surface, the distribution of the land, water, etc. (2) The investigation of the history of geologic changes through the
interpretation of topographic forms.
GEOPHYSICS
The study of the physical characteristics and properties of the earth, usually employing quantitative physical
methods.
GEOTEXTILE
A synthetic fabric which may be woven or non-woven used as a filter.
GLACIER
A large body of ice moving slowly down a slope of valley or spreading outward on a land surface (e.g., Greenland,
Antarctica) and surviving from year to year.
GLACIO-ISOSTACY
The state of hydrostatic equilibrium of the earth's crust as influenced by the weight of glacier ice.
Appendix A Glossary of Coastal Terminology
A-33
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