Current, Longshore - Current in the breaker zone moving essentially parallel to shore and usually caused by
waves breaking at an angle to shore. Also called alongshore current.
Deep Water - Area where surf ace waves are not influenced by the bottom. Generally, a point where the depth is
greater than one-half the surface wavelength.
Diffraction- Progressive reduction in wave height when a wave spreads into the shadow zone behind a barrier
after the wave has passed its end.
Diurnal - Period or cycle lasting approximately one day. A diurnal tide has one high and one low in each cycle.
Downdrift - Direction of alongshore movement of littoral materials.
Dune - Hill, bank, bluff, ridge, or mound of loose, wind-blown material, usually sand.
Duration - Length of time the wind blows in nearly the same direction across a FETCH (generating area).
Ebb Tide - Part of the tidal cycle between high water and the next low. The falling tide.
Equilibrium - State of balance or equality of opposing forces.
Erosion - Wearing away of land by action of natural forces.
Fetch - Area where waves are generated by wind, which has steady direction and speed. Sometimes called
FETCH LENGTH.
Fetch Length - Horizontal direction (in the wind direction) over which a wind generates waves. In sheltered
waters, often the maximum distance that wind can blow across water.
Filter Cloth - Synthetic textile with openings for water to escape,
but which prevents passage of soil particles.
Flood Tide - Part of the tidal cycle between low water and the next high. The rising tide.
Glacial Till - Unstratified glacial drift consisting of unsorted clay, sand, gravel, and boulders, intermingled.
Longshore - Parallel to and near the shoreline: same as ALONGSHORE.
Longshore Transport Rate - Rate of transport of littoral material parallel to shore.
Usually expressed in cubic
yards per year.
Low Tide - Minimum elevation reached by each falling tide.
Low Water Datum (LWD) - The elevation of each of the Great Lakes to which are referenced the depths shown
on navigation charts and the authorized depths of navigation projects.
Marsh - Area of soft, wet, or periodically inundated land, generally treeless, and usually characterized by grasses
and other low growth.
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