Glossary
325
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 predominant alongshore movement of littoral materials.
Dune : A hill, bank, bluff, ridge or mound of loose, wind-blown material, usually
sand.
Duration : The 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 : The wearing away of land by the action of natural forces.
Fetch : Area where waves are generated by wind which has a relatively steady
direction and speed. Sometimes called FETCH LENGTH. Also, unobstructed
distance over water where such generation takes place.
Fetch Length : Horizontal direction (in the wind direction) over which a wind
generates waves. In sheltered waters, often the maximmn 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.
Foreshore : The part of the shore lying between the crest of the seaward berm (or
upper limit of wave wash) and the water's edge at low water. The foreshore
is ordinarily traversed by the runup and return of the waves.
Functional life : The period of time during which a structure performs as
intended. Performance can be expressed in terms of benefits obtained versus
the cost of installation and maintenance.
325
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 predominant alongshore movement of littoral materials.
Dune : A hill, bank, bluff, ridge or mound of loose, wind-blown material, usually
sand.
Duration : The 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 : The wearing away of land by the action of natural forces.
Fetch : Area where waves are generated by wind which has a relatively steady
direction and speed. Sometimes called FETCH LENGTH. Also, unobstructed
distance over water where such generation takes place.
Fetch Length : Horizontal direction (in the wind direction) over which a wind
generates waves. In sheltered waters, often the maximmn 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.
Foreshore : The part of the shore lying between the crest of the seaward berm (or
upper limit of wave wash) and the water's edge at low water. The foreshore
is ordinarily traversed by the runup and return of the waves.
Functional life : The period of time during which a structure performs as
intended. Performance can be expressed in terms of benefits obtained versus
the cost of installation and maintenance.