EM 1110-2-1100 (Change 1)
31 Jul 03
ORTHOGONAL
On a wave-refraction diagram, a line drawn perpendicularly to the wave crests. Also called WAVE RAY. (See
Figure II-3-4)
OSCILLATION
(1) A periodic motion backward and forward. (2) Vibration or variance above and below a mean value.
OSCILLATORY WAVE
A wave in which each individual particle oscillates about a point with little or no permanent change in mean
position. The term is commonly applied to progressive oscillatory waves in which only the form advances, the individual
particles moving in closed or nearly closed orbits. Compare WAVE OF TRANSLATION. See also ORBIT.
OUTCROP
A surface exposure of bare rock, not covered by soil or vegetation.
OUTFALL
A structure extending into a body of water for the purpose of discharging sewage, storm runoff, or cooling water.
OUTFLANKING
EROSION behind or around the land-based end of a GROIN, JETTY, or BREAKWATER or the terminus of a
BULKHEAD, REVETMENT, or SEAWALL, usually causing failure of the structure or its function
OVERSPLASH
The water that splashes over the top of a BREAKWATER, SEAWALL, etc.
OVERTOPPING
Passing of water over the top of a structure as a result of wave runup or surge action.
OVERWASH
(1) The part of the UPRUSH that runs over the crest of a BERM or structure and does not flow directly back to the
ocean or lake. (2) The effect of waves overtopping a COASTAL DEFENSE, often carrying sediment landwards which is
then lost to the beach system.
Appendix A Glossary of Coastal Terminology
A-55
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