REEF, FRINGING - A reef attached to an insular or continental shore. 



REEF, SMID - SynonyTTious with BAR. 



REFERENCE PLANE - See DATUi'I PLANE. 



REFERENCE POINT - A specified location (in plan and/or elevation; to 

 which measurements are referred. 



PJuFERENCE STATION - A station for x^fhich tidal constants have previously 

 been determined and. which is used as a standard for the comparison 

 of simultaneous observations at a second station^ also a station 

 for vjhich independent daily predictions are given in the tide or 

 current tables from which corresponding predictions are obtained for 

 other stations by means of differences or factors. 



PlEFLECTED""WAVE - The wave that is returned seaward when a wave impinges 

 upon a very steep beach, barrier, or other reflecting surface. 



REFRACTION OF WATElil WAVES - (l) The process by which the direction of a 

 wave moving in shalloxv water at an angle to the contours is changed. 

 The part of the wave advancing in shallower water moves more slowly 

 than that part still advancing in deeper water^, causing the wave 

 crest to bend toward alinement with the unden-jater contours, 

 (2) The bending of wave crests by currents. (See Figure A-5) 



REFRACTION COEFFICIENT - The square root of the ratio of the spacing 



between adjacent orthogonals in deep water and in shallow water at 

 a selected point. When multiplied by the SHOALING FACTOR, this 

 becomes the VIAVE HEIGHT COEFFICIENT or the ratio of the refracted 

 wave height at any point to the deep vjater wave height. Also the 

 square root of the ENERGY COEFFICIENT. 



REFRACTION DIAGRAM - A drawing showing positions of wave crests and/or 

 orthogonals in a given area for a specific deep water wave period 

 and direction, (See Figure A-6) . 



RETARDATION - The amount of time by which corresponding tidal phases 

 grow later day by day (averages approximately 50 minutes). 



RETROGRESSION OF A BEACH - (l) A continuing landward movement of the 



shore line; (2) A net landward movement of the shore line over a 

 specified time. Also RECESSION. 



REVETrlENT - A facing of stone, concrete, etc., built to protect a scarp, 

 embankment or shore structure against erosion by wave action or 

 currents . 



RIA - A long narrox-j inlet, with depth gradually diminishing inward. 



A-25 



