BACKBEACH - See BACKSHORE . 



BACKRUSH - The seaward return of the water following the uprush of the 

 waves . For any given tide stage the point of farthest return sea- 

 ward of the backrush is known as the LIMIT of BACKRUSH or LIMIT 

 BACKWASH. (See Figure A- 2.) 



BACKSHORE - That zone of the shore or beach lying between the foreshore 

 and the coastline and acted upon by waves only during severe storms, 

 especially when combined with exceptionally high water. Also 

 BACKBEACH. It comprises the BERM or BERMS. (See Figure A-1.) 



BACKWASH - (1) See BACKRUSH. (2) Water or waves thrown back by an 

 obstruction such as a ship, breakwater, or cliff. 



BANK - (1) The rising ground bordering a lake, river, or sea; of a 



river or channel, designated as right or left as it would appear 

 facing downstream. (2) An elevation of the sea floor of large 

 area, located on a Continental (or island) Shelf and over which 

 the depth is relatively shallow but sufficient for safe surface 

 navigation; a group of shoals. (3) In its secondary sense, a 

 shallow area consisting of shifting forms of silt, sand, mud, and 

 gravel, but in this case it is only used with a qualifying word 

 such as "sandbank" or "gravelbank". 



BAR - A submerged or emerged embankment of saad, gravel, or other un- 

 consolidated material built on the sea floor in shallow water by 

 waves and currents . See BAYMOUTH BAR, CUSPATE BAR. (See Figures 

 A- 2 and A-9.) 



BARRIER BEACH - A bar essentially parallel to the shore, the crest of 

 which is above normal high water level. Also called OFFSHORE 

 BARRIER and BARRIER ISLAND. (See Figure A-9.) 



BARRIER LAGOON - A bay roughly parallel to the coast and separated from 



the open ocean by barrier islands. Also the body of water encircled 

 by coral islands and reefs, in which case it may be called an atoll 

 lagoon. 



BARRIER REEF - A coral reef parallel to and separated from the coast by 

 a lagoon that is too deep for coral growth. Generally, barrier 

 reefs follow the coasts for long distances, and are cut through at 

 irregular intervals by channels or passes. 



BASIN, BOAT - A naturally or artificially enclosed or nearly enclosed 

 harbor area for small craft. 



BATHYMETRY - The measurement of depths of water in oceans, seas, and 

 lakes; also information derived from sudi measurements. 



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