It had been established that if the configuration of a given stretch of beach remains 

 basically the same over a period of years (allowing for seasonal variation), then it is generally 

 considered to be in equilibrium. Because a beach is always changing, equilibrium means that 

 the amount of sand moving into the stretch of beach is the same as the amount of sand 

 being carried away by wave or current action (viewing the stretch of beach in this instance 

 as an open system). 



If, for some reason, the sand supply moving into the same system is decreased, then 

 erosion of the existing shoreline will occur. This is because the material available for the 

 waves to transport is now of a lesser amount, while the energy of the waves has remained 

 the same. Consequently, this energy is utilized in eroding the beach. 



Based on these fundamental principles of nature, two innovative shore protection 

 techniques became increasingly common in the years following World War II. The first of 

 these is known as sand bypassing. Tliis technique has most often been used where jetties 

 and/or breakwaters have been built. These structures, by either extending into the nearshore 

 zone or altering wave conditions, can interrupt the natural movement of sand which occurs 

 along tlie coastline generally in one predominant direction, by means of the longshore 

 current. Sand bypassing is a technique by which sand is transferred, using one of several 

 mechanical methods, from the accreting side of tlie structure to the eroding side. In this 

 way, the sand is again made available for transport by the waves along tlie downdrift shore, 

 and the beach along this downdrift shore can thereby be regained and stabilized. 



One of the first places in the United States (and perhaps in the world) where this concept 

 was actually applied was at Santa Barbara, California, in 1935 where an erosion problem had 

 arisen after local interests had constructed a breakwater a few years previously. This first 

 effort of sand bypassing at Santa Barbara was not completely successful in that the 

 transferred sand was placed in about 22 feet of water— too deep to be picked up by the 

 longshore current.^ ^^ Later work, including studies and field inspection by the BEB, 

 corrected the situation by having the sand placed directly on the downdrift beach. With 

 periodic repetition of this bypassing operation, the seriousness of the erosion problem east 

 of the Santa Barbara breakwater gradually eased. Some 8 miles of eroding beach along the 

 downdrift shoreUne were stabilized. 



After World War II, continued improvement in equipment facilitated greater use of sand 

 bypassing. This was combined with increasing knowledge of shoreline processes and more 

 factual data concerning the amount of sandy material that annually moved along a given 

 unit of beach. A considerable part of the research effort of the BEB staff was directed 

 toward this important topic, and helped provide some valuable answers. 



The second shore protection technique which became more common starting around the 

 late 1940's, is what is known as beach nourishment or beach replenishment. This involves 

 the periodic placement by mechanical means of a given amount of sand (which is obtained 

 from outside the coastal unit in question) onto a beach to either: (a) Provide protection by 



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