built up by the action of the sea over a long period. When this profile 

 has reached the stage of stability - that is, when the progradation, or 

 the building up of the beach, compensates for any retrogradation, or 

 eroding away - it is usually termed the "profile of equilibrium", and 

 thus it is the ultimate object in any beach reclamation - to restore the 

 profile of equilibrium. It will be appreciated, therefore, that the 

 restoration of such a profile rests largely on the restoration of the 

 lower beach to its correct position and until such a stage is reached, 

 any replenishment of the upper reaches would be of little avail. 



UNDERWATER MOVEMENT OP SAND 



Much importance, therefore, has been given to the carrying out of 

 regular underwater surveys, either by soundings taken by mechanical 

 devices or by investigations by divers. In this regard, it is important 

 to determine at which depth the maximum movement of sand takes place. 

 In view of the doubts that exist as to whether there is much movement in 

 deep water positions, it is useful to refer to the comprehensive experi- 

 ments which were carried out by the Beach Erosion Board of the United 

 States to test the effect of offshore dumping in the reclamation of 

 beaches. It was proved conclusively that to be of any material assist- 

 ance in shore reclamation, dumping of sand must take place within the 

 "breaker" zone, that is, within the sphere of influence of the waves of 

 translation. For example, at the Long Branch, New Jersey experiments 

 (1948 - 1949) sand was deposited in 38 feet of water with negative re- 

 sults. At Atlantic City (1935 - 1942) dumping in 15 to 25 feet depth of 

 water was equally ineffective, while at Santa Barbara, California, (1935- 

 1946) where the conditions generally were very similar to those appertain- 

 ing to Durban, the experiments failed to establish any accretion of sand 

 when dumped within 20 feet depth of water. 



Verification of these facts is borne out by the off-shore dumping of 

 the harbour dredgers at Durban itself. For years the sand taken from the 

 harbour entrance has been dumped at a point about a mile due east of the 

 end of the Innes Breakwater. Today there is a mound on the seabed at a 

 peak depth of eight fathoms and about 40 feet high, representing over 

 10,000,000 cubic yards of sand. It is obvious that there has been very 

 little movement from this site. 



LITTORAL DRIFT 



The importance of the "near shore" area in its influence upon beach 

 erosion is therefore obvious, and there is no doubt that the movement of 

 the beach material takes place largely within this zone, motivated by the 

 in-shore currents and the littoral drift, and the effect of these agents 

 has been carefully studied in relation to the Durban problem. The 

 generally accepted theory in regard to this aspect is that the littoral 

 drift, running in a north-easterly direction, is partly induced as an 



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