THE WIND ELEMENT IN BEACH EROSION 



By 



Martin A , Mason 

 Chief J Engineering and Research Branch 

 Beach Erosion Board 

 (Presented at Symposium on Hydroraeteorological Problems, American 

 Geophysical Union, 2 May 1950) 



The art of beach protection against loss of sand has been develop- 

 ing for decases through the thought and experiment of engineers, geo- 

 logists 5 and others whose interest derived chiefly from circumstance and 

 only rarely for other reasons. Early students of shore control problems 

 had little to guide their thinking and experiment other than their ob- 

 servational acumen 6 Thus, waves were recognized as a factor causing 

 transport and possible loss of sand, but local wind, usually most evident 

 when waves ware observed, was considered to be of prime importance o 

 Possibly much of the regard in which local wind has been held as an 

 important factor in beach erosion stems from the early reports of the 

 Beach Erosion Boardo These reports accorded a prominent place to dis- 

 cussion of the local wind and its probable effects = Today, when it is 

 believed that the nechanism of loss of beach is better understood than 

 previously, there is a notable tendency to assign to local wind a much 

 less important place as a factor in sand loss» 



Wind is believed presently to be the ultimate source of the energy 

 which, when expended on a beach, either directly as wind or indirectly 

 through the riBdium of surface water waves, causes transportation of sand 

 along the shore and the bottom, and ravages the land boundaries of the 

 water masso In the process of expending energy on the shore local winds 

 are recognized now as playing usually a relatively minor role o 



Investigators long have recognized the beach as the primary source 

 of supply for shore dunes and correctly identified local wind as the 

 eroding and transporting agent responsible for the dune formations » The 

 conditions requisite to erosion, or deflation of beaches by local winds 

 can be stated as 5 



1. An expanse of dry beach sand, of sufficient extent in 



the direction of wind movenent and so located with respect 

 to the surrounding topography as to permit sand transport 

 by a local wind system, 



2. The existence of wind in intimate proximity to the sand 

 surface 



This second condition appears at first glance to be trivial, however, 

 those familiar with beaches located adjacent to appreciable topographic 

 irregularities often have experienced absence of wind immediately con- 

 tiguous to the sand surface when local wind was present elsewhere « 



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