The development of adequate knowledge of these six elements of any 

 specific shore problem constitutes the beach erosion control study or the 

 study of the shore effects associated with navigational improvement o The 

 determination of how to develop the knowledge required constitutes the gen- 

 eral investigation and research activities of the Board » 



Coastal Physiog 



The shore line of the United States is characterized by a diversity of 

 shore line forms „ The New England shore line particularly north of Cape 

 Cod is found to be rather rugged vri-th diffs and headlands fronting directly 

 on the ocean and with rather short lengths of beaches caught between the 

 headlands o 



The Atlantic shore line from Cape Cod south and the Gulf beaches are 

 characterized generally by long imif orm beaches -vsith the adjacent topography 

 lying only a few feet above high tide. Frequently, these take the form of 

 barrier beaches j, separated from the mainland by salt water marshes or la- 

 goons „ The Pacific shore line shows some of the characteristics of both the 

 preceding types of shore line with long sweeping beaches broken by bold 

 headlands. 



The geologist tells us that the composition and origin of these beaches 

 and headlands started some two billion years ago when the molten mass of 

 the earth began to solidify and cool into igneous rocks o These original 

 igneous rocks have gone through various changes due to changes in weather ^ 

 environment 5, etcc, so that the form and characteristics of many of them have 

 greatly changed. After all the weathering^ frost action^ glaciation, hydra- 

 tion,, etc. we find that theiB are on shores several types of rocks and 

 minerals 5 the most abundant of which is quartz sand. The quartz reaches 

 the beach environment under the influence of gravity j, by wind action, or as 

 water-borne detritus o 



Natural Forges Affecting Beach Erosion 



■Changes of the shore or beach follow from na.tural physical causes 

 resulting from the interaction of tte land^, the sea^ and the atmosphere at 

 the shore or beach o Changes in the shore line are usxnlly the result of 

 sand movement due to the action of several mt-ural forces. These forces 

 result from wave action, tidal action, and ocean currents^ which act on 

 the shore in varying degrees depending on the coastal physiography. The 

 dominant force is the wind-generated ocean wave. These waves after being 

 generated by a wind disturbance _, may leave the area of the disturbance and 

 travel for hundreds or even thousands of miles before being interrupted by 

 a land mass. Most of ttie waves noted along our shores are generated by 

 distant storms. 



Tides and Cur rents 



The subject of tides has engaged the attention of mathematicians and 

 engineers for several centuries. The principal effects of the tides in 



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