Sverdrup and Munk succeeded in establishing a fundamental equation relating 

 wind action to virave action, and showing that the energy content of the waves 

 generated depends primarily upon the wind velocity, the wind fetch, and the 

 wind duration. 



Waves forecast by the Sverdrup-Munk relationship have bean shown by 

 comparative observation to approximate reasonably well natural conditions, 

 thus confirming their theoretical concepts c It can be concluded that the 

 waves reaching a shore are, in m_ost instances, due to the net effect of one 

 or more wind systems transferring energy to the water, with the wave motion 

 serving as a collecting and transporting rtediura conveying the net energy con- 

 tained in the waves to ths shore. 



At the shore interface wave motion can no longer exist and the wave 

 energy built up over long intervals of time and space must be dissipated 

 abruptly o A large part of the energy is believed to be lost in the turbu- 

 lence of the breaking wave, in the pick-up and throwing into suspension of 

 bottom or beach material, in impact, and other losses, the remainder being 

 lost in the rush of the broken wave, carrying its load of suspended sand, 

 up the beach slope „ This is an ideal situation for the erosion and trans- 

 port of large quantities of sand or beach material o Waves commonly approach 

 the shore face at an angle and there is a resulting component of motion of 

 sand and water along the shore, giving rise to the well-kn.own littoral 

 transport of sando 



The annual rate of loss of sand by littoral transport due to wind- 

 generated waves varies widely in different situations, the maximum known • 

 to the author occurring south of Port Hueneme, California, and approximat- 

 ing 1,000,000 cubic yards <, This rate is some twenty time the estimated loss 

 due to local wind action in the same general area„ In other areas, such as 

 the south Florida coast losses due to local wind are not discernible while 

 littoral transport approximates 250,000 to 270,000 cubic yards annuallyo 



The effects of wind action on water in causing wind-generated currents 

 and wind set-up or depression are considered to be negligible in the usual 

 shore problem in comparison with the effects discussed above., 



It should not be presumed that the effect of wind on beaches is wholly 

 destructive o In fact the destructive effects of local winds in denuding 

 beach areas beyond the range of normal wave and tide action can be turned 

 to good purpose by management of the wind-transported sand„ The use of 

 planting and sand fences to build dunes on or immediately adjacent to the 

 landward portions of a beach is an effective means of conserving and stock- 

 piling sand against the day of unusually destructive storm wave or tide 

 actiono This conservation practice has been notably successful in rebuild- 

 ing and maintaining the protective dune ridge of the south shore of Long 

 Island o In the September 1938 hurricane that devastated much of the New 

 York and New England area it was the dune ridge built naturally by local 

 wind action and acting as a dike that prevented engulfment of the Great 

 Barrier beach of Long Island by the seao Further, the sand of the dunes, 

 once lost from the beach, was returned to the beaches by the waves to 

 preserve the famous strand characteristic of this areao Careful management 



22 



