of a floating breakwater acted on by several wave 

 trains from different directions and to measure 

 stresses in its mooring cables. Tests were per- 

 formed at a 1 to 24 linear scale. The efficiency 

 of the breakwater in reducing wave heights drops off 

 rapidly with an increase in wave period beyond 8.5 

 (prototype) seconds or when the wave length approx- 

 imates the width of the breakwater section from front 

 to back. Forces required to hold the breakwater in 

 place against larger waves (greater than 9 to 10 feet 

 prototype) exceeded 200,000 pounds per anchor chain, 

 and prototype stresses in some of the braces and struts 

 exceeded present practical design limits. 



NO. 100 - October 1957 



II-A "Wave -Generated Ripples in Nearshore Sands" by Douglas L. 



B Inman 



C 



D A study of the occurrence of sand ripples generated by 

 wave action in the nearshore area has been made based 

 on observations by swimmers equipped with self-contained 

 underwater breathing apparatus. The wave length, crest 

 length, height and symmetry of the ripples were measured 

 and COTipared with size of the sand and with orbital 

 displacement and velocity of the wave motion generating 

 the ripples. In general ripple size increased with sand 

 size and, to a certain extent, with water depth. Ripples 

 in exposed areas were generally larger than those in 

 sheltered bays. Ripples were always present when the 

 orbital velocity was between about 0.3 and 3 feet per 

 second. 



NO. 101 - October 1957 



II-C "Dune Formation and Stabilization by Vegetation and Plantings" 

 E by Dr. John H. Davis 



F 



A discussion of the effectiveness of various plants in 

 dune formation and stabilization is presented. Methods 

 for establishing plantings are included. Also included 

 are performance records of several dune vegetation 

 installations in various parts of the country. A tabu- 

 lation of plants which are numerically important toward 

 dune stabilization in the United States and their fre- 

 quency of occurrence for various parts of the United 

 States coast is appended. 



Ill 



