Reprint or republication of any of this material 

 shall give appropriate credit to the U. S. Army Coastal 

 Engineering Research Center. 



Limited free distribution within the United States 

 of single copies of this publication is made by: 



Coastal Engineering Research Center 

 5201 Little Falls Road, N.W. 

 Washington, D. C. 20016 



Contents of this report are not to be used for adver- 

 tising, publication, or promotional purposes. Citation of 

 trade names does not constitute an official endorsement or 

 approval of the use of such commercial products . 



The findings in this report are not to be construed 

 as an official Department of the Army position unless so 

 designated by other authorized documents. 



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