PREFACE 



This report is published to provide coastal engineers with guidelines for 

 the design of weir-jetty sand-bypassing systems. A weir jetty is only one of 

 several bypassing schemes that merits consideration when there is concern about 

 erosion downdrift of a jetty project. The report does not intend to suggest 

 that weir jetties are the best solution to all bypassing problems but simply 

 presents a series of design goals and "rational" procedures to help evaluate a 

 weir- jetty system against those design goals. It should provide some design 

 techniques that will allow the designer to make judgmental decisions regarding 

 such factors as weir height, length, orientation, etc. Since the design of a 

 bypassing system depends critically on local conditions, absolute values for 

 these variables cannot be set. The work was carried out under the coastal 

 structures program of the U.S. Army Coastal Engineering Research Center (CERC). 



This report is one of a series of reports to be published to form a Coastal 

 Engineering Manual. 



The report was prepared by Dr. J. Richard Weggel, Chief, Evaluation Branch, 

 under the general supervision of N. Parker, Chief, Engineering Development 

 Division. Many of the ideas or concepts expressed in the report did not orig- 

 inate with the author but were gleaned from discussions with other coastal 

 engineers. For example, Dean M.P. O'Brien (1976) originated the concept of how 

 an ideal weir-jetty system should perform so that it bypasses only the net 

 longshore transport, and Dr. R. Dean developed the idea that the quantity of 

 sand that needs to be stored in the updrift beach fillet depends on the timing 

 and duration of transport reversals. Some of the concepts have been extended 

 by the author and analysis methods suggested; any erroneous interpretation of 

 the original concepts lies wholly with the author. 



Comments on this publication are invited. 



Approved for publication in accordance with Public law 166, 79th Congress, 

 approved 31 July 1945, as supplemented by Public Law 172, 88th Congress, 

 approved 7 November 1963. 



SD E. BISHOP 

 Colonel, Corps of Engineers 

 Commander and Director 



