at +1.2 in MSL, and the tide range is 0.5 m. A 69,000-cu-m artificial fill 

 placed shortly after construction moved the shoreline to within an estimated 

 50 m of the breakwater. A salient formed which nearly connected to the struc- 

 ture by August 1966. This condition is illustrated in Figure 9. In December 

 1969 a severe storm damaged the breakwater and beach fill but both were 

 repaired by late 1970. 



Segmented Detached Breakwaters 



20. The concept of a segmented detached breakwater has been used exten- 

 sively in other countries, creating a broad experience base (Lesnik 1979). 



One of the best documented projects is the series of shallow-water "artificial 

 headlands" at Singapore (Figure 4), although other projects exist in Italy, 

 France, Israel, and Denmark, to name just a few. Segmented offshore break- 

 waters have been used for almost 30 years in Japan (Toyoshima 1972) . The 

 Japanese have developed a construction and general configuration plan which is 

 functioning successfully at more than 20 different sites. Typically, Japanese 

 segmented detached breakwaters are built fairly close to shore, which would 

 normally cause development of a tombolo. However, these breakwaters have no 

 core and are fairly permeable; therefore, inhibiting tombolo formation. 



Winthrop Beach, Massachusetts 



21. The Winthrop Beach project (Figure 10) was the first segmented de- 

 tached breakwater in the United States. The breakwater was built for shore 

 protection; however, gaps were incorporated into the project plan to permit 

 boat traffic. Completed in 1935, it consists of five 100-m-long impermeable 

 rubble-mound segments separated by 30-m gaps. The total length of the break- 

 water is 625 m. The structure is shore-parallel and was constructed 300 m 

 from a seawall at an average water depth of 3.8 m. The structure crest is at 

 +4.1 m MSL. The region has a normal tidal range of 2.7 m and a spring range 

 of 3.4 m. This large tidal range has important ramifications in the shoreline 

 response. An irregularly shaped, multiple tombolo is exposed at low tide 

 (Figure 10a) , when the structure is only 150 m from the updrif t shoreline 

 alignment. However, at high tide (Figure 10b), only an unconnected bulge is 

 visible above water. These features have been relatively persistent since 

 1937. Two possible scenarios could be used to explain the presence of 



20 



