BUILDING TO BE PROTECTED 



.ORIGINAL SHORELINE 





EXPECTED TOMBOLO FORMATION^ \v>/£vt;^>»\y 



NET LONGSHORE DRIFT 



^>i*v::j bo>:-'' : --;,*: 



MATION^ N-.*^ ; 'V.i''.: - A ••.'"'; ' 



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Figure Bl. Layout of design for a single tombolo 



protection along the entire 100 m of the site. Also to ensure tombolo for- 

 mation and to promote the survival of the tombolo during storm events, the 

 breakwater should be impermeable and have a crest high enough to prevent 

 significant overtopping by storm waves. The crest elevation required to 

 prevent overtopping during a significant storm with accompanying surge is 

 determined for H. = 4.0 m and d = -4.0 m MSL using Chapter 7 of the SPM. 

 Figure Bl shows the site plan of the project and the expected adjusted 

 shoreline. 



Problem 2: Design of a Series of Unconnected Salients 



Problem 



4. A submerged rock intrusion partially blocks the predominant long- 

 shore transport to a beach which contains the remains of a Civil War fortifi- 

 cation and is a National Historic Landmark and park facility (Figure B2) . The 

 shoreline is responding by assuming a spiral shape. Retreat downdrift of the 

 rock outcrop has already inundated much of the battlements and the remaining 

 ones are threatened. The beach is a popular recreation area. The shore re- 

 quiring protection is approximately 750 m long. The wave climate has a dis- 

 tinctive seasonality. The affected shoreline accretes approximately 20 m 

 beyond the normal winter beach during the summer when the waves are out of the 

 southeast. It is desirable to avoid any adverse impact to adjacent beaches 

 which are not owned by the park. If the shore fronting the historic site is 

 restored to a general alignment with the updrift beach, sediment can be 



B2 



