us, and Japanese structures. Given a desired salient length in the on- 

 offshore direction (measured from original shoreline) X^ , and a dimension- 

 less breaker distance Xy^/X , where X^ is the distance from the original 

 shoreline to the mean breaker line, the recommended ratio L^/X can be 

 graphically determined (Figure 2). 



19. Several relationships are also presented for determining tombolo 

 size in the equilibrium state, based on the field data of Inman and Frautschy 

 (1966), Toyoshima (1976), and Nir (1976) (Figure 3). Given project variables 

 L^ , X , and beach slope I , the following parameters can be estimated: the 

 volume of sand trapped in the tombolo Q , length of tombolo in alongshore 

 direction (measured at structure) Lj , and area of tombolo Aj . 



Shore Protection Manual (SPM) (1984) 



20. Based on the pattern of diffracting wave crests in the lee of a 

 breakwater, the US Army Corps of Engineers' Shore Protection Manual (SPM 1984) 

 recommends that the structure length be less than the distance offshore to 

 inhibit tombolo formation: 



— - < 1.0 tombolo formation prevented (8) 



This structure-distance ratio usually allows diffracting wave crests to 

 intersect in the shadow zone of the structure prior to undistorted wave crests 

 reaching the adjacent beach. For normal wave approach, the approximate 

 location of the salient apex is the intersection of the diffracting wave 

 crests as they reach the shoreline. 



21. The SPM recommends the following limit to ensure tombolo formation: 



— ^ > 2.0 tombolo formation certain (9) 



Dally and Pope (1986) 



22. Dally and Pope (1986) recommend limits of the structure-distance 

 ratio based on the type of shoreline advance desired (either nonuniform, where 

 salients or tombolos occur, or uniform, in which an equal advance of the beach 

 occurs) , and the length of the beach to be protected. For nonuniform 



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