so that equation (4-26) gives 



d " 2E = 12 a^ = 2 (0.92) + 12 (0.34) « 5.93 meters (19.5 feet) 

 Also, equation (4-28) gives 



2i ^ «s50 \ (Wd^ )'•' = '-'' (I^-O^HSOOO (0 



.81 \ 0.! 

 0.0001) j 



« 44.7 meters (147 feet) 



(b) Calculate 



and 



o^ « 0.62 H = (0.62) (0.25) = 0.155 meter (0.51 foot) 



H .^ = H - 0.307 a„ = 0.25 - (0.307) (0.155) = 0.202 meter (0.664 foot) 

 s^U s n 



Equation (4-26) gives 



d = 2H ^„ + 12 a„ = 2 (0.202) + 12 (0.155) = 2.26 meters (7.43 feet) 

 s50 H 



Equation (4-28) gives 



^ ~- »s50 ^s {tO^Y'' = («-202) (7) (sooo^ioloOOuK ^ 



= 6.28 meters (20.6 feet) 



*************************************** 



The calculated results in this example appear fairly consistent with the 

 Figure 4-30 results based on interpretation of sedimentary structures. The 

 shoreface (or littoral) zone has an extent comparable to d , and the seaward 

 limit to detectable wave effects occurs at a water depth on the same order of 

 magnitude as d^ . 



(3) Other Approaches . Several suggested procedures for estimating a 

 seaward limit to effective sediment transport have considered forms of along- 

 shore bathymetry and of onshore-offshore profiles. 



The limit to the appreciably active nearshore sediment wedge might be 

 revealed at some localities by the seaward extent of water depth contours that 

 are parallel to a relatively straight shoreline. This limit could indicate 

 the maximum water depth for effective reworking of nearshore sediment by 

 waves, smoothing out bottom irregularities by sediment transport (Dietz, 

 1963). However, charted bathymetry along the U. S. Atlantic and Gulf of 

 Mexico coasts exhibits an irregular along-coast variation in the limit depth 

 to shore-parallel contours, not clearly related to varying wave climate 

 (Everts, 1978). 



Other approaches to seaward limit estimation have analyzed the geometry of 

 charted nearshore profiles by various methods (Everts, 1978; Weggel, 1979). 

 These suggested methods use a shape for the nearshore waveformed profile 



4-75 



