Tabic 4-7. Longshore Energy Flux.Pj , for a Single Periodic Wave in 

 Any Specified Depth. (Four Equivalent Expressions from 

 Small-Amplitude Theory) 



Equation 



(energy /time/distance) 



Data Required 

 (any consistent units) 



4-31 

 4-32 

 4-33 

 4-34 



2C^ ('/4 E sin 2or) 

 C (■/4E^sin2Q^) 

 K^C^ ('/4 E^ sin 2a) 

 (2C)(K|C„r'C^('/4Esin2a„) 



d.T.H.a^ 

 d.T,H„.a„ 

 T.H,.a,.a 

 d,T,H,a„,a 



no subscript indicates a variable at the specified depth 



where small-amplitude theory is valid 

 C» = group velocity (see assumption lb, Table 4-9) 

 C^ = deepwater 



d = water depth 



H = significant wave height 



T = wave period 



a = angle between wave crest and shoreline 



/ cos 0(, ' 



Kd = refraction coefficient »/ 



tf- \ cos a 



Table 4-8. Approximate Formulas for Computing Longshore 

 Energy Flux Factor, Pf , Entering the Surf Zone 



Equation 



(ft. -lbs. /sec. /ft. of beach front) 



Data Required 

 (ft.-sec. units) 



4-35 



32.1 Hj,5/2 sin lay 



Hb.ab 



4-36 



18.3 HjlHcosa^y* sin 2a^ 



Ho.«c, 



4-37 



20.5 T H^ sin a^ cos a^. 



T.H,,a,,at 



4-38 



100.6 (H^/T) sin Q^ 



T.Hfc,a, 



H^ = deepwater 



Hy = brc.ikcr position 



H = signific.int wave height 



T = wave period 



O = angle between wave crest and shoreline 



Sec Table 4-7 for equivalent small amplitude equations and 

 Tabic 4-9 for .issumptions used in deriving Pj from P„. 



4-97 



Figure A-1. Page 4-97 of the SPM, showing four 

 formulas for longshore energy flux, 

 P Q , and four formulas for longshore 



energy flux factors , P 



Is 



