in parentheses in equation (9) has been shown to be constant (see eq. 6) 
seaward of the breaker line; therefore, subscript b may be replaced by i 
which represents any point seaward of the breaker line. Making this change, 
using. equation (5), and letting Hims equal H for monochromatic waves, 
equation (9) becomes 
2 
= (2gH” We 
Pop ( 8 oy cosa i sino, (10) 
The Shore Protection Manual (SPM) (U.S. Army, Corps of Engineers, Coastal 
Engineering Research Center, 1977) provides a term similar to Pe, except 
that the wave height used is the significant height, H,- The term, called 
the longshore energy flux factor, is defined as 
ipa ) 
P = 3 C cosa sina b (11) 
Pp, is derived in Galvin and Schweppe (1980). The relationship between 
Here and H, has been shown in Longuet-Higgins (1952) to be 
2 = 972 
Hei yeh (12) 
assuming a Rayleigh distribution of wave heights as well as a number of other 
conditions. Therefore, 
P 
P 
ns 
Ni 2 aD (13) 
Since Po, and P are essentially the same terms, this report uses the SPM 
terminology and refers to Pp} as the longshore energy flux factor. 
3. Longshore Transport Rate. 
The longshore transport rate, Q, given in the SPM in units of volume per 
unit time, is also commonly shown as_ I with units of immersed weight per 
unit time. The relationship between the two is 
Mn (Go) 119) E24 (14) 
where p, is the mass density of sand and a" the ratio of sand volume to 
total volume of a sand deposit, which takes into account the sand porosity. 
For discussions of equation (14), see Komar and Inman (1970) and Galvin 
(1979). Since the laboratory tests described here measured I, directly, 
this term is used in most of the data analysis. 
14 
