beach profiles in time. The equation of mass conservation was integrated from 

 successive beach profile surveys, and an average net transport rate over the 

 studied time interval was obtained. The technique of determining the distri- 

 bution of the net cross -shore transport rate from consecutive profile surveys 

 has been employed in other studies (for example, Hattori and Kawamata 1981; 

 Watanabe, Riho , and Horikawa 1981; Shimizu et al . 1985). A classification of 

 transport rate distributions for LWT results was proposed by Kajima et al . 

 (1983a) based on a beach profile classification by Sunamura and Horikawa 

 (1975) who used data from experiments with a small tank. 



302. By determining the transport rate from profile change, an average 

 net distribution of the cross -shore transport rate is obtained for the elapsed 

 time between two surveys. An alternative method of acquiring information on 

 the transport rate is measurement of the sediment concentration and fluid 

 velocity field. Sawaragi and Deguchi (1981) and Deguchi and Sawaragi (1985) 

 measured sediment concentrations in small-scale laboratory experiments and 

 obtained concentration profiles at selected locations across the beach 

 profile. Vellinga (1986) and Dette and Uliczka (1987b) made similar measure- 

 ments of concentration profiles in experiments performed with large tanks and 

 waves of prototype scale. 



303. The average net cross-shore transport rate may be obtained by 

 integrating the equation of mass conservation between two beach profiles in 

 time. The transport rate q(x) across the profile is thus calculated from 

 the mass conservation equation written in difference form with respect to time 

 as 



X 



q(x) = -—^ [ (h2 - hi) dx (18) 



X„ 



where 



^1.^2= times of profile surveys 



Xq = shoreward location of no profile change, where q(Xo) = 

 hj , h2 = profile depths at survey times 1 and 2 



304. To evaluate the transport rate numerically, measured profiles used 

 in this study where approximated by a set of cubic spline polynomials (see 



118 



