Concurrent measurements of swash flow velocity and sediment transport
were obtained from a natural beach to develop a means for predicting s
ediment transport in the swash zone. Twenty-seven swash events were mo
nitored and the sediment load of each event was correlated to the flow
velocity for both the wave uprush and backwash. The sediment load dis
played a strong relationship with the time-averaged velocity cubed, co
nsistent with equations for both bedload transport and total load tran
sport under sheet flow conditions. Validation of the energetics-based
model of Bagnold (1963, 1966) revealed different constants of proporti
onality for wave uprush and backwash, with the uprush value being appr
oximately twice that obtained for the backwash. Similarly, validation
of a modified Shields parameter (to account for the effect of a slopin
g bed) also indicated different coefficients. The physical explanation
for the different constants of proportionality is that neither sedime
nt transport model adequately accounts for the disparate nature of the
two phases of the swash cycle. (C) 1998 Elsevier Science Ltd. All rig
hts reserved.