Figure 13 shows the mean water level during the run, position of the traps, 

 bottom profile, vertical distribution of the flux, and cross -shore distribu- 

 tions as determined from Equation 3. Figure 13 replaces similar figures 

 presented by Kraus and Dean (1987) by incorporating trap efficiencies and 

 correcting for a calculation error. 



47. Considerable information is contained in Figure 13, some of which 

 has been discussed by Kraus and Dean (1987) and Kraus, Gingerich, and Rosati 

 (1988). It is clear that transport on and near (within 9 cm of) the bed 

 predominated in these experiments. The magnitude of the longshore flux, 

 represented by the length of the histograms, decreased sharply above the 

 bottom streamer. At some traps, a nonzero flux is observed above the mean 

 water level; this material was collected as it moved alongshore during periods 

 of higher water elevation and in wave crests as they passed by the traps. It 

 is also noted that the shape of the vertical distribution is essentially 

 independent of position in the surf zone, i.e., irrespective of whether a trap 

 was located in the inner, middle, or outer surf zone', or at the inner bar or 

 trough. An irregular vertical distribution is rarely seen (i.e., a distribu- 

 tion with a shape other than monotonically decreasing) . At the two runs with 

 a trap located seaward of the mean breaker line (positioned just seaward of 

 the region of visibly significant breaking waves), a relatively small amount 

 of sand was collected, clear evidence that the longshore sand transport rate 

 drops off sharply seaward of the breaking wave zone . The operator of the trap 

 located seaward of the breaker line noted a significant longshore current at 

 that position, and the streamers remained extended. Evidently, the absence of 

 turbulence and associated sediment entrainment produced by breaking waves 

 resulted in a low transport rate compared to the surf zone rates. 



48. Cross-shore distributions are shown in the lower portion of 

 Figures 13a-h. On the basis of multicolor sand tracer field experiments, 

 Kraus et al . (1982) found that even on near -planar profile shapes, the cross - 

 shore distribution can take at least four different forms: a single peak in 

 the outer surf zone, just shoreward of the wave breakers; a single peak in the 

 inner surf zone ; peaks in the inner and outer surf zone ; and a uniform flat 

 shape (very broad peak) across the surf zone. In the present experiments, 

 discounting small peaks as being within the range of measurement variability, 



42 



