Elapsed Time (hr) 



CE Case 101 



Figure 42 . Decay of peak onshore sand transport rate 

 and a best-fit empirical predictive equation 



Magnitude of Net Cross-Shore Transport Rate 



334. In the LWT experiments, breaking waves caused sand movement that 

 changed the shape of the beach profile. Depending on the wave properties, 

 characteristics of net cross -shore sand transport are expected to vary in 

 various regions along the profile, at least in a morphological sense (Keulegan 

 1948). In regions of breaking waves, wave energy dissipation is large, 

 maintaining grains in suspension, and more material is transported than in 

 regions of nonbreaking waves. Also, the swash zone is governed by quite 

 different dynamics than the surf zone, even if breaking waves prevail in both 

 zones. Keulegan (1948) identified three regions where "the laws of transpor- 

 tation of sand" were expected to be different: from the point of impending 

 wave break to the point where wave reformation occurs, from the point of 

 impending wave break and seaward, and from the point of wave reformation to 

 the shoreline. 



136 



