PREBREAKING ZONE 



Figure 43. Definition sketch for four principal zones 

 of cross -shore sand transport 



port in the zone of wave breaking through the sediment flux at its shoreward 

 boundary, but the governing transport processes on either side of the boundary 

 are quite different. Zone II corresponds to the breaker transition region and 

 is located between the break point and the plunge point. From the location of 

 the plunge point to the point of wave reformation, one specific region, Zone 

 III, is defined where the waves are fully broken and gradually decay (inner 

 region in hydrodynamic terms). In this region the energy dissipation of the 

 waves due to breaking becomes fully developed. If several break points occur 

 with intermediate wave reformation, several zones of type II and III will be 

 present along the profile. 



337. Transport conditions in the swash zone differ from those in the 

 surf zone, making it logical to define a fourth transport region. Zone IV. 

 Cross -shore sand transport in the swash zone is expected to depend mainly on 

 properties of the runup bore, local slope, and sediment characteristics. The 

 runup limit approximately constitutes the shoreward boundary for cross-shore 

 transport by waves. In regions between zones of breaking and fully broken 

 waves, where wave reformation occurs, the transport conditions are regarded as 

 similar to what prevails in the region seaward of the main breakpoint. 



338. In summary, the four transport zones are located as follows: 



a. Zone I: From the seaward depth of effective sand transport 

 to the break point (prebreaking zone). 



138 



