values were around 0.10 m ^ between those found for the main breakpoint bar 

 from the plunge point to the break point and from the break point seaward 

 (Part V). 



482. The location of the minimum transport rate x^ must be specified 

 to completely determine the transport rate distribution in the wave reforma- 

 tion zone. Once this point is known, the transport rate is calculated from 

 the exponential decay starting from the wave reformation point. The power 

 curve then connects the minimum transport rate thus determined with the 

 transport rate at the second break point. As waves reform, turbulence is 

 advected onshore with the waves, keeping grains in suspension and making them 

 available for transport. However, because the generation of turbulent motion 

 through wave energy dissipation decreases considerably, the transport rate 

 decreases correspondingly. Closer to the second break point on the seaward 

 side, the transport rate is expected to increase again, caused by the large 

 energy dissipation shoreward of the break point. Since the sand transport 

 capacity of a reformed wave is probably larger than for waves in the zone 

 immediately seaward of a break point, the point of minimum transport should 

 probably be located closer to the second break point than the point of wave 

 reformation. In the model, the location of the minimum transport rate in 

 zones of wave reformation was arbitrarily placed seaward of the second break 

 point one third the distance to the wave reformation point. 



483. In initial simulations of multiple bar formation, the inshore bar 

 typically formed too close to the main breakpoint bar, compared with measured 

 beach profiles from the LWT experiments. This was caused by rapid shoaling in 

 the model after wave reformation, making the break point form too far seaward, 

 since wave energy dissipation drastically changed as waves reformed and 

 shoaling became dominant. Because wave reformation is a gradual phenomenon, 

 it was believed that successive turn-off of energy dissipation would provide a 

 more adequate representation of what actually happens in this zone. The turn- 

 off is implemented in the numerical model by decreasing the wave decay 

 coefficient k exponentially with distance from the wave reformation point. 



A decay coefficient of 0.025 m'^ in the exponential damping function proved 

 sufficient to accurately describe the location of the second bar. 



203 



