CE Case 101 



Distance Offshore (m] 



measured 



Figure 84. Simulation of berm formation and growth 



zone of erosion in the tank occurred more seaward than the location predicted 

 by the numerical model . 



523. In other model simulations of accretion, the zone of fully broken 

 waves became very narrow as the break point moved onshore and the waves 

 directly struck the berm or foreshore. The length of the broken wave zone 

 eventually decreased to only one calculation cell, and a transport rate 

 equation based on energy dissipation per unit volume was no longer realistic. 

 In these cases, the transport rate calculated from the energy dissipation was 

 reduced. If no reduction was employed, very local erosion and accretion 

 occurred in the vicinity of the shoreline, giving rise to numerical instabil- 

 ity. The value of the reduction factor was typically around 0.2 in these 

 cases. This problem might have been circumvented by using extremely small 

 spatial and temporal steps. 



222 



