34 
storms than during relatively calm summer wave conditions). The four different 
wave time series and repetitive model simulations were used to compute error 
bands at monthly intervals. The model predictions show that the observed losses 
from the Monmouth Beach region are reasonably well predicted using the 
GENESIS model. Following this analysis, another series of model simulations 
were performed to investigate the relative benefit of constructing a shore- 
perpendicular groin at the northern end of the beach fill. A groin with a length 
of 200 ft (61 m) was placed at the northern end of the hot-spot region 
(approximately the location of the existing Coastal Structure 44). Again, 
multiple simulations were performed using the four different wave time series to 
compute error bands around each of the predictions. The model results show 
that between 10 and 20 percent more material remains in the placement area if a 
groin is constructed at the northern end of the modeled reach. 
This estimate is specific to the idealized conditions modeled. Additional 
model simulations are recommended to optimize the groin length based on the 
desired berm equilibrium width within the Monmouth Beach area and to 
determine long-term downdrift impacts of the proposed groin. 
Summary and Conclusions 
Figure 27 provides a summary of the calculations performed in this task. 
The major conclusion of this task is that the observed losses from the Monmouth 
Beach region can be relatively well explained by considering the region as an 
independent or stand-alone beach-fill project and calculating the loss of material 
from the region because of longshore sand transport processes. A secondary 
conclusion is the finding that the construction (or extension) of a shore- 
perpendicular groin at the northern end of the Monmouth Beach has the potential 
to significantly reduce the loss of fill material from the region. In addition, the 
construction of the Contract 2 beach fill to the south should provide an updrift 
supply of sand that will reduce the severity of beach erosion within the hot-spot 
region. 
Chapter 4 Beach-Fill End Losses 
