lie in the range Ky = 0.5 K, to 1.5 K, (Kraus 1983). 
Numerical solution scheme 
92. GENESIS allows selection of either an explicit or implicit finite 
difference solution scheme. Because of the locally jagged nature of the proj- 
ect reach with its numerous, irregularly-shaped revetments, seawall, groins, 
and other structures, the implicit solution scheme was chosen to be run at 
6-hr intervals in order to minimize problems with instability. The program 
remained stable for all runs. 
93. Grid and boundary conditions. An alongshore grid axis was set 
parallel to the longshore axis of the wave refraction grid. In shoreline 
modeling, the axis along the trend of the shore is customarily denoted as the 
"x-axis," and the axis orthogonal to it and pointing positive offshore is 
denoted as the "y-axis." This convention was maintained. Grid spacing along- 
shore was set at 50 m, giving three shoreline cells per wave model refraction 
cell. The finer spacing in the shoreline model is necessary to adequately 
resolve shoreline features in groin compartments. 
94. The grid had to be extended well beyond the project area on both 
sides to obtain termination points that would provide adequate boundary 
conditions. The south boundary was placed at Shark River Inlet, and the north 
boundary was placed at the northern end of the Sandy Hook critical zone (cf., 
Part II). The south boundary condition did not allow sediment to be trans- 
ported north across the boundary except under high wave conditions, but did 
allow sediment to be transported south under those wave conditions indicating 
transport to the south. This boundary condition represents Shark River Inlet 
as an almost complete sediment sink. 
95. The magnitude of the longshore sediment transport rate within the 
grid area is controlled in part by the lateral boundary conditions. In the 
present case, the predominant transport direction is believed to be from south 
to north, and model results become sensitive to the boundary condition imposed 
on the south side, i.e., at Shark River Inlet. This boundary condition cannot 
be specified with certainty, however. Reconnaissance of the site indicated 
that the inlet does function as a sink of transported sediment due to the 
channel and jetties. 
96. From inspection of available shoreline data, it appeared that the 
northern end of the Sandy Hook critical zone had moved little over the past 
50 years. Therefore, a fixed beach boundary condition was implemented on the 
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