configuration was more sensitive to changes in the K2-value. Thus, consideration
of Cases 1 and 3 in the calibration and verification procedure facilitates
determination of optimum values of K1 and K2. The closure depth for GENESIS
was taken to be 24 cm by inspection of beach profile change in the physical
model. A longshore grid interval of ∆x = 25 cm and time step ∆t = 18 sec were
specified in an explicit solution scheme version of GENESIS. In the DBW
configuration, after numerical testing, transmission coefficients (Hanson and
Kraus 1990) were taken as 0.05, 0.05, and 0.08, respectively, from left to right .
For verification of GENESIS, shoreline positions at 4 and 18 hr were
examined in Cases 1 and 3 as shown in Fig. 3. Values of the transport parameters
in shoreline response between cases are well described, as is the offset in
shoreline position as responds to wave direction. The tilt in trend of the shoreline,
as shown by the positions of the tips of the salients, results from the lateral
boundary conditions, producing complete sand starvation on the right side and
complete impoundment on the left side. The magnitude of the change is also well
reproduced. The center and left portions of the shoreline show good agreement
between the physical and numerical models. However, in the right-hand portion
of the basin the agreement is more qualitative than quantitative, believed to owe
to existence of a complex wave field near the basin wall in the physical model.
1.0
Meas. groin
Meas. DBW
Calc. groin
Calc. DBW
0.0
-1.0
0
4
8
12
16
Distance Alongshore (m)
Fig. 3. Result of model verification of Cases 1 and 3.
Case 4 was simulated with K-values left unchanged. The offshore wave
height was measured at hourly intervals. Based on the two readings, a linear
variation in wave height alongshore was calculated every hour to serve as input
for the simulations. The wave transformation from the offshore region to
breaking was calculated internally in GENESIS. The measured breaking wave
height at the beginning of the test was compared to that calculated by the model.
5
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