of 15 m are considered. Where anomalous erosion occurs, the correction is
subtracted from the volume that accumulates in the trap; where accretion occurs,
the correction is added to the volume in the trap. All trapped quantities are
corrected in this manner.
Figures 93 and 94 show the total rate of LST, with and without these
corrections, for spilling- and plunging-breaker cases, respectively. Results for a
number of wave runs, or test cases, are shown in each figure. In each figure, all
tests involve the same wave forcing, and are shown in chronological order. Early
runs, T1a through T1g, and T3a through T3i_case 1, involve iterations to
determine the proper pump settings, and are not relevant to this discussion.
3500
no trap efficiency correction
with trap efficiency correction
3000
2500
2000
1500
1000
500
0
Figure 93. Total LST rates computed with and without corrections to account for
anomalous volume change adjacent to the downdrift boundary for the
spilling-breaker case
In Figure 93, run T1h is the first run in which the "proper" mean longshore
currents were pumped in all flow channels for the spilling-breaker case.
Subsequent runs, T1h_case1 through T1h_case4 were made for various purposes,
but with the same mean longshore current distribution as run T1h. Cases
T1h_case5 through T1h_case10, were made with nearly the same mean
longshore currents as cases 1 through 4, but currents were modified slightly to
correct for small changes in mean beach profile shape. Theoretically, the total
corrected transport rates for cases T1h through T1h_case4 should be the same,
and results for cases T1h_case 5 though T1h_case10 should be very similar,
perhaps with slight differences. It is important to note that the beach was rebuilt
prior to cases T1h_case 4 and T1h_case8.
149
Chapter 10
Longshore Sediment Transport Experiments
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