Alongshore location (m)
Figure 81. Change in morphology after nearly 10 hr of wave activity for the
spilling-breaker case (elevation changes are in meters)
Plunging-breaker case
Figure 82 illustrates the condition of the beach after approximately 3.3 hr of
wave activity, in response to the plunging-type breaking waves and associated
longshore currents. This figure shows the bathymetric change that occurred. The
wave conditions were expected to produce a pronounced breakpoint bar, which
they did. These plunging wave conditions produced about 2.6 to 2.7 times more
longshore sand transport, compared to the spilling-breaker wave case; and the
cross-shore distribution of longshore transport was quite different. The plunging-
breaker case produced two peaks in the LST distribution, one at the breaker zone
and one in the foreshore. The spilling-breaker case produced a distribution in
which the magnitude of LST monotonically increased with increasing proximity
to the shoreline, reaching its peak value in the foreshore.
In many ways, beach changes observed during the plunging-breaker case
were similar to those observed for the spilling-breaker case; but there were some
differences. In the most offshore portion of the updrift end of the beach, a slight
erosion perturbation is evident in Figure 82, and it is confined to a relatively
short distance away from the edge of the beach. This same observation was
noted for the spilling-wave case.
137
Chapter 10
Longshore Sediment Transport Experiments
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