Alongshore location (m)
Figure 80. Beach morphology after nearly 10 hr of wave activity for the spilling-
breaker case (elevations are in meters)
Figure 81 shows the cumulative change in beach elevation for this same case
during the 10 hr of exposure to the same spilling-type breaking waves. Elevation
changes are given in meters. The loss of sand from the updrift end of the beach
is quite evident; beach elevation decreased by 0.1 m or more in the high-loss
areas. Figure 81 clearly shows the alongshore extent of the perturbations both in
the offshore region and along the beach, and how the extent varies with cross-
shore position. The figure shows that the inshore portion of the profile (yellow-
shaded region) continued to lose between 0 and 2 cm of elevation, while the
offshore bar gained sand at about the same rate (green-shaded region). This
appears to be a consequence of the continued approach toward an equilibrium
beach condition, albeit at a much slower rate that that observed in the early stages
of profile evolution. The maximum bottom elevation increase, associated with
accretion along the downdrift boundary, was about 0.04 m.
136
Chapter 10
Longshore Sediment Transport Experiments
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