Submerged Narrow-Crested Breakwaters
693
Figure 9. Cumulative change in volume by zone at Midtown Palm Beach, Florida (after Dean and Chen, 1996).
monitoring period with the addition of erosion immediately
side of the reef and flows alongshore until it reaches the end
to the south of the reef (DEAN and CHEN, 1995c). BROWDER
of the reef, where it is allowed to flow offshore. This induces
(1995) suggested that the large amounts of sand movement
flow, and along with the natural longshore current, causes
indicated that the reef structure was modifying the natural
sand to be transported to the end of the reef and redeposited
current patterns in the area. DEAN et al. (1994a) suggested
in a downdrift location away from the reef structure. Labo-
that the structure caused a pumping mechanism. Water and
ratory experiments with dye flow and drogue trajectories
possibly suspended sand are transported landward over the
around the elongated P.E.P. Reef structure indicate a struc-
reef and due to the presence of the reef in the water column,
ture-induced circulation that moves water and sand along the
the natural return flow of the wave induced circulation is
landward side to the ends of the structure (DEAN et al.,
interrupted. Some of the water is trapped on the landward
1994b).
Figure 10. Plan view of cumulative change in 36-month monitoring of nearshore volume between August 1993 and June 1995 (after Dean and Chen,
1996).
Journal of Coastal Research, Vol. 19, No. 3, 2003
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