Submerged Narrow-Crested Breakwaters
715
shoreline and allow increased volume of sediment to be re-
tained shoreward of the structure. The third objective is to
not increase erosion or adversely modify coastal processes. Of
the six different deployments of this type of breakwater,
three in Florida were constructed using the P.E.P. Reef units
and three in New Jersey used the Beachsaver Reef units. The
individual reef units of both products had a similar shape and
dimensions. Each installation however, had localized differ-
ences in morphology, coastal processes and the influence of
other shore protection structures to provide unique condi-
tions at each site (Table 7).
Summary of Installations
The Dupont Property installation in the Atlantic Ocean at
Palm Beach County, Florida was a 168 m (552 ft) long con-
tinuous line, located 53 m (175 ft) offshore of the mean high
water line in about 2.4 m ( 8 ft) NGVD of water or 2.14
m ( 7.02 ft) MLW. The P.E.P. Reef, consisting of larger first
generation concrete units, was seaward of several short T-
groins and various seawalls and was placed on a sandy bot-
tom landward of any hardbottom. This configuration was de-
tached from any of the other shore protection structures.
The Midtown Palm Beach, Florida, installation in the At-
lantic Ocean some 579 m (1,900 ft) north of the Dupont prop-
erty was a larger structure, constructed in two phases with
a total length of 1,273 m (4,176 ft) of smaller second gener-
ation P.E.P. Reef units. It was placed in a continuous line
parallel with the shore with one gap of 65.8 m (216 ft) span-
ning offshore communication cables. The units were placed
around 76.2 m (250 ft) from the shoreline in 2.9 m ( 9.4
ft) NGVD of water or 2.6 m ( 8.4 ft) MLW. The shoreline
was also armored at this location with various seawalls land-
ward of the submerged breakwater. A natural hardbottom
beach rock outcropped around 229 m (750 ft) seaward of the
reef.
The first Beachsaver Reef was installed at Avalon, New
Jersey, in the Atlantic Ocean on the southern shore of Town-
sends Inlet. The 305 m (1,000 ft) long, submerged breakwater
was attached at its north end to the inlet south jetty. It ex-
tended to the southwest in a more or less shore-parallel di-
rection some 100 to 150 m (328 to 492 ft) seaward of the
shoreline, with its south end open to the ocean in 2.2 to
3.8 m ( 7.2 to 12.5 ft) MLW water depth. This installa-
tion used a thin geotextile fabric underlayment for scour pro-
tection. An additional polyethylene geomattress filled with
stone was placed along the southern 73 m (240 ft) of the land-
ward side of the base later in the monitoring period to miti-
gate for scour. A beach fill was also placed along this beach
at the time of installation.
The Cape May Point, New Jersey, Beachsaver Reef instal-
lation was placed across the seaward end of two groin com-
partments between 91.4 and 122 m (300 to 400 ft) seaward
of the MLW line in a high tidal current area at the entrance
to Delaware Bay from the Atlantic Ocean. Both reef com-
partments were around 137.2 m (450 ft) long and were con-
nect the seaward end of all three groins by capstone. The
objective was to provide protection for the two pocket beaches
between the three groins from scour by the strong tidal ed-
Journal of Coastal Research, Vol. 19, No. 3, 2003
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