716
Stauble and Tabar
dies. The reef structure was placed at between 2.1 and 2.4
Shoreline Response
m ( 7 and 8 ft) MLW. A geotextile fabric underlayment
Shoreline response was measured in all six studies by mea-
was also used on this instillation for scour protection, but the
suring the change in lateral position of a datum elevation
thickness was doubled as compared with the Avalon project.
from beach profiles measured over the monitoring period
A 1.3 m (4.3 ft) wide polyethylene geomattress filled with 6.1
from a fixed benchmark. The mean high water datum ele-
to 10.2 cm (2.4 to 4 inch) stone was placed along both the
vation crossing was used to represent the shoreline position
landward and seaward side of the base to mitigate for scour
along the profile at the P.E.P. Reef projects. The Beachsaver
based on the experience with the Avalon installation.
projects used the MLW datum at Cape May Point and 0
The Beachsaver Reef placed at Belmar/Spring Lake was
NGVD datum at Avalon and Belmar/Spring Lake crossing as
also installed at the seaward end of a groin compartment
a shoreline change indicator.
with a width of around 335 m (1,100 ft). The reef was at-
The Dupont Property P.E.P. Reef installation included a
tached to the two groins about 128 m (420 ft) seaward of
MLW, at 2.3 to 2.4 m ( 7.5 to 8 ft) MLW depths. A 6.1
north (updrift) and south (downdrift) control area. Two years
after placement of the P.E.P. Reef at the DuPont Property in
m (20 ft) gap was left to enable a 0.91 m (3 ft) diameter ocean
Palm Beach County, the shoreline change was variable but
outfall pipe buried 0.91 m (3 ft) below the bottom to extend
essentially landward of the pre-project shoreline. The irreg-
offshore, perpendicular to the shoreline. The gap was filled
ular shoreline was a function of the pre-existing groins and
with a stacked geomattress configuration up to the crest el-
seawalls.
evation of the Beachsaver Reef. Reef crest elevations of be-
tween 0.7 to 1.16 m ( 2.3 to 3.8 ft) MLW were mea-
The Midtown Palm Beach site included two control areas
north and south of the P.E.P. Reef. Over the 3 years of mon-
sured after placement at this site. The same double thickness
itoring the updrift north control shoreline position was mixed
geotextile fabric underlayment as was used at Cape May
with an net average recession. The highest long-term shore-
Point, was used on this instillation for scour protection.
line retreat was measured in the P.E.P. Reef area. The larg-
Again, the same polyethylene geomattress filled with stone
est recession was measured in the area at the south end of
was placed along both the landward and seaward sides of the
the P.E.P. Reef and the northern part of the downdrift south
base to also mitigate for scour. A truck haul beachfill was
control area. Overall, the south control area shoreline also
placed in the groin compartment after placement of the Reef.
retreated landward.
From the experience gained with the long single line Mid-
At Avalon, New Jersey, there was initial seaward move-
town Palm Beach installation of the P.E.P. Reef, the Vero
ment of the shoreline in response to a beach fill placed at the
Beach installation was modified to contain eleven segments
same time as the Beachaver was installed. The monitoring
ranging in length from 51 to 93 m (168 to 304 ft). They were
area included the reef and southern control area. After two
placed in an alternating onshore/offshore configuration with
years, profiles behind the inlet jetty-attached northern end
gaps between each segment, covering a total alongshore
of the Beachsaver Reef showed more stability than the pro-
length of 914 m (3,000 ft). This alternating placement was
files to the southern open end of the reef and southern control
approximately 61 m (200 ft) from the beach for the inshore
area. The semi-enclosed northern profiles were approximate-
segments and 76 m (250 ft) for the offshore segments. Design
bottom elevations were 2.1 m ( 7 ft) for inshore units and
ly 15.2 m (50 ft) wider than the pre-fill beach, while the more
2.7 m ( 9 ft) for offshore units. Reef crest elevations av-
open southern beaches returned to a pre-fill width.
eraged between 1.37 m inshore to 1.83 m offshore ( 4.5
At Cape May Point, New Jersey, the shoreline response
to 6.0 ft) NGVD or 0.90 to 1.36 m ( 2.95 to 4.45 ft)
was measured by the movement of the MLW contour line
from the beach profiles. The analysis was divided into three
MLW after settlement. Some of the units were placed on a
cells, with Cells 2 and 3 related to the two groin compart-
sandy bottom and some were placed on a thin sandy veneer
ments fully enclosed on the seaward end by the Beachsaver
over the natural hardbottom, which outcrops just seaward of
reefs and Cell 4, a open groin compartment, as a control area
the reef installation, which accounted for the differential set-
on the west. In the two-year monitoring period, the shoreline
tling. Various existing seawalls were on the backshore.
in the eastern-most compartment (Cell 2) moved seaward on
average 13.4 m (44 ft), while Cell 3 had a shoreline seaward
Performance Parameters
movement on average of 4.6 m (15.13 ft). The control Cell 4
to the west migrated landward an average of 4.6 m (15.13 ft).
The monitoring of the six installations of the shallow-crest-
The trend was for more landward shoreline movement to the
ed prefabricated breakwaters has allowed a cross comparison
downdrift western direction.
of performance parameters. Table 8 summarized the perfor-
The Belmar/Spring Lake placement was also completely
mance parameters of each breakwater installation. In at-
across a groin compartment. Fill material was also placed on
tempting to meet the objectives, did the reef structures sta-
the upper beach of the Beachsaver reef compartment only. A
bilize the shoreline? Was sediment retained behind these
north and south control area of one groin compartment on
units? Did settlement of the units cause any change in their
either side was also monitored. The 0 NGVD elevation shore-
performance? Was there any scour caused by the placement
line moved landward approximately 15.2 m (50 ft) over the
or breakwater configuration? How much wave attenuation
one year monitoring period. The north (downdrift) control
was afforded by the use of these types of structures as shore
protection devices?
area compartment (which did not receive any fill) shoreline
Journal of Coastal Research, Vol. 19, No. 3, 2003
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