690
Stauble and Tabar
Table 2. Monitoring for P.E.P. Reef at Midtown Palm Beach, Florida.
Year
Month
Profile Survey
Wave Data
Scour Studies
Events/Other Monitoring
1992
July
Pre-Survey
July/August
Initial Instillation57 units in south
area
August
Hurricane Andrew
1993
April
Survey
July/August
Complete Installation237 units north
and south of initial units
August
Post-Survey
Scour
September
Wave Gages
December
Survey
Scour
1994
March
Survey
Scour
June
Scour
July
Survey
September
Scour
October
November
Survey
Hurricane Gordon
December
Survey
1995
January
Wave Gages
March
Survey
April
Video Camera
June
Survey
Scour
to wading depth by standard rod and level techniques, and
expectations (MARTIN and SMITH, 1997). Further installation
in the nearshore by boat mounted fathometer. The quarterly
was postponed while performance and settlement criteria
surveys extended offshore to around 366 m (1,200 ft). The
were evaluated over the winter months on the existing units.
annual surveys were extended to 1,067 m (3,500 ft) offshore.
Little further settlement was measured four-months after the
DEP lines were only surveyed annually and extended 1,981
initial placement so the remaining 273 units were placed in
m (6,500 ft) seaward. Profile data provided information on
July and August 1993 (DEAN et al., 1994a). The total sub-
shoreline position change and volume change along the pro-
merged breakwater consisted of 330 units placed in a contin-
files. Settlement of the units was monitored by direct mea-
uous line parallel with the shore with one gap of 65.8 m (216
surement of the elevation of the north, middle and south crest
ft) spanning offshore communication cables.
of each reef unit. Scour at the base of the P.E.P. Reef units
Monitoring Program
was measured by installing 28 scour rods at the north, cen-
tral and south ends of the breakwater and on both the sea-
A comprehensive monitoring of the 1,273 m (4,176 ft) long
ward and landward sides. These rods were surveyed in and
project (including the gap) was done by the Coastal and
the sand elevation change was measured by a disk that could
Ocean Engineering Department of the University of Florida
move along each rod by divers. Scour rods were also placed
(details can be found in BROWDER et al., 1994; BROWDER,
in a north and south control area. Sand samples were also
1995; DEAN and CHEN, 1995a; DEAN and CHEN, 1995b and
collected annually in the vicinity of the breakwater (DEAN et
DEAN and CHEN 1995c). This monitoring program included
al., 1994a). Table 2 provides an overview of the survey peri-
wave data from two directional wave gages located landward
ods and reef installation dates.
and seaward of the breakwater to measure wave changes as
they pass over the units (DEAN et al., 1994a). The wave gages
Monitoring Results
were approximately 15.2 m (50 ft) on either side of the break-
water, with the landward gage in 1.9 m (6.1 ft) water depth
Shoreline Response
and the offshore gage in 4.1 m (13.5 ft) water depth. Seventy-
five beach profile lines were used to monitor the change in
Shoreline response was measured from the profile surveys.
sand elevation. Supplemental project specific benchmarks
The shoreline was defined using the change in the position
were established between the DEP lines for this project mon-
of the mean high water (MHW) line position. The study was
itoring (Figure 6). Eleven survey locations were within the
divided into three zones with a 610 m (2,000 ft) north control
boundary of the P.E.P. Reef starting on the north near DEP
area, a roughly 1,219 m (4,000 ft) P.E.P. Reef area and a 610
monument R-95. The rest were control survey locations, es-
m (2,000) southern control area. Shoreline change in the
north control area was mixed alternating between 15.2 m
tablished both north and south of the project to assess updrift
( 50 ft), with a net average recession of 2.84 m (9.31 ft) over
and downdrift effects as well as native profile changes. The
north control area covered 610 m (2,000 ft) north of the north-
the entire study period (Figure 7). Within the P.E.P. Reef
ernmost reef unit and the south control extended 610 m
zone, the overall shoreline change measured from the pre-
(2,000 ft) south of the southernmost reef unit. Most of the
installation survey in July 1993 to the final survey in June
lines were surveyed on a quarterly basis, from the benchmark
1995 measured an average of 7.86 m (25.8 ft) of shoreline
Journal of Coastal Research, Vol. 19, No. 3, 2003
Previous Page
