708
Stauble and Tabar
Monitoring Program
6). Placement and measurement of the scour rods was done
by divers. Elevation data was also collected at 2.1 and 2.7
A four-year monitoring program funded by Indian River
m ( 7 and 9 ft) NGVD contours derived from profile survey
County was conducted by the US Army Engineer Research
data in the north and south control areas to compare with
and Development Center, Coastal and Hydraulics Laboratory
elevation changes at P.E.P. Reef locations. Four scour rods
(CHL) to provide an independent evaluation of the effective-
were placed in the vicinity of the north end of P.E.P. Reef
ness of the P.E.P. Reef system (STAUBLE, 2002). This moni-
Segment A. Six rods were deployed around the south end of
toring program, which began with a pre-installation survey
Segment A, along Segment B and at the north end of Seg-
in May 1996, included: quarterly beach profile surveys to as-
ment C. Another set of 10 rods was placed in the center of
sess shoreline and sand volume change; multiple wave gage
the project between Segment F, G and H (near station 2 and
deployments (year 1 and 2) to measure wave transmission;
3 wave gages) to monitor the center of the project. The final
breakwater settlement monitoring (year 1) to determine set-
5 scour rods were placed at the south end of the project,
tlement of concrete units on sand and hardbottom substrate;
around unit J and 4 scour rods were placed at the south end
and scour rod measurements (year 1 and 2) to assess scour
of unit K (the southernmost unit in the project). No scour rod
adjacent to P.E.P. Reef segments, as well as an analysis of
measurements were scheduled during 1999 or in June 2000,
pre-project historical shoreline change conditions. Due to
but profile surveys were used to measure a pronounced scour
high tropical storm activity in the summer and fall of 1999
trough that was always present on the landward side of each
and the rapid post-storm beach sand recovery (in the third
P.E.P. Reef segment. A scour trough was also measured on
year), an anomalous condition was created for the final sched-
the seaward side of the reef segments, but the seaward side
uled survey conducted in December 1999. A newly designated
scour trough was prominent on some surveys and was filled
final survey was taken in June 2000, at which time it was
in on other surveys (STAUBLE, 2002).
thought that the beach would return to a more typical con-
P.E.P. Reef unit crest elevations were measured in con-
figuration. The purpose of the program is to evaluate the ef-
junction with the as-built beach profile survey directly follow-
fect of the P.E.P. Reef on profile and area volumetric changes,
ing unit placement on 16 August, 1996. Settlement was mea-
wave attenuation, structure stability and shoreline response.
sured by placing a survey rod on the top of the reef unit. This
Beach profiles were collected by Morgan and Eklund, Inc.,
structure measurement was made again in December 1996
and scour and wave attenuation studies were provided by the
thru February 1998 to assess changes in each reef unit's crest
Florida Institute of Technology, Division of Marine and En-
elevation during the first year (Table 6). Biofouling was prev-
vironmental Systems.
alent on the reef segments and this growth was scraped off
A total of 40 profile lines were established using DEP Mon-
before settlement measurements were made so that the rod
uments R-75 to R-89 plus supplemental profile locations be-
was placed directly on the top of the concrete of each unit.
tween the DEP monuments (Figure 23). DEP monuments are
This procedure gave an accurate measure of settlement of
spaced around 305 m (1,000 ft) apart, so supplemental mon-
each unit. No structure measurements were scheduled for
uments were spaced 61 m (200 ft) between lines within the
1998 and 1999. Settlement measurements were not taken in
limits of the P.E.P. Reef to provide coverage of each reef unit.
conjunction with the final June 2000 survey. However, ele-
Control profiles were established up to 1,524 m (5,000 ft)
vation measurements of the fouled top of the P.E.P. Reef were
north and south of the breakwater terminus, with a 152 m
measured as part of the beach profile survey. This method is
(500 ft) spacing of supplemental profiles outside of the P.E.P.
not as accurate for measuring settlement, as it did not mea-
Reef limits. Surveys extended out to between 457 m (1,500
sure the top of concrete. The survey rod was simply placed
ft) and 1,067 m (3,500 ft) seaward of the baseline on all pro-
on top of the marine growth on the P.E.P. Reef crest. Com-
files. This was well seaward of the P.E.P. Reef position. The
parison was made between the elevation of the clean P.E.P.
wading portion of the profile was collected with the standard
Reef units taken during the August 1996 profile survey and
rod and tape method. The nearshore survey was collected by
the June 2000 survey (which included biologic growth) to give
boat with a fathometer. An overlapping area in the nearshore
an approximate measure of the elevation change of the unit
was collected by both methods to calibrate the fathometer
top between immediate post-installation and the final 46-
survey and provide a match for continuous cross-shore profile
month survey. Settlement of each individual unit depended
coverage. All profile surveys extended seaward of the natural
on unit placement relative to the natural hardbottom. Where
hardbottom reef, onto a natural sand bottom. The surveys
the hardbottom was near the surface on initial installation,
show little to no change in the bed elevation in this offshore
scour resulted in the unit settling to the top of the rock. Some
area over the entire monitoring period. A potential error es-
units became perched on the natural rock ledge and some
timate in determining sediment volume changes at hardbot-
units ended up on an angle over the edge of the rock ledge.
tom locations is estimated to be 1.1 cu m/m2 ( 0.13 cu yds/
Other units settled into a sand substrate, where hardbottom
ft2) (length of shoreline/cross-shore distance). This value was
was not near the surface (STAUBLE, 2002).
determined by comparing the volume differences at hardbot-
Aerial photography was taken for the entire project length
tom locations between several profiles over the study period
in 1993 (used as a pre-project base map) and annually be-
(STAUBLE, 2002).
tween 1996 and 1999 (Table 6). No photography was flown
A total of 36 scour rods were placed and maintained at
in 2000, but an additional set was flow in 2001 after the of-
9 (22.8
strategic locations to measure scour at different segments
ficial monitoring ended. Color photography in 9
22.8 cm) format was flown to show the shoreline and nat-
and at the gaps between segments from 1996 to 1998 (Table
Journal of Coastal Research, Vol. 19, No. 3, 2003
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