Submerged Narrow-Crested Breakwaters
701
Monitoring Results
Shoreline Response
Shoreline response was measured by the movement of the
MLW contour line from the beach profiles collected at the
various survey intervals. The analysis was divided into three
cells related to the two groin compartments and the control
area on the west (HERRINGTON et al., 1997). The shoreline in
the eastern-most compartment (Cell 2) between the Lehigh
Avenue and Whilldin Avenue groins moved seaward on av-
erage 13.4 m (44 ft) between May 1994 and April 1996 as
illustrated by Profile C (Figure 18a). The compartment be-
tween the Whilldin Avenue and Coral Avenue groins (Cell 3)
had a shoreline seaward movement on average of 4.6 m
(15.13 ft) as seen in representative Profile G (Figure 18b).
The shoreline in control cell west of the Coral Avenue groin
migrated landward an average of 4.6 m (15.13 ft) as shown
in Profile L (Figure 18c). A trend of increased landward
movement to the west was evident in this study (HERRING-
TON et al., 1997).
Sediment Volume Response
The total volume change in each cell was measured by cal-
culating the average unit volume change between profiles col-
lected at two time periods and multiplying it the distance
between adjacent profiles, then summing over the entire cell
alongshore distance (HERRINGTON et al., 1997). For the east-
ern Cell 2 between the Leigh and Whilldin Avenue groins
there was a gain in sand volume of 2,761 cu m (3,611 cu yd)
for the period between May 1994 and May 1995. From May
Figure 17. Location of the Beachsaver Reef installation at Cape May
1995 to April 1996, a loss of sand volume was measured at
Point, New Jersey.
650 cu m (850 cu yd). Over the two-year study, there was a
net gain of 2,111 cu m (2,761 cu yd) of sand in the cell, with
the most pronounced accretion on the eastern side of the cell
A gallon volume of Rhodamine dye was released on the
(Figure 19). The most gain was found in the nearshore and
inside of the reef between the Lehigh Avenue and Whilldin
foreshore portion of the profile around 122 m (400 ft) land-
Avenue groins and on the west side of the Coral Avenue groin
ward of the reef.
in the control area to compare the rate of dispersal between
A gain in sand volume in Cell 3 between the Willdin and
the reef area and the non-reef area. Measurements were
Coral Avenue groins was reported as 868 cu m (1,135 cu yd)
made at three times over a tidal cycle. The dye was released
between May 1994 and May 1995. A loss of 488 cu m (638 cu
on a flooding tide and was measured 10 minutes after release,
yd) was measured for the second year between May 1995 and
April 1996 (HERRINGTON et al., 1997). A net gain of over the
approximately 1.5 hours after high tide, and on an ebbing
two-year period was 380 cu m (497 cu yd). Again, the most
tide.
Table 4. Monitoring of Beachsaver Reef at Cape May Point, New Jersey.
Year
Month
Profile Survey
Wave Data
Settlement
Events/Other Monitoring
1994
May
Pre-Survey
June
Beachsaver Installation
September
Post-Survey
Settlement
Dye Study
November
Survey
Settlement
1995
February
Survey
Settlement
May
Survey
Settlement
July
Survey
Wave Gages
Settlement
September
Survey
Settlement
December
Survey
Settlement
1996
April
Survey
Settlement
August
Survey
Settlement
Journal of Coastal Research, Vol. 19, No. 3, 2003
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