Submerged Narrow-Crested Breakwaters
705
there is no strong inlet tidal flow influence as was present at
1996a). Minor recovery was measured during the spring of
Avalon and Cape May Point. A truck haul beach fill was also
1995. An active hurricane season in the summer and fall of
placed in this groin compartment along with the Beachsaver
1995 with several storms moving up the east coast offshore
Reef (BRUNO et al., 1996a).
resulted in berm erosion and bar formation in the September
To test the effectiveness of reducing incident wave energy,
and December profile surveys (Figure 22a). The 0 NGVD el-
a 100-unit, 335 m (1,100 ft)-long Beachsaver Reef was con-
evation shoreline moved landward approximately 15.2 m (50
structed between the Pitney Avenue groin in Spring Lake on
ft) over the monitoring period based on profile plots (BRUNO
the south and the 19th St. Groin in Belmar on the north
et al., 1996a; HERRINGTON and BRUNO, 1988). Profile B in
(CRETER et al., 1994). The reef was attached to the two groins
the control area (which did not receive any fill) located in the
about 128 m (420 ft) seaward of MLW, in water depths of 2.3
next groin compartment to the north (downdrift) indicated
to 2.4 m (7.5 to 8 ft) MLW (HERRINGTON and BRUNO, 1998).
that the shoreline remained relatively stable with a seaward
movement of approximately 6.1 m ( 20 ft) over the same
A 6.1 m (20 ft) gap was left to enable a 0.91 m (3 ft) diameter
ocean outfall pipe buried 0.91 m (3 ft) below the bottom to
monitoring period from September 1994 to December 1995
extend offshore, perpendicular to the shoreline. The gap was
(Figure 22b).
filled with a stacked geomattress configuration up to the
crest elevation of the Beachsaver Reef. Reef crest elevations
Sediment Volume Response
of between 0.7 to 1.16 m ( 2.3 to 3.8 ft) MLW were
Measurements of volume within the profile from the berm
measured after placement at this site. The same double thick-
to the Beachsaver Reef indicated that the material placed in
ness geotextile fabric underlayment as was used at Cape May
August 1994 was retained within the profile, but was redis-
Point, was used on this installation for scour protection. The
tributed from the berm to the nearshore bar inside of the reef
polyethylene geomattress filled with stone was placed along
structure (BRUNO et al., 1996a). As of July 1996, the net vol-
both the landward and seaward sides of the base to also mit-
ume change within the groin cell was a loss of 3.3 cu m/m
igate for scour. To further stabilize the reef, steel H-piles
(1.3 cu yd/ft) of sand (HERRINGTON and BRUNO, 1998).
were driven to a maximum depth of 3.05 m (10 ft) below the
bed at all end and transition units (BRUNO et al., 1996a). The
Settlement
ends of the reef were connected to the groins with capstone.
Settlement of around 1 m (3.3 ft) was observed at the Bel-
Monitoring Program
mar site. A 1 m (3.3 ft) layer of medium sand was over a 1
m (3.3 ft) thick clay layer. The settlement stopped once the
The monitoring program at Belmar/Spring Lake was ini-
reef units reached the clay layer (HERRINGTON and BRUNO,
tiated after the Beachsaver Reef was installed. A beach pro-
1998). The settlement ranged from 0.12 m (0.4 ft) at the
file baseline was established along 945 m (3,100 ft) of the
southern end of the reef to around 1.95 m (6.4 ft) at the center
shoreline in September 1994, with 15 beach profile lines. The
of the structure. Most of the settlement was measured in the
survey plan included a north control section with four profiles
first 6 months from September 1994 to March 1995. BRUNO
in the next groin compartment north of the 19th St. groin in
et al. (1996a) concluded that the settlement was related to
Belmar (Figure 21). Six profiles were established in the
the bottom material. Less settlement was measured at the
Beachsaver Reef compartment, with four profiles north and
Belmar/Spring Lake site, possibly because the filter fabric
two south of the ocean outfall location. A south control was
used was thicker than the Avalon installation, as well as ad-
established in the next groin compartment south of Pitney
dition of the rock filled geotextile mattress at the base of the
Avenue groin, with five profile lines (B RUNO et al., 1996a).
reef structure. There was also no open end since the reef was
These profiles were spaced approximately 30.5 to 61 m (100
tied into the groin on either end. More scour was observed in
to 250 ft) apart. Additional surveys were collected in Novem-
areas where the geotexitle mattress was more than 0.6 m (2
ber 1994, and in March, May, September and December 1995
ft) landward of the structure. This distance allowed the sand
(Table 5). Surveys were collected with a total station and
to be undermined and the reef units settled due to the land-
prism rod out to just past the Beachsaver Reef and offshore
ward scour trench.
surveys were collected with a boat mounted fathometer.
Settlement measurements consisted of surveys of the top
of the reef structure. They were collected in September and
Table 5. Monitoring of Beachsaver Reef at Belmar/Spring Lake, New Jer-
November 1994 and March and May 1995 (BRUNO et al.,
sey.
1996a). No wave measurements or dye studies were done at
the Belmar/Spring Lake site.
Profile
Year
Month
Survey
Settlement
Events
Monitoring Results
1994 August
Beachsaver Installation
September
Post-Survey
Settlement
Shoreline Response
November
Survey
Settlement
1995 March
Survey
Settlement
Fill material placed in the Beachsaver Reef compartment
May
Survey
Settlement
on the upper beach by truck was removed from the upper
September
Survey
OctNov
Several Storms
beach during the 1994/95-winter storm season. This sand was
December
Survey
moved to the nearshore landward of the reef (BRUNO et al.,
Journal of Coastal Research, Vol. 19, No. 3, 2003
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