concluded that the Beachsaver Reefs stabilized the inshore beach by reducing sand
losses from the beach profile landward of the reef structure. Cell 2 retained almost all of
its sand and cell 3 lost a smaller amount of sand compared with cell 4 that acted as a
control with no structure. Due to limits in the monitoring data, results are somewhat
inconclusive in demonstrating the effectiveness of the structures in retaining sand within
the groin compartments. The Reef units did settle reducing the wave attenuating abilities
of the structure and a scour trough formed on the landward side of the reef units, but the
structure did act as a perched beach retaining sand in the intertidal area of the closed
compartments. Due to continued dune scarping over time, a seawall of rock rubble and
gabions were constructed just seaward of the dune base in cell 5 in 1999 to 2000 to
prevent loss of the dune. A small truck haul beach fill was also placed in cell 3 behind
the Beachsaver Reef and in control cell 4 in 2000 to protect the dune in these two cells
from scarping.
SECTION 227 PROJECT
Beachsaver Reef Installation
As part of the Section 227 project, in the summer of 2002 a new Beachsaver
Reef was constructed at the seaward end of cell 5. The triangular shape Beachsaver
Reef is a narrow-crested prefabricated concrete breakwater structure that is 3.05 m-
long, 4.57 m-wide and 1.83 m-high, weighing 19.1 metric tons (Figure 3). The units
have a narrow crest width of 0.31 m. Individual units were locked together by a built-in
hook and eye configuration to make a long submerged continuous reef structure at the
seaward end of the groins. Rock was placed between the end reef unit and the groin on
each end of the line, enclosing the entire cell as a perched beach, similar to the
configuration of the original deployment in cells 2 and 3. The original objective of these
types of structures is to cause the waves to break as they pass over the crest, but past
experience indicates that they are poor wave attenuators (Stauble and Tabar, in press).
The Section 227 project is to test how well the units retain sand that is trapped within the
compartment by the reef acting as a sill.
Monitoring of the first deployment had showed that the reefs were somewhat
effective in trapping sand within the compartments (primarily in the intertidal area of the
beach profile), but scour at the landward base of the reef caused it to settle and loose
much of its wave attenuation. Wave attenuation was determined to be around 10%.
While most of the sand was retained in cell 2, cell 3 experienced erosion over time
(Herrington et al, 1997). To mitigate for the scour and settlement that was measured in
the first placement, the new Section 227 construction in cell 5 placed units on a geotextile
scour blanket (Figure 4). This linear submerged breakwater structure was tied into the
groins on either end with the placement of rocks to make a completely enclosed perched
beach in that cell, as was done in the first project. The units were placed at a water depth
of 2.7 m so that its crest was even with the water surface at MLW. This placement is
shallower than the original deployments in cells 2 and 3, and the addition of the new
geotextile scour blanket were improvements to this new construction.
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