National Erosion Control Development and Demonstration
Program (Section 227)
Sacred Falls Park, Hauula, Hawaii
Description
Sacred Falls Beach Park, Hauula is located at the south end of Makao Beach on the north-
east side of the island of Oahu, Hawaii. The project site is an approximate 113-m (370-ft)
reach of undeveloped shoreline. Seawall-protected private residences bound the small
publicly accessible beach at both ends. The narrow beach becomes inundated at high tide,
and the low-elevation coastal
road that services the area is
poorly protected with ran-
domly placed boulders and
waste concrete piles. In the
nearshore, a wide fringing
coral reef extends along the
coast, with 3.7-m (12-ft)
water depth located approxi-
mately 750 m (2,500 ft)
offshore. The shallow reef
has a mean depth of approxi-
mately 1 m (3-4 ft) at mean
low water (mlw), and is
composed of a mixture of
coral rubble, sand, and
scattered reef blocks over a
Shoreline recession along beach
seabed of hard limestone
substrata.
The Sacred Falls project site is directly exposed to the prevailing trade winds that pre-
dominate from April to September. The large winter north swell refracts and diffracts
around the island and impacts the project site. Coupled with high winter tides, the shore-
line and adjacent coastal highway are occasionally inundated. Tropical storms and hurri-
canes periodically impact the Hawaiian shores. While these storms produce large surf, the
extensive fringing reef at the project site produces a depth-limited breaking wave condition
that expends most of the wave energy before impacting the shoreline. However, numerous
shore protection structures, many of which show signs of deterioration both north and
south of the project site, attest to pervasive yet manageable rates of erosion. The tides are
semidiurnal with a mean tide range of 0.6 m (2 ft).
Issue
Continual, yet manageable, erosion of the beach at Sacred Falls Beach Park has reduced
beach width to a point that it is almost totally submerged during high tide. Some deteriora-
tion of the coast highway is evident. Recreational use of this tourist destination is minimal
due to lack of beach width. Shoreline recession must be abated.
Technology
Project design will include at least one pair of low profile breakwaters/groins to abate
erosion and retain placed fill material, but may also include other structures. The
breakwaters/groins will be designed to allow sufficient sediment to pass over, or around
May 2005
U.S. Army Engineer Research and Development Center
www.erdc.usace.army.mil
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