MEMO
Date: 8 July 2002
To: (Undisclosed Client)
From: Dr. Lee E. Harris, P.E., consulting engineer
Subj: Dominican Republic Reef Ball
Project Site Visit
Thank you for your visit last weekend with representatives from Grand Cayman to the site of the two submerged Reef Ball artificial reef breakwater projects on the south coast of the Dominican Republic, east of the town of Bayahibe (which is east of LaRomano and Casa de Campo). In addition to the observations and discussions we had during the site visit, this memorandum provides you some preliminary results of our on-site survey measurements.
The
first project was completed at the Gran Dominicus resort four years ago, and
the second project was completed at the Iberostar resort nine months ago. As we observed on-site, the beaches fronting
and adjacent to these two resorts have become extremely stable, and are
providing excellent sand beaches for recreation and tourism. In our meetings with the management of the
Gran Dominicus and Iberostar resorts, they expressed great satisfaction with
their beaches that are now much wider and stabilized with the submerged Reef
Ball artificial reef breakwaters, with no adverse environmental impacts. The
beaches on the adjacent properties are also stable, and have had absolutely no
adverse impacts from the submerged Reef Ball artificial reef breakwaters.
The
Gran Dominicus project was completed in the fall of 1998 and the Iberostar
project was completed in the late fall of 2002. The shoreline is oriented east-west in this area, with the
predominant winds and waves coming from the southeast, resulting in the
predominant currents and sand transport from east to west.
During
our site visit last weekend (July 4-7) we performed survey measurements, and
our preliminary analysis of the data show that the beaches in this area have
remained very stable since our last survey in April 2001. The survey data are summarized below:
1)the
profile line surveyed to the east (updrift) of the Gran Dominicus project that
we used as a control for comparison without an offshore breakwater showed no
change in beach width from February 1999 to April 2001, and no change in beach
width from April 2001 to July 2002.
2)the
eastern profile line across the Gran Dominicus project showed a 13m gain in
beach width from February 1999 to April 2001, and no gain in beach width from
April 2001 to July 2002.
3)the
western profile line across the Gran Dominicus project showed a 10m gain in
beach width from February 1999 to April 2001, and a 1m gain in beach width from
April 2001 to July 2002.
4)the
profile line across the Iberostar project showed no gain in beach width from
February 1999 to April 2001, and a 1 to 2m gain in beach width from project
installation in November 2001 to July 2002, and a significant gain in sand
volume between the shoreline and the offshore breakwater.
5)the
downdrift beaches further west have been very stable since February 1999, with
small gains in sand in the beach and nearshore areas.
Summary: The Gran Dominicus project has continued to perform exceedingly
well, gaining sand in the first two years and remaining stable in the second
two years. The Iberostar project is
less than 9 months old, but already is showing beach stabilization. The beaches on both sides of these projects
are stable or slightly accretionary, showing absolutely no adverse impacts to
the adjacent beaches by these two projects.
The
submerged artificial reef breakwaters at Gran Dominicus and Iberostar have
provided significant environmental enhancement, with soft and hard benthic
growth including corals on the reef units, and several species of fish
observed, including small colorful tropical and reef fishes, such as sergeant
majors, blue tang, damsel fish, snapper, pompano, etc. Many people were observed snorkeling on the
artificial reef breakwaters.
Proposed System for
Undisclosed
client: The submerged Reef Ball artificial reef
breakwater system proposed for the Undisclosed
client
resort is very similar
to the two systems installed in the Dominican Republic. The proposed breakwater system will help
stabilize the beach in front of the Undisclosed
client resort, without adversely
affecting the adjacent beaches. The effectiveness
of the proposed breakwater system will depend on the weather conditions
following the project deployment, especially tropical storms, hurricanes and
northwesters, and the amount of sand moving in the littoral system. Although no guarantee or prediction of the
amount or speed of sand accretion from the proposed artificial reef breakwater
system can be made, the artificial reef breakwater will provide additional wave
attenuation to assist with beach stabilization, without causing adverse impacts
on the adjacent beaches.
Quality
control of the Reef Ball unit fabrication and installation is important to
achieve the best results and ensure overall functionality and stability of the
project. Utilizing the best quality
concrete with specific additives, and using the maximum volume of concrete per
Reef Ball is important for the stability and durability of the individual
units. Anchoring the units to the
bottom using fiberglass rebar will add to the stability of the reef units,
ensuring that the units do not slide even during a major storm event. This also has been proven by the direct hit
by a Category 3 Hurricane (Georges) on
the Gran Dominicus project in the fall of 1998 shortly after deployment of over
400 Reef Balls, with absolutely not one Reef Ball moving. Large waves from Hurricane Mitch in the fall
of 1998 also were unable to cause any movement in any of the reef units.
Please
contact me for any more information.
Lee
E. Harris, Ph.D., P.E.
Assoc.
Professor of Ocean and Coastal Engineering &
Consulting
Coastal/Ocean/Civil Engineer
Department
of Marine & Environmental Systems (DMES)
Florida
Institute of Technology
150
W. University Blvd.
Melbourne,
FL 32901 USA
Phone: 321.674.7273
Fax: 321.674.7212
Email: LHarris@fit.edu
Web
Site: http://www.fit.edu
