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
Web Site: http://www.fit.edu
Aerial photograph below is a composite taken 5 July2002. Gran Dominicus is located to the east (right) of the pier, and Iberostar is located west (left) of the pier. Although the beach gained 10 to 13 meters of width due to the installation of the submerged Reef Ball artificial reef in fall 1998, the beaches further to the east and west of the project have remained stable.
Graph below shows the beach profile taken near the center of the photograph above, showing the sand accretion and gain in beach width seaward of the Gran Dominicus Resort following the installation of the submerged Reef Ball artificial reef breakwater.
Increased Beach Width at Center Project - looking west.
February 1999 (left) compared with April 2001 (right) showing large natural sand accretion.