Issue
The 63rd Street demonstration project site can be described as an "erosional hot spot"
within the federally authorized Dade County Beach Erosion Control and Hurricane
Protection Project (BEC&HP). The authorized BEC&HP is designed to provide a specific
level of storm damage reduction and recreation benefit through the establishment and
maintenance of a beach nourishment design template. This design template must provide
for the life of the project in order for realization of the return on Federal and non-Federal
investments. Monitoring of the BEC&HP indicates that shoreline recession at the
demonstration project site exceeds the rates experienced on adjacent shorelines.
Technology
A design has been selected using Reef BallTM units as an offshore reef breakwater. Reef
BallsTM are hollow concrete hemispheres designed for marine habitat enhancement. Placed
in parallel rows as an offshore breakwater, Reef BallsTM will reduce the wave energy
reaching the beach both by physically blocking the incident waves and by generating
turbulence through the interstices in and around the concrete units. More information on
Reef BallsTM are usually fastened to a hard substrate with fiberglass reinforcing bars.
However, the Miami site has a sandy substrate. To provide stability and prevent the units
from sinking into the sand, the Reef BallsTM will be mounted on concrete articulated
mattresses.
The purpose of the breakwater is to reduce wave energy reaching the beach, thereby
reducing the movement of the sand, extending the time between renourishments, and
increasing the storm protection to adjacent buildings. Additional benefits of the Reef
BallTM design include improved habitat for marine life, and as the Reef BallsTM become
covered with marine growth, the design will provide recreational benefits as a snorkeling
trail.
The primary objective of the demonstration project is to maintain template dimensions
between renourishments in an innovative or nontraditional manner. This demonstration
project will also document the performance of other methods implemented to maintain the
beach nourishment design template at other erosional hot spots in the BEC&HP (e.g., use
of submerged rubble-mound reef for wave attenuation, and use of T-head groins or
headland structures for sediment retention).
Status
Physical model testing of the proposed design has been completed, and a final design has
been determined based on the model tests. The design has been presented to State and
Federal agencies for permitting. A coastal processes evaluation of the project site was
completed in coordination with the Dade County BEC&HP. Innovative and nontraditional
products and/or methodologies for reducing erosion at the project site were solicited.
Points of Contact
Donald L. Ward, CEERD-HC-PS, 3909 Halls Ferry Road, Vicksburg, MS 39180-6199;
phone, (601) 634-2092; e-mail,
Jonas White, CESAJ-PD-P, 400 West Bay Street, Jacksonville, FL 32202-4412; phone,
(904) 232-2481; e-mail,
Program Authorization
Water Resources and Development Act of 1996 (Public Law 104-303, 110 Stat. 3658)
dated October 12, 1996.
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