The Tetra Tech team used analytical and numeric modeling to evaluate reef breakwater product alternatives in Louisiana
Photo Courtesy of CPRA’s St. Bernard Parish Living Shoreline Demonstration Project, funded by the Coastal Impact Assistance Program
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The Louisiana coastline loses an average of more than 16 square miles of wetlands per year according to the U.S. Geological Survey. The Coastal Protection and Restoration Authority of Louisiana (CPRA) is the single state entity with authority to develop, articulate, implement, and enforce a comprehensive coastal restoration and protection master plan to reduce hurricane storm surge flood impact, restore Louisiana’s bountiful natural resources, build land to protect critical energy infrastructure, and secure Louisiana’s coast now and for future generations. CPRA selected the Tetra Tech team to design a bio-engineered oyster reef demonstration project to show the potential of using reef breakwater product to combat coastal erosion in St. Bernard Parish. This project was funded through the Coastal Impact Assistance Program (CIAP) and is part of Louisiana’s Comprehensive Master Plan for a Sustainable Coast.
The project is located in St. Bernard Parish’s coastal fringe marsh, which is susceptible to high rates of shoreline erosion due to wind-wave action. The project aimed to establish a living shoreline along 21-miles of coastal fringe marsh to dissipate wave energy before it reaches the shoreline thereby protecting vulnerable shoreline and the valuable marsh behind.
The Tetra Tech team evaluated reef breakwater products to serve as a first line of defense for coastal marshes in the project area, helping to sustain the lower Biloxi Marsh. The project’s secondary goals were to allow sediment accretion between the shore and reef to create new land; stimulate oyster growth and increase the biodiversity in the immediate area; and provide CPRA with valuable data on the performance of various configurations of the selected products that can be used to design more effective projects in the future.
Our team evaluated numerous living shoreline products to determine their potential to meet project goals. Products evaluated included A-jax, gabion mattresses, Reefballs, Reefblk, Hesco basket, and OysterBreak.
The Tetra Tech team performed an environmental analysis of each product, including determining its ability to promote oyster growth, thereby increasing the biodiversity in the immediate area. Our team used analytical and numeric modeling to evaluate the shoreline response and performance of the alternatives using parameters including wave attenuation and sediment transport.
The Tetra Tech team’s services for the living shoreline demonstration included:
Recent and historical data collection (topographic, bathymetric, and geotechnical)
Coastal engineering and modeling analysis
Preliminary engineering and design
Regulatory compliance
Final design
Construction administration support, primarily ensuring all environmental requirements in the permits and specifications were followed
The engineering and design of the project met all three project goals, and our team obtained all necessary permits on schedule to complete project construction during the grant funding period.
Using living shoreline products to protect coastlines in Louisiana provides ecosystem services not available through traditional shoreline protection techniques. The products evaluated as part of this project will provide habitat for fish and other aquatic species, in addition to providing erosion control and shoreline stabilization. Project construction was completed in November 2016, and CPRA is conducting monitoring to evaluate the results of the living shoreline products’ performance.