Bringing built & natural shorelines together at GTM

Apr 26, 2021 | Guana Tolomato Matanzas, Florida, Healthy Habitats, Reserves, What We Work For

Gabion-break design protects marshes and encourages oyster reefs. Photos courtesy GTM Research Reserve.

Wetlands and other natural places along shore can minimize erosion, anchor habitat, and provide stability even in the face of fierce hurricanes. But in Northeast Florida’s Intracoastal Waterway, they can be overwhelmed by storm driven waves and large boat wakes. Research at Florida’s Guana Tolomato Matanzas (GTM) Reserve is bringing living and built structures together to stabilize the shore and help protect and sustain economically important habitats. 

 At six sites in the Research Reserve, the University of Florida-led team combined two lines of defence—porous wooden breakwalls and oyster catching structures—to reduce erosion at the edge of sensitive marshes and encourage oyster reef development. Known as a gabion-break, this design dissipated damaging, high-energy waves by 30 to 90 percent. The research also helped put boat wakes into perspective.

“One of the most significant results was increased awareness of just how damaging boat traffic can be on natural and built infrastructure,” says Nikki Dix, research coordinator at the GTM Reserve. “If we are going to invest in restoring important habitats like wetlands and oyster reefs, this research shows we need to protect them from boat wake so they can succeed.”

The design, previously used with success in the Netherlands, was tested and improved for application in Florida.  Research reserve staff helped to design the demonstration, build partnerships, support field work, supply technical assistance and data, and assist with written materials, workshops, and public events. The team also created an instructional video and manual to help others follow the process. Together with more than 130 volunteers, they logged more than 640 hours of project support.

“Reserves bring a lot of things needed for this type of research to the table: conservation land, monitoring data, manpower, and outreach,” says Dix. “Through monitoring, we were able to compare oyster reefs on the breakwalls to natural reefs and see how they did—and they did really well! That natural baseline data helps us understand how well oyster restoration works, and how it could be applicable to other habitats like wetlands, and far beyond the bounds of the Reserve itself.”

The GTM pilot has inspired similar installations in nearby estuaries. The design has been replicated at North Peninsula State Park by the Florida Fish and Wildlife Conservation Commission and St. Johns River Water Management District. The commission funded monitoring at both the pilot site and the state park, which allowed comparisons of gabion-break performance in areas of different tidal and boat traffic regimes. In the future, other Reserve teams may test similar breakwalls to protect marshes restored through the thin-layer placement of sediment—an emerging technique to elevate the marsh in the face of sea level rise (SLR).

This project was supported by the National Estuarine Research Reserve System Science Collaborative, a nationally competitive science and knowledge transfer funding program that advances collaborative research to address coastal management problems important to Reserves and their communities. The Science Collaborative is funded by the National Oceanic and Atmospheric Administration and managed by the University of Michigan Water Center.

ReservesGuana Tolomato Matanzas, FloridaBringing built & natural shorelines together at GTM