Wetland, Stream Bank, and Shoreline Restoration
Product Case Study
Stabilizing Oyster Creek's Outfall
Coastal dune lakes are freshwater lakes located within two miles of an ocean coastline. These rare ecosystems are only found in a handful of locations around the globe, including Madagascar, New Zealand, Australia and South Walton County, FL. Walton County is home to 15 coastal dune lakes, some of which are only a few feet from the Gulf of Mexico. These unique waterways create transitory interchanges between a natural storm water lake and the Gulf. When a coastal dune lake reaches a high water level, it will break through the dune system forming a channel between the lake and the Gulf. The channel, or outfall, is critical for regulating water levels and mitigating flooding
Oyster Lake is one of the coastal dune lakes located in Walton County. Major storms caused Oyster Lake’s outfall to become blocked and urban growth along Highway 30A was causing strain on its overall health. If the outfall remained blocked, it would eventually release thousands of gallons of water, causing flooding to nearby vacation homes.
The County was able to restore the outfall, but it and Walton County residents wanted to reinforce the outfall to protect from future blockages and flooding. In addition to stabilizing the outfall’s channel, another goal of the project was preserving the natural beauty of Oyster Lake. A solution that promotes vegetation was needed, so hard armor reinforcement like rock riprap or concrete block was not an option.
ARMORMAX® Engineered Earth Armoring Solution™ was selected to reinforce the channel sides of the outfall. This system was selected because it provides slope stabilization and erosion control while promoting vegetation. Another important concern for the project was the impact the reinforcement solution would have on the ecosystem, which is home to several endangered species including the Choctawhatchee beach mouse, snowy plover, and loggerhead and green sea turtle.
ARMORMAX is composed of PYRAMAT® High Performance Turf Reinforcement Mats (HPTRMs) and Engineered Earth Anchors that work together to lock soil in place and protect against hydraulic stresses. From cradle to grave, PYRAMAT’s carbon footprint is 2.7 kgCO2 per 1m2 of material. This is about the same impact as driving for six miles. Comparatively, concrete-based alternatives for erosion control are up to 10 times higher, ranging from 20-35 kgCO2 per 1m2.
PYRAMAT is an engineered plastic made from woven polypropylene. The growing concern over plastics and their impact on the environment, specifically the oceans, was a consideration. It’s important to recognize that there are a number of the differences between engineered plastics like PYRAMAT and single-use plastic such as a water bottle. Engineered plastics are stabilized to prevent degradation and designed to perform as long-term or even permanent solutions, whereas single-use plastics are not stabilized, are discarded quickly, and begin to breakdown immediately. Additionally, single-use plastics are made from various unstable polymers that breakdown into microplastics and leach harmful chemicals. PYRAMAT is made from polypropylene, which has been found to contain no leachable components (The Blastic Project 2016-2018).