Engineered Solutions: FLOOD MITIGATION with Green-Friendly Armoring
Esplanade Club Lake is a large resort-lifestyle community development in Fort Myers, Fla. Situated on 778 acres, the community features a number of aquatic amenities, including a large lake, ponds, boat ramp and recreational dock. To support the community’s drainage infrastructure and mitigate flooding, three spillways were built within the development.
Each spillway needed armoring to protect and stabilize its channel and sides. Rock riprap and concrete were both considered, but their harsh look did not match the aesthetic of the Tuscan-inspired architecture. Additionally, these options did not provide environmental benefits in the form of today’s green infrastructure standards. ARMORMAX® Engineered Earth Armoring Solution™ was selected because the system provides resilient flood protection and erosion control while promoting vegetation. Nearly 9,000 square yards of ARMORMAX were installed along the three spillways.
The ARMORMAX system is composed of High Performance Turf Reinforcement Mat (HPTRM) and Engineered Earth Anchors that work together to lock soil in place and protect against hydraulic stresses for up to 75 years. It has been tested and approved by the U.S. Army Corps of Engineers, and has been used to armor more than 100 miles of levees in the New Orleans area.
The system features a patented trilobal design that locks seeds and soil in place to promote rapid root development for long-term vegetation. This vegetated outcome supports a living shoreline, whereas hard armoring can decrease streamside vegetation and adversely impact fish populations. A vegetated shoreline helps to maintain cooler water temperatures than traditional hard armoring, which is healthier for aquatic ecosystems.
Once the ARMORMAX was installed, sod was placed on top for immediate surface erosion protection. The system’s patented X3® fiber technology helps hold roots in place so they are not washed away during rain events. The vegetation establishment of the armoring solution is critical to long-term performance, providing a matrix of woven HPTRM trilobal fibers, roots, stems, and soil to serve as a securing mechanism to the spillway channel and sides.
To help retain the soil and ensure proper drainage, GEOTEX® Nonwoven 401 was installed under the ARMORMAX. GEOTEX 401’s structure easily allows significant amounts of water or air to pass through the fabric while restricting soil particles. To further provide flood mitigation, nearly 20,000 square yards of LANDLOK® 450 was installed on the surrounding lake bank. LANDLOK 450 is a Turf Reinforcement Mat (TRM) engineered to stabilize low-flow areas. Similar to ARMORMAX, it is designed to promote vegetation.
In addition to promoting vegetation, ARMORMAX is more environmentally friendly than alternative armoring methods. From cradle to grave, the carbon footprint of its HPTRM component is 2.7 kgCO2e per 1m2 of material. Comparatively, the carbon footprint of concrete-based alternatives are up to 10 times higher, and rock riprap is up to 30 times higher.
ARMORMAX is an engineered plastic made from woven polypropylene. The growing concern over plastics and their impact on the environment, specifically waterways, was a consideration for this project. There are distinct differences between engineered plastics like ARMORMAX 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 can leach harmful chemicals. ARMORMAX is made from polypropylene, which has been found to contain no leachable components (The Blastic Project, 2016-2018).
Of equal importance, the environmental benefits of ARMORMAX extend into the product’s useful life. Once installed, ARMORMAX helps to decrease sedimentation and pollutants, and encourages infiltration of water back into the groundwater table. These are two reasons why the EPA has identified systems that utilize HPTRMs like ARMORMAX as a Best Management Practice (BMP) for improving water quality.