The objective of this project is to test a novel modeling approach to quantify how well existing salt marshes buffer flooding, wave energy, and runoff increase coastal resilience to stressors, such as buffer flooding, reduce wave energy, and prevent erosion and runoff caused by natural hazards. A salt marshis a coastal wetland that is flooded and drained by salt water brought in by the tides. The project team will use lessons learned from evaluation of existing sites to develop recommendations for an initial salt marsh design framework based on desired marsh performance. The specific technical objectives are to (1) validate and calibrate the innovative salt marsh design model to be completed for at least one long-established reference/benchmark site and two recent restoration sites, (2) evaluate wave attenuation and habitat performance at the marsh sites under historic conditions, (3) evaluate wave attenuation and habitat performance at the marsh sites under a range of scenarios, and (4) use lessons learned to develop initial recommendations for a framework linking modeling, field and lab research, monitoring, and design evolution. 

The technology is an innovative salt marsh model that integrates hydrodynamics, waves, morphology, and vegetation growth/death. While other salt marsh models exist, none are both spatially distributed and directly couple vegetation biomass growth/death with salt marsh bottom accretion and compaction. The inclusion of these processes will support a better understanding of the relationships between specific marsh characteristics and performance objectives. The purpose of the model will be to (1) evaluate existing salt marsh habitat and wave attenuation performance under current and projected future natural hazards at specific sites and (2) draw initial recommendations for a salt marsh design framework from the site evaluations. Success will be achieved if the model can reasonably reproduce existing marsh behavior, quantify marsh wave attenuation and habitat performance under multiple natural hazard scenarios, and begin to reveal clear relationships between performance metrics and marsh characteristics. This would also ideally result in the development of a draft design framework that links modeling, field and lab research, and monitoring to inform salt marsh design for specific performance objectives. 

Natural hazards particularly around the coastal environment are critical national security issues and threat multipliers that cost billions of dollars in damages and degrading mission capabilities. Hurricane Michael, in November 2018, resulted in $4.9 billion in repairs to rebuild Tyndall Air Force Base and two years of delayed mission. Salt marshes are present across the Florida coastline and can aid in protecting Department of Defense (DoD) infrastructure for natural hazards. Strategizing for the best and most innovative use of salt marshes, would fulfill the DoD’s crucial mission to rebuild military infrastructure and revitalize America’s defense industry rapidly but at a reasonable cost. This model would improve how salt marsh restoration projects are currently designed. Current practice focuses primarily on habitat creation and relies heavily on in-depth field knowledge. The model developed as part of this effort would improve understanding of the relationships between marsh site characteristics and specific performance metrics like percent wave attenuation. This improved understanding would feed into a framework that could provide and quantify the direct benefits to upland structures such as levees by reducing potential erosion. Additionally, this framework could eventually lead to more reliable salt marsh design and construction, resulting in less post construction corrective costs. This framework could also help expand the use of salt marshes as reliable wave attenuation structures where appropriate throughout coastal DoD installations. Since salt marshes provide a large range of benefits from flood reduction to recreation to habitat creation, their return on investment is multi-faceted and long-lived. (Anticipated Project Completion - 2026)