Best Management Practices for Post-Construction Restoration of Rights-of-Way in Saltwater Marshes, Estuaries, and Other Tidally Influenced Areas

2020PDFTech ReportChristian, JasonKim, SonnyDurham, Stephan A.Sutter, LoriHikouei, Iman SalehiHouse, KatelynUniversity of Georgia. College of EngineeringGeorgia. Department of Transportation. Office of Performance-Based Management & ResearchUnited States. Department of Transportation. Federal Highway AdministrationGeorgia. Department of Transportation. Office of Performance-Based Management & ResearchGeorgiaUnited StatesBulk densityCoastal zone managementEstuariesMarshesRestoration ecologySaline soilsSalinitySalt water areasSalt Marsh RestorationSoil Bulk DensityHalophyteFHWA-GA-20-1711PI# 0015709Final Report (November 2017\u2013June 2020)Saltwater marshes or salt marshes are capable of providing to fauna and flora a biologically desirable environment while operating as a sink for sequestering large amounts of heavy metals. Salt marshes have the highest value of net primary productivity among terrestrial and wetland ecosystems and are adversely impacted and threatened by land-use change. Preservation and restoration practices for salt marshes require well-established databases characterizing these coastal areas based on vegetation, soil, and water. This study uses field-based experiments to characterize the native halophytic species and pore-water properties found along the Georgia coast. In addition, laboratory-based experiments were carried out to identify texture, bulk density, carbon to nitrogen (C/N) ratio, trace elements, and the mineralogy of the hydric soils of eight salt marshes located along Georgia\u2019s shoreline. A greenhouse experiment was conducted to evaluate the growth of four predominant salt marsh vegetation types (Spartina alterniflora, Juncus roemerianus, Schoenoplectus tabernaemontani, and Borrichia frutescens) in eight engineered soil mixtures that approximate the physical and chemical properties of salt marsh soils, along with two controls providing baselines for growth in potting soil, as well as growth in the material specified in the current GDOT construction specifications for restoration of disturbed salt marshes. The results demonstrate that growth rates of halophytes depend on salinity of pore-water and soil constituents and properties such as texture, bulk density, organic matter, and mineralogy. Further, resulting statistical analyses reveal a correlation among salt marsh\u2013predominant vegetation types and pore water redox potential. Also, percent organic matter and fine content of salt marsh soils are statistically significant drivers of soil bulk density.104