Jekyll Creek Thin Layer Placement Monitoring and Analysis of Ecosystem Response

Description

Thin Layer Placement (TLP) is a sediment placement strategy designed to enhance coastal resilience by supplementing coastal marshes with sediment to help keep pace with relative sea level rise. Coastal wetland loss due to sea level rise and subsidence has impacts on both ecosystem functionality at local scales as well as regionally. Coastal wetlands are nurseries for estuarine, nearshore, and marine organisms. Coastal wetland loss also reduces the extent of natural buffers that protect coastal communities from episodic events such as storms and hurricanes and longer scale erosional events and processes impacting ocean and estuarine shorelines. TLP is a relatively new beneficial use of dredged material technique employed by the US Army Corps of Engineers (USACE) and others to support coastal resilience. The technique is supported by the Regional Sediment Management (RSM) program and successful demonstration projects have been conducted in New Jersey, Maryland, and Louisiana to list a few. While USACE has demonstrated successful construction of the projects, additional research will increase the understanding of the effectiveness of Thin Layer Placement (TLP) as a method to support coastal resilience and beneficial use of dredged material. The data gathered can be used to evaluate the effectiveness of the placement strategy in achieving ecosystem and habitat function goals. Jekyll Creek is a portion of the Atlantic Intracoastal Waterway (AIWW) located west of Jekyll Island and south of Brunswick Harbor in southeast Georgia. The control and placement sites are located in Glynn County, Georgia, on the northeast side of Jekyll Island and are fronted by the Brunswick River and Jekyll Creek. The property is owned and managed by GA DNR. Jekyll Island encompasses 5,700 acres and has more than 1,750 acres of salt- and brackish-water tidal marsh, located primarily on the western part of the island. The control site is approximately 5 acres and the placement site is 5 acres. The dredge material placement was completed in 2018. Program Description/Objective: To evaluate the effectiveness of TLP as a method to support ecosystem and habitat function goals, continued assessments of post project conditions including the placement area and control site are required. The Interdisciplinary team decided not to plant spartina immediately following placement to assess the duration of time for the marsh to recover naturally and based on the current recovery rate it is expected to fully recover in 5 years. The team has monitored the site for three years and requires two additional years of monitoring. Physical and biological monitoring of the treatment and control site once annually for two years using acceptable and established scientific methods is required. The successful applicant will coordinate extensively with the Savannah District and GA DNR throughout the project to ensure successful execution. Objective 1: Conduct field research to assess the following physical parameters: relative marsh elevation/range, tidal range, rate of sea level rise, accretion rates, bulk density, flood analysis, and MSL relative to NAVD88. Elevation and imagery data (surveys, LiDAR, aerial imagery, infrared imagery) will be provided by the Savannah District and Georgia Department of Natural Resources. Objective 2: Conduct field research to assess the following biological parameters: stem density, stem height, percent cover, above ground biomass (end of season peak biomass), below ground biomass (end of season peak biomass), fraction of below ground biomass that is refractory, invertebrates (fiddler crabs, periwinkle snails, other snail species, etc). Objective 3: Prepare reports based on the findings of Objectives 1 and 2 to include documentation of methods, software, and analyses conducted throughout the duration of the assessment. The final reports should also explain factors that influence effectiveness of the placement strategy in achieving ecosystem and habitat function goals and provide recommendations to resource managers regarding best management practices. Reports should be prepared and submitted for each of the monitoring periods performed. The recipient/awardee may be asked to present research findings and monitoring results at public and technical meetings to inform natural resource agencies and the public of the progress of this effort.

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