SEDIMENTATION PROCESSES ON A SOUTHERN NEW JERSEY SALT MARSH ISLAND

Global salt marsh degradation and retreat, due to anthropogenic sea-level rise, has become a major global issue for coastal communities. Essential salt-marsh ecosystem services, such as coastal protection, pollutant filtering, nursery habitat, and carbon storage, are at risk of being permanently lost. This project is working alongside the Seven Mile Island Innovation Lab (SMIIL), a partnership that aims to advance dredging and marsh restoration techniques through research collaboration and real-world application. We study sediment transport processes on Gull Island, a back-barrier marsh located in Cape May county, New Jersey. Our main goal is to better understand suspended-sediment transport within a tidal channel. In October 2021, we collected: 7 water samples; 30 conductivity, temperature, and depth-water column profiles; and 13 sediment grab samples from the bed. In addition, we collected two one-meter-long sediment cores on the marsh near the channel. Variations in grain size of bed sediment along the creek will be compared to a recent placement of dredged material at the mouth of the creek. The makeup of channel sediment is a mix of sand, clay, silt, and organic matter. Past and present sediment-accumulation rates will be determined from ¹³⁷Cs dating on sediment cores, and related to current rates of sea-level rise. This project will help the SMIIL partners develop a better understanding of the effectiveness of strategically placed dredged sediment from navigation channels onto marsh islands and at the mouths of tidal creeks as a means to increase accretion rates. If proved effective this could be a strategy used to combat the threat of rising sea-level on coastal salt marshes.