Date of Award

2024

Degree Type

Thesis

Degree Name

Master of Science in Oceanography

Department

Oceanography

First Advisor

J. P. Walsh

Abstract

Salt marshes provide a wide range of ecological services to the coastal areas they inhabit, but today, salt marshes around the world are increasingly threatened by shoreline development, shoreline erosion, and submergence associated with accelerating sea level rise (SLR). Due to these threats, researchers and coastal managers have become more concerned about the fate of salt marsh systems. This study is focused on the past, present and future of salt marsh units in the upper Narragansett Bay, specifically near Providence, RI. Shoreline and elevation changes were analyzed using available aerial imagery and GPS elevation profiles, as well as accumulation rates in sediment cores measured via 210Pb and 137Cs gamma-spectroscopy. Predicted future extents of salt marshes were evaluated using the collected data, SLAMM outputs, and LiDAR elevations.

Results suggested that the salt marsh study sites experienced site-specific evolution, driven by local factors including shoreline erosion and sedimentation due to natural and anthropogenic influences. SCRs were variable across all sites and appeared to have differing responses due to various types of development and morphological features. Sediment accumulation rates could only be obtained from two steady-state downcore radioisotope profiles, and rates were comparable to the local rate of SLR. The seven other non-steady-state cores likely reflect rapid sedimentation, anthropogenic disturbance, or other processes. Elevation data and SLAMM outputs suggested minimal landward migration is expected at these sites. Considering the collection of data, the form and function of the limited marshes in the Providence River will continue to evolve in morphology and vegetation patterns with some reduction due to shoreline erosion. This research highlights the complexity of small salt marsh systems in developed, dynamic areas.

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