Semester of Graduation
Master of Science (MS)
Oceanography and Coastal Sciences
Wetlands have many ecological and physical properties that are essential for coastal communities. These ecosystems sustain local economies, provide essential habitats, are a source of numerous ecological and biological services, and protect coastal populations from storms. Of the many wetland types, salt marshes are among the most vulnerable to environmental changes. Salt marshes quickly respond to natural and human-driven perturbations and their high rate of loss in the last century is cause for concern.
In this project the rate of marsh loss driven by channel widening was measured through a comparative analysis of modern high resolution images and historic aerial photography. By comparing the rates of widening among multiple salt marshes, the contribution of different forcings (tidal range, ditching, sediment supply, and relative sea level rise) were evaluated. Tidal range was found to be a poor indicator of widening rates. The impact of ditching, only compared at Barnstable (MA) and Cape May (NJ) was found not to contribute significantly to the rates of widening. The rates of relative sea level rise and changes to sediment supply appear to be the primary contributors to the rates of widening. Channel narrowing was observed at locations with high sediment supply.
Rates of widening within the same salt marsh were also compared. Specifically the rate of widening as a function of channel width – here defined as “widening fingerprints” – was analyzed for channels smaller than 40 m. The hypothesis was that systems dominated by a reduction in sediment supply had different widening fingerprints than systems dominated by relative sea level rise. While fingerprints were clearly detected at Mockhorn Island (VA) and Jamaica Bay (NY), more data is necessary to validate this hypothesis.
Robinson, Jeremiah, "Effects of Natural and Anthropogenic Forcing on Marsh Channel Evolution" (2018). LSU Master's Theses. 4771.