Tidal marsh restoration and creation has been proposed as a tool to build coastal resilience in the face of rising sea level and increasing intensity of coastal storms. However, it is unclear what conditions within constructed settings will lead to the successful establishment of tidal marsh. We used sediment cores and historical geospatial data in the tidal freshwater Hudson River to identify the rapid creation and development of marshes that are sheltered by human-made structures including railroad berms, jetties, and dredge spoil islands. These backwater areas rapidly accumulated clastic material following anthropogenic modification that allowed for transition from tidal mudflat to emergent marsh. In one case, historical aerial photos document this transition occurring in less than 18 years, offering a timeframe for marsh development. Accretion rates for anthropogenic tidal marshes and mudflats average 0.8-1.1 cm yr-1 and 0.6-0.7 cm yr-1 respectively, equivalent to 2-3 times the rate of relative sea level rise as well as the observed accretion rate at a 6000+ year old reference marsh in the study area. Paired historical and geospatial analysis revealed that more than half of all the tidal wetlands on the Hudson are anthropogenic and developed since the industrial era, including two thirds of the emergent cattail marsh. These inadvertently constructed tidal wetlands currently trap roughly 6% of the Hudson River’s sediment load. Results indicate that when sediment is readily available freshwater tidal wetlands can develop relatively rapidly in sheltered estuarine settings, and serve as useful examples to help guide future tidal marsh creation and restoration efforts.
About this article
This article has been submitted for publication to Earth Surface Processes and Landforms in 2020. It describes findings from the Dams and Sediment in the Hudson (DaSH) project related to tidal wetland growth in the Hudson River estuary as a result of human activities. It presents sediment accumulation rates in marshes along the Hudson and reveals the rapid growth of marshes associated with anthropogenic structures. This preprint is available at EarthAirXiv Preprints.
Yellen, Brian, Jonathon Woodruff, David Ralston, Caroline Ladlow, Sarah Fernald, and Waverly Lau. 2020. “Rapid Tidal Marsh Development in Anthropogenic Backwaters.” EarthArXiv. March 21. doi:10.31223/osf.io/ga5pm.