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Applying dredge sediments to build coastal resiliency in salt marshes
Citation:
Bishop, J., J. Loffredo, D. Perry, C. Chaffee, W. Ferguson, AND C. Wigand. Applying dredge sediments to build coastal resiliency in salt marshes. National Cooperative Soil Survey, Kingston, RI, June 10 - 13, 2019.
Impact/Purpose:
Northeastern states of the US are applying clean dredged sediments to build coastal resiliency in salt marshes. Dredging operations are sometimes carried out to improve nearby navigational channels. Working with state and local partners, the US EPA is examining the effect of dredge sediment placement of 5cm and 10 cm on the marsh surface in a greenhouse experiment. Ongoing state-led restoration efforts using dredge sediment placement in coastal areas in New England will be monitored, and seedling and plant success in both the field and greenhouse experiment will help inform future adaptation efforts to build coastal resiliency.
Description:
Coastal marshes in the Northeast US are vulnerable to increased flooding due to accelerated sea level rise and an increase in the frequency and severity of storms. Some southern New England salt marshes are drowning in place, and observations of increased interior ponding, stunted and dying grasses, and rapid shoreline erosion have been reported. Increasing salt marsh surface elevation by applying dredge sediments is one approach to build coastal resiliency. US EPA is partnering with the RI Coastal Resource Management Council, Save the Bay, and other partners to examine the effects of varying depths of clean dredge material (+ 5 cm, + 10 cm) on sediment biogeochemistry, porewater nutrient chemistry, seed germination, and plant productivity in a greenhouse experiment. This experiment is coupled with field monitoring at a nearby coastal site, Quonochontaug Pond, RI that is currently undergoing marsh nourishment with placement of coastal lagoon dredge sediments on its surface. The dredge materials in the field restoration effort and greenhouse experiment are the same. Preliminary results of seed germination success, pH, redox, salinity and DO of the experimental treatments and controls will be presented. The coupled greenhouse-field research and cooperation among state, NGO, and federal partners allows for innovative adaptive approaches, which address difficult management questions arising from coastal resiliency challenges.