Abstract or Summary
Thin-layer placement of sediment (TLP) is an emerging strategy to protect tidal marshes threatened by rising seas. A research team led by the National Estuarine Research Reserve System (NERRS) tested the use of TLP at eight Reserves and developed guidance to inform future research and restoration projects that use this technique. Eight Reserves collaborated to examine TLP as a climate adaptation strategy for at-risk marshes. The team conducted plot-scale studies to evaluate the impact of TLP at different elevations, and tested the use of different sediment thicknesses and compositions. At three Reserves, they also looked at the addition of biochar—plant-based charcoal—to improve soil and plant health.
Findings thus far show that the impacts of TLP vary greatly, with some commonalities. At each site, the sediment addition raised marsh elevation, increased sandiness, and affected soil conditions such as acidity, moisture, and oxygen levels. Vegetation recovered quickly at most sites. Complementary greenhouse experiments conducted by Drexel University revealed that differences in sediment can affect the outcomes of TLP.
Together with scientists and coastal managers from across the United States, the NERRS team developed documents to guide future use of TLP:
Consensus Statement on Thin-Layer Sediment Placement in Tidal Marsh Ecosystems: guidance which explores the potential of TLP to enhance marsh resilience.
- Thin-Layer Placement of Sediment for Tidal Marsh Resilience in the Continental United States: a literature review on the science and practice of TLP to support future research.
- Recommended Monitoring for Thin-Layer Sediment Placement Projects in Tidal Marshes: guidelines for monitoring the success of TLP projects in diverse marshes.
- Guide to Navigating the Permitting Process for Thin-Layer Sediment Placement Projects in Tidal Marshes: a recommended flexible sequence for working through the TLP permitting process.