Does Grain Size Matter? - A Survey of Natural and Restored Marsh Soil Characteristics

Coastal marshes are a natural defense that develop on a variety of geomorphic landforms and occur across a wide range of tidal regimes.Marshes evolve over time in response to changing sea level, sediment supply, vegetation community succession, anthropogenic perturbations, and other factors.These ecosystems provide an important natural defense for coastal communities because marshes reduce wave energy which lowers flood risk and increases resilience.However, many marshes display degradation associated with erosion, decreased sediment availability, and storm damage.In response, coastal resource managers seek to restore and expand marshes to improve environmental outcomes while delivering other benefits to coastal communities.In particular, the beneficial use (BU) of dredged sediments provides a source of materials for marsh creation and restoration, while supporting the maintenance of economically essential navigation channels.The U.S. Army Corps of Engineers (USACE) recently introduced an initiative to increase dredged sediment BU from the current rate of 30-40% of the total dredged volume to >70% by 2030, further promoting marsh creation and restoration.Using dredged sediment that would otherwise be removed from the coastal zone protects critical infrastructure, military installations, and other assets from natural threats (e.g., storm surge and flooding).Yet questions persist regarding what types of BU sediments are appropriate for marsh creation and restoration.In response, we review marsh soil characteristics based on a survey of existing literature.While this review is not exhaustive, our findings show no statistically significant difference between BU and natural marsh soil grain sizes, organic matter, and bulk density, and a large range of values across all marshes.These results promote the application of both fine and coarse textured dredged sediment to create and restore marshes.Our findings also suggest the need to match dredged sediments