Effects of Urban Coastal Armoring on Salt Marsh Sediment Supplies and Resilience to Climate Change

Salt marshes are grassy wetlands that form along sheltered coastlines. These areas provide crucial habitats for many species of birds and other animals, in addition to recreational activities and economic opportunities. Marshes also protect the coast from storms and filter runoff from the landscape, ensuring cleaner and healthier coastal waters. As climate change causes sea levels to rise salt marshes are at risk of being drowned out if they are unable to grow quickly enough to stay above the rising tides. In order to build elevation and endure sea level rise, marshes trap sediment from tidal waters, which accumulates over time to build a platform that marsh grass can grow on. 

Along exposed coasts, humans have built seawalls and other structures to protect homes and infrastructure from erosion. It is believed that reduced erosion as a result of this “coastal armoring” has made it harder for salt marshes to thrive along urbanizing, armored shorelines, as they no longer receive sediment from eroding coasts. This project will use satellite imagery to observe how sediment in coastal waters along the Northeast U.S. varies in response to coastal armoring. A network of sediment samples and cores from marshes with and without armoring will then be analyzed to see if urban marshes receive less sediment following armoring. The data can then provide scientists and coastal decision makers with information on how to help marshes survive sea level rise. If coastal armoring and reduced sediment supply is found to be a contributor of salt marsh deterioration, effective solutions to restore the lost sediment may then be determined. The results of this work will be available to coastal decision makers through partners at NOAA and the USGS.