Coastal sediments include sand, rocks, biological substances, mud and silt, and volcanic lava, among others. These sediments compose beaches and the coastline, and in certain locations they can be found offshore as well. Offshore sediments are typically found in shoals, which are underwater bodies of sediment often associated with previous inlets.
Sediment on beaches is a critical resource because beaches absorb wave energy, thereby protecting natural habitats and man-made structures to their landward side. Beaches also provide space for recreation along the coast. Natural and human-induced erosion threatens this resource and the organisms and activities associated with a healthy beach and dune system.
People can maintain sediment by carefully and sustainably managing the sediment in a given coastal zone. Beaches and dunes can be preserved so that longshore sediment transport is not disrupted. Dredged material from navigation channels can be used to nourish beaches or create wildlife habitats. Underwater shoals can also provide sediment for beach fills.