Sediment bulk density is a physical property of the sediment bed that tells scientists how compacted the particles are. … These analyses are used in beneficial sediment reuse and marsh restoration projects in places like San Francisco Bay, where marshes buffer shorelines from storms but are in danger of drowning due to sea-level rise if sediment accumulation can’t keep up. … To accurately calculate ρdry in a system as complex and dynamic as the San Francisco Bay and Sacramento–San Joaquin Delta, USGS scientists decided to create a site-specific model, described in a newly published study.