Grain-Size Analysis Data From Sediment Samples in Support of Oceanographic and Water-Quality Measurements in the Nearshore Zone of Matanzas Inlet, Florida, 2018

The interactions of waves and currents near an inlet influence sediment and alter sea-floor bedforms, especially during winter storms. As part of the Cross-Shore and Inlets Processes project to improve our understanding of cross-shore processes that control sediment budgets, the U.S. Geological Survey deployed instrumented platforms at two sites near Matanzas Inlet between January 24 and April 13, 2018. Matanzas Inlet is a natural, unmaintained inlet on the Florida Atlantic coast that is well suited for study of inlet and cross-shore processes. The study sites were offshore of the surf zone in a line perpendicular to the coast in water depth from 9 to 15 meters. An instrumented sea-floor platform was deployed at each site to measure ocean currents, wave motions, acoustic and optical backscatter, temperature, salinity, and pressure with an emphasis on quantifying the forcing for sediment transport and response near the seabed. Sonars mounted on the platform at the shallow site recorded how the sea-floor bedforms responded to forcing conditions. A surface buoy was deployed at each site; the larger buoy at the deeper site supported meteorological measurement of local atmospheric conditions during the study, and both buoys measured near-surface water temperature and salinity. Sediment samples were collected at the study sites to support these oceanographic and water-quality measurements, and grain size was analyzed for use in sediment transport models to compare predicted estimates of sediment resuspension and transport with observed estimates. Grain-size results are presented in phi and μM units.