Discharge measurements made in Bayou Heron and Bayou Middle, Grand Bay, Mississippi in January 2017

Grand Bay, a 30-square-kilometer embayment of the Gulf of Mexico bordered by 20 square kilometers of salt marsh, is experiencing rapid lateral shoreline erosion at up to 5 meters per year. Determining whether the eroded sediment is exported to the deep ocean or imported via tidal channels and deposited on the marsh platform is critical to understanding the long-term response of the marsh to wave attack and sea-level rise. Quantifying water-column sediment flux helps to characterize the role of tidal channels in this process, and water discharge is a key component of sediment flux. To that end, discharge was measured repeatedly over consecutive diurnal tidal cycles in the tidal channels of Bayou Heron and Bayou Middle, within Grand Bay National Wildlife Refuge, Mississippi on January 24-28, 2017. These data were collected by using a Teledyne RDI Rio Grande 1200-kilohertz acoustic Doppler current profiler (ADCP). Downward-looking ADCP transect data were collected from a moving boat and initially reviewed by using WinRiver II, and reprocessing and final review was completed by using QRev.