Matanzas is a natural, unstabilized inlet, which makes it an ideal location to study dynamic inlet processes in a non-maintained channel.
USGS Deploys Oceanographic Gear Offshore from Matanzas Inlet, St. Augustine, Florida
This article is part of the April-May 2018 issue of the Sound Waves newsletter.
Researchers from the USGS Woods Hole Coastal and Marine Science Center conducted a field experiment offshore from Matanzas Inlet near St. Augustine, Florida, as part of the Cross-Shore and Inlets Dynamics project. Matanzas Inlet is a natural, unstabilized inlet, which makes it an ideal location to study dynamic inlet processes in a non-maintained channel. Instrumentation was deployed from January 24 to April 13, 2018, to study seafloor-sediment response to winter storms in the presence of an inlet. The two deployment sites were just offshore from the surf zone in shallow water (site A, approximately 8 meters deep; site B, approximately 15 meters deep) (see map).
An instrumented bottom-lander platform with four legs (a quadpod) and a guard buoy were deployed at each site. The measurements made by the quadpods included tidal- and wave-induced currents, surface waves, water level, salinity, temperature, near-bed turbulence, vertical profiles of suspended-sediment concentrations, seabed elevation changes, and seafloor ripple movement. The buoy at site B was equipped with meteorological sensors measuring wind speed and direction, atmospheric pressure, air temperature, and solar heat fluxes to correlate with the wave, current, and sediment-transport measurements collected by the other sensors. The sites were close enough to shore (1-1.5 kilometers) that the shoreline is visible in the background of the deployment and recovery operations photos.
The Woods Hole team flew to Savannah, Georgia, to work at the Skidaway Institute of Oceanography to assemble the quadpods and meteorological buoy, then loaded them on the R/V Savannah for transit to the deployment site. The ship left port on January 23, 2018, and arrived on site the following day to begin work. The quadpod at site A was the first platform deployed, followed by the nearby guard buoy. The meteorological buoy was deployed next at site B, followed by the adjacent quadpod. The team made CTD (conductivity, temperature, depth) casts at each site, collected sediment samples, and then settled in for the steam back to the dock at Skidaway.
Starting on April 12, the process was reversed, with the Woods Hole team joining the R/V Savannah crew to return to Matanzas Inlet to recover the platforms. The weather cooperated, all the platforms had remained upright where they were deployed, and the work went smoothly. The meteorological buoy and quadpod at site B were recovered first, followed by the guard buoy and quadpod at site A. After the gear was secured, the team made CTD casts, collected sediment samples, and headed back to port the afternoon of April 13, 2018. In the three months of deployment, the platforms became covered with encrusting organisms, but the anti-fouling precautions kept the sensors clean enough to continue making accurate measurements. Once all the platforms were secured on deck, the operational status of each sensor was checked and logged during the transit back to port.
After unloading the ship, the data from each sensor were downloaded. The instruments were cleaned, packed, and prepared for shipment back to Woods Hole. The data return from this program was exceptional: only one instrument failed to collect data for the whole time, and that one did collect data during the first half of the deployment. We look forward to processing the data and using the results to better understand the impacts of storms on the movement of sediment in the presence of an inlet.