Field observations of coastal processes (waves, currents, water levels, sediment concentration) in Robe, SA
Field data was collected as part of a PhD project investigating coastal processes around Robe, South Australia.
Waves: Wave heights, periods, and directions were measured using two solar-powered Sofar Spotter wave buoys, which were deployed on 19/12/2022 at a location approximately 8 km offshore of Robe (37°08'27.4"S, 139°39'19.0"E) at a water depth of approximately 30 m, and 1.5 km inshore of Guichen Bay (37°08'53.4"S, 139°46'12.7"E) at a water depth of approximately 10 m. The buoys measured 3D surface displacements at a frequency of 2.5 Hz. Wave spectra and bulk statistics were obtained every 30 minutes.
Water levels: Water levels were measured using a tide gauge (VEGAPLUS 61 by Vega), which was installed in the Robe Marina on 25/10/2022 by the Department of Environment and Water SA. The tide gauge recorded average water levels every 5 minutes based on a 60 second sampling period.
Currents and sediment: An acoustic sediment profiler (Aquatec AQUAscat 1000R) and an acoustic current meter (Nortek Aquadopp 2MHz) were deployed about 1 km north of the Cape Dombey headland (37°08'47.2"S, 139°44'51.3"E) in a water depth of about 12 m for two 8-week periods, one in summer (19/12/2022 - 11/02/2023) and one in winter (20/06/2023 - 21/08/2023). Both devices were attached to a metal mooring frame equipped with sinking weights. The current meter was facing upwards, measuring time-averaged 3D mean currents based on 1 Hz measurements for 20 minutes every hour at a single point 2.1 m above the seaflooor. The 4 transducers of the sediment profiler, which operate at frequencies of 0.5 MHz, 1 MHz, 2 MHz, and 4 MHz, were facing downwards, measuring sediment concentration within 1 cm layers in an 70 cm vertical column above the seafloor at a frequency of 32 Hz for 400 seconds once every 4 hours. The sensors of both devices were facing in opposite directions to avoid interference of the different acoustic signals. The sediment profiler faced downward to capture sediment concentrations near the bed, where they are typically highest due to settling dynamics, while the current meter faced upward to measure current velocities well above the turbulent bottom boundary layer, minimizing disturbance from near-bed turbulence. The current meter has a built-in compass and tilt sensor to ensure accurate orientation and positioning of the instruments attached to a metal mooring frame.
