Radar Inlet Observing System (RIOS): Continuous remote sensing of waves, currents, and bathymetry at tidal inlets

Radar Inlet Observing System (RIOS) remotely senses waves, currents, and bathymetry at tidal inlets and river mouths. RIOS utilizes a 25kW X-band, coherent-on-receive radar to measure wave parameters at 3m resolution up to 3km radius from the antenna. Data acquisition and processing are fully automated and capable of hourly observations and web posting from a small, mobile trailer. Wave shoaling and breaking, obtained from the time series of radar spikes generated by the roughened surface of waves, are used to infer water depths and identify the position of shoals and channels. The ability of RIOS to measure wave orbital velocities (radial components) in order to determine mean surface currents is also investigated. Results from a field experiment at New River Inlet, North Carolina in April-May 2012 indicate RIOS accurately characterized the location and morphology of shoals and channels across the ebb tidal delta over a range of quiescent and storm conditions. The magnitude of RIOS-measured surface currents were substantially less than in-situ observations and showed great sensitivity to sea surface roughness.