Deployment Notes: Tees Port, North East England, October 2023
The wind was biting as we stepped off the quay at Tees Port, that sharp, salty chill typical of the North Sea in October. I remember watching the grey water of the River Tees churning against the harbor walls, thick with suspended sediment and smelling of industrial brine. We were there to get a baseline of the current velocities, but the environment is a nightmare for acoustics. Between the massive bulk carriers churning up the channel and the constant influx of freshwater from the river meeting the tide, the water column is a chaotic mess of salinity gradients and turbidity.
The site is a logistical knot. You have deep-water berths for tankers right next to shallow silt banks. The tide here doesn't just rise and fall; it pushes a wedge of saltwater inland, creating a stratified layer that can trick a poorly configured sensor. Visibility was nearly zero—the kind of 'pea soup' water that makes you rely entirely on your instruments because you can't see your own boots if you drop them over the side.
What We Found
The data hit us immediately: the velocity shears near the bed were far more aggressive than the port's historical charts suggested. We saw peak ebb currents that nearly doubled our predictions in the narrowest sections of the channel. It was a wake-up call. The interaction between the outgoing river flow and the receding tide creates these localized 'jets' of high-velocity water. Honestly, if the port management isn't tracking these in real-time, they're gambling with vessel maneuverability during tight docking windows.
We also noticed significant bin contamination in the lower 2 meters of the water column. The sediment load in the Tees is heavy—lots of fine silts and organic matter. This created a 'noisy' signal near the seabed, making it hard to distinguish between actual water movement and the drift of suspended particles. I had to manually scrub the data to remove these outliers. It's a classic problem in estuarine environments, but it underscores why you can't just 'set it and forget it' with an ADCP in a working port.
Equipment Performance
We deployed a 600kHz ADCP, and it was the right call. I’ve used 300kHz units in similar depths, but the 600kHz gave us the vertical resolution we needed to see those salinity-driven shear layers. The instrument held its position well on the seabed, though we spent an hour fighting with the tripod leveling because the silt was so soft the legs kept sinking. The battery life held up, but the signal-to-noise ratio dipped during the peak flood tide when the turbidity spiked. Still, the Doppler shifts were clean enough for a reliable sanity check against our surface floats. It did the job, but the environment pushed the hardware to its limit.
Recommendations for Future Deployments
If we go back to the Tees, we need to change the strategy. The sediment is too aggressive for standard mounting.
- Switch to a heavier, wide-base gravity frame to prevent sinking into the silt.
- Increase the ping rate during spring tides to capture the rapid velocity shifts in the upper water column.
- Deploy a secondary CTD sensor alongside the ADCP to correlate velocity spikes with salinity changes.
- Avoid deployment during heavy rainfall events; the freshwater runoff increases turbidity and kills the acoustic signal.
The biggest takeaway? Don't trust the charts in an estuary this active. Ground-truthing is the only way to ensure the safety of those tankers entering the channel. The Tees is a living, moving system, and the acoustics prove it.
Field report by Elena Rodriguez. Elena is a specialist in underwater acoustics and oceanographic instrumentation with twenty years of experience in coastal sediment transport.
Field Deployment Report: Bottom-Mounted ADCP Velocity Profiling at Tees Port