Deployment Notes: Jeddah Port, Red Sea - October 2023
The heat hit us the moment we stepped off the transport. It was 38°C, but the humidity coming off the Red Sea made it feel like a sauna. We arrived at the Jeddah Port docks just as the morning light started to illuminate the massive container cranes. The water looked deceptively calm, a shimmering turquoise, but the sheer volume of traffic—giant TEU carriers and tankers—creates a chaotic hydrodynamic environment. You can feel the vibration of the port's industry in the air.
Monitoring currents here isn't a standard textbook exercise. The Red Sea is a unique basin with high salinity and extreme temperature gradients that mess with the speed of sound. In Jeddah Port, you have the added complexity of deep-draught channels meeting shallower coastal fringes. The water is dense, salty, and often carries suspended sediments from port operations, which can create a nightmare for acoustic signal processing if you aren't using the right frequency.
What We Found
The velocity profiles were surprising. We saw sudden, sharp spikes in current speed that didn't align with the predicted tidal charts. These weren't tidal surges. They were likely 'wake-induced' flows from the massive ships navigating the narrow channels. The sheer displacement of a loaded VLCC (Very Large Crude Carrier) moving through these waters pushes a wall of water ahead of it, creating localized currents that can easily exceed 1.0 m/s in the lower water column. It's a chaotic mix of natural tidal flow and man-made turbulence.
I noticed significant shear layers. At 10 meters depth, the water was moving steadily seaward, but just a few meters above the seabed, the flow reversed or stalled. This kind of vertical shear is dangerous for smaller vessels and critical for understanding how pollutants or silt settle in the harbor. We spent hours ground-truthing the data against surface floats, and the ADCP caught fluctuations that the floats completely missed. The data was noisy, but the trends were undeniable: the port's geometry is funneling water in ways the original charts didn't predict.
Equipment Performance
We deployed a bottom-mounted ADCP, and for the most part, it held its own. I'll be honest: the 600kHz unit outperformed the higher-frequency options here. Why? Because the Red Sea's high salinity and the port's turbidity can cause signal attenuation. The 600kHz frequency gave us a clean signal with minimal bin contamination, even when the water got murky. We did run into a few 'bad bins' near the seabed—likely due to the rough texture of the port floor—but we trimmed those out during post-processing. The battery life held up well despite the heat, though I always worry about seal integrity in these high-salinity environments.
Recommendations for Future Deployments
If you're heading back to Jeddah or any similar high-traffic Red Sea port, don't just trust the tide tables. You need a denser array of sensors to capture the ship-induced turbulence.
- Use 600kHz or 300kHz transducers to penetrate the turbid, high-salinity water.
- Increase the sampling rate to 15-minute intervals to catch the transient peaks caused by vessel transit.
- Deploy a secondary CTD (Conductivity, Temperature, Depth) sensor to calibrate the speed of sound in real-time; the salinity here is too volatile for a constant value.
- Use heavy-duty mooring weights. The currents in the channels can be erratic and might shift a light tripod.
Field report by Dr. Kenji Sato. Dr. Sato is a specialist in underwater acoustics and oceanographic instrumentation with 20 years of experience in river and marine discharge measurement.
Field Deployment Report: Bottom-Mounted ADCP Profiling in Jeddah Port