Deployment Notes: Vancouver Port, British Columbia, September 2023
The fog was thick enough to chew on when we hit the docks at dawn. I could barely see the cranes of the container terminals, but the smell of salt and diesel was unmistakable. We were there to drop a bottom-mounted ADCP to get a real handle on the current velocities near the shipping channels. The challenge here isn't just the depth; it's the chaos. You've got massive megaships pushing huge volumes of water, interacting with the complex tidal oscillations of the Georgia Strait. It makes the water column a nightmare of turbulence and shear.
The water was choppy, typical for early autumn in the Pacific Northwest. We dealt with a strong flood tide that pushed against the hull of our deployment vessel, making the precision drop a bit nerve-wracking. The salinity gradients in the port are erratic because of the freshwater runoff from the Fraser River nearby. This creates a stratified mess that can mess with your sound speed profile if you aren't careful.
What We Found
The data came back with a spike that caught us off guard. We saw localized velocity surges that didn't align with the predicted tidal charts. It turns out the geometry of the berths and the sheer scale of the vessels docking creates these weird 'sloshing' effects. We caught a current burst that looked like a rogue wave in the data, but it was actually just a massive carrier displacing water in a narrow channel. It's a reminder that in a working port, the ships are basically part of the hydrology.
I noticed some significant bin contamination in the lower water column. The sediment load in Vancouver Port is high—lots of suspended organic matter and silt. This created a 'noisy' signal in the first few meters above the seabed. We had to scrub the data heavily to separate the actual current flow from the noise created by suspended debris. Honestly, the tidal asymmetry here is fascinating. The ebb tide doesn't just mirror the flood; it's skewed, likely due to the bathymetry of the shelf and the influence of the Strait of Juan de Fuca.
Equipment Performance
We ran a 300kHz unit for this leg. It handled the depth well, but the turbidity was a problem. I've used 600kHz units in shallower harbor settings before, and they usually give a cleaner signal in murky water, but for the deeper channels here, the 300kHz was the only way to get the full profile. The mounting bracket held firm despite the heavy traffic. I was worried about a stray anchor or a piece of debris knocking the sensor off-axis, but the tilt sensor showed we stayed stable within 2 degrees. Still, the signal-to-noise ratio was tighter than I'd like. We spent three hours just doing a sanity check against the surface floats to make sure the ADCP wasn't hallucinating the velocity spikes.
Recommendations for Future Deployments
Next time, I wouldn't trust the standard sound speed constants. The freshwater lens from the Fraser River fluctuates too much.
- Deploy a CTD (Conductivity, Temperature, Depth) sensor alongside the ADCP for real-time sound speed correction.
- Increase the ping rate during peak vessel transit times to capture those short-lived displacement currents.
- Use a heavier concrete anchor base to minimize tilt in high-flow corridors.
- Shift to a higher frequency transducer if the target depth is under 50 meters to cut through the silt.
The Port of Vancouver is a beast of a location. You can't just drop a sensor and walk away. You have to account for the ships, the river, and the weird way the Pacific pushes into the coast. If you ignore the environmental noise, you're just guessing. We got the data we needed, but it took some serious post-processing to get a clean signal. It's a high-stakes environment where a few centimeters of sensor tilt can ruin a month of data.
Field report by Sarah Jenkins. Sarah is a specialist in underwater acoustics and continental shelf currents with twenty years of experience in oceanographic instrumentation.
Field Deployment Report: Bottom-Mounted ADCP Profiling in the Port of Vancouver