Deployment Log: Los Cristianos, Tenerife - October 2023
I stepped off the tender and onto the quay at Los Cristianos just as the morning haze was lifting off the Atlantic. The air was thick with the smell of diesel and salt. This isn't your typical deep-water harbor. It is a high-traffic hub where ferry lines to La Gomera and El Hierro fight for space with whale-watching catamarans and local fishing boats. The water here is deceptively calm on the surface, but the underwater topography is a nightmare for any hydrographer. The rapid transition from the coastal shelf to the deep volcanic drops of the Canary Islands creates erratic local currents that can push a vessel off course during a tight berthing maneuver.
The weather held steady at 24°C, but the sea state was choppy. We faced a particular challenge with the sediment load near the harbor mouth. The constant churning from ferry propellers kicks up fine volcanic sands, which can easily lead to bin contamination in the lower water column. We had to be surgical about where we dropped the sensor to avoid getting a signal drowned out by noise from the seabed interface.
What We Found
The data came back with a spike that caught us off guard. We recorded localized velocity surges nearing 0.7 m/s during the peak tidal shift, far higher than the regional averages for the south of Tenerife. It turns out the harbor's geometry acts like a funnel. The current doesn't just flow; it accelerates as it hits the breakwater structures. This creates a shear zone that any captain bringing a large ferry into the port feels in their steering, though they might not have had the hard numbers to explain why.
We also noticed a strange vertical profile. The surface currents were moving aggressively toward the northeast, while the water just five meters down was almost stagnant or drifting slightly opposite. This vertical shear is common in these volcanic basins but dangerous for stability. I spent an hour ground-truthing the data against a handheld flow meter, and the ADCP was spot on. The noise levels were higher than I liked near the bottom, likely due to the sandy substrate reflecting the pings, but the mid-water bins provided a clean signal.
Equipment Performance
We ran a 600kHz ADCP for this stint. Honestly, it was the right call. A lower frequency would have given us more depth, but we didn't need it here, and the 600kHz offered the spatial resolution required to see those tight velocity gradients. The unit handled the turbulence well, though I noticed some signal dropout during the height of the tourist rush when the harbor was packed with idling engines. The acoustic noise from the vessel traffic is a real factor in Los Cristianos. If you're deploying here, you can't just set it and forget it; you have to filter the data aggressively to strip out the 'ghost' currents caused by propeller wash.
Recommendations for Future Deployments
If you're heading back to Tenerife for similar work, don't rely on the general tidal charts for the Canary Islands. They are too broad for a port this complex. I suggest the following:
- Use a heavy-duty tripod mount with a wide footprint to prevent the unit from tilting in the sandy bottom.
- Set your blanking distance to at least 1 meter to avoid the seabed noise floor.
- Deploy during the shoulder season (May or September) to avoid the extreme acoustic noise generated by the peak summer ferry traffic.
- Coordinate with the port authority to ensure the ADCP isn't placed in a direct dredging lane.
The overall takeaway is that Los Cristianos is a high-energy environment disguised as a tourist port. The currents are fickle. Without a bottom-mounted ADCP, you're essentially guessing based on surface drift, which is a recipe for disaster in tight quarters.
Field report by Capt. Marcus Thorne. Capt. Thorne is a specialist in maritime acoustics and hydrography with twenty years of experience deploying sonar instrumentation in complex port environments.
Field Deployment Report: Bottom-Mounted ADCP Profiling at Los Cristianos Port, Tenerife