Field Deployment Report: Bottom-Mounted ADCP Profiling in Alicante Port

Deployment Notes: Alicante Port, Spain – October 2023

The salt air hit us the moment we stepped onto the quay, thick with the smell of diesel and Mediterranean brine. We arrived at the Alicante Port docks just as the morning light broke over the Costa Blanca, watching a massive cruise liner navigate the narrow channel. It is a tight squeeze. The port is a chaotic mix of high-volume container traffic and luxury tourism, which makes the water column a nightmare for consistent current readings.

The water state was deceptive. On the surface, it looked like a mirror, but the subsurface dynamics are a different story. We dealt with erratic cross-currents pushed by the wind and the specific geometry of the port's deep-water berths. The Mediterranean doesn't have the massive tidal swings of the Atlantic, but the localized pressure gradients and the constant churn of vessel wakes create a high-energy environment. It is exactly why a standard current meter won't cut it here; you need a full profile to see what is actually happening beneath the surface.

What We Found

The data caught us off guard. We saw significant velocity shears in the mid-column that didn't align with surface observations. In some bins, the water was practically standing still, while just a few meters above, we clocked currents pushing toward the harbor mouth at speeds that would make a tugboat captain nervous. The most surprising bit? The interaction between the deep-water berths and the incoming swell created these strange, rotating eddies. It is a textbook example of how port infrastructure alters natural flow. We spent three hours ground-truthing the data against our handheld sensors, and the ADCP was spot on.

Honestly, the noise levels were higher than I anticipated. With the sheer volume of cargo ships and cruise liners moving through the channel, the acoustic environment is loud. We saw some signal interference (likely propeller cavitation from a nearby ferry) that created spikes in the raw data. However, once we filtered out the outliers, the trend was clear: the current vectors are highly unpredictable near the quay walls. If you are piloting a deep-draft vessel in here, you aren't just fighting the wind; you are fighting a subsurface conveyor belt that shifts every few hours.

Equipment Performance

We deployed a 600kHz ADCP for this run, and it was the right call. The 300kHz unit would have been overkill for these depths and would have given us too much 'dead zone' at the bottom. The 600kHz gave us a clean signal and tight bins, which is critical when you are working in a confined port environment. We had a few scares with biofouling on the transducer faces during the first week, but the data remained stable. The battery life held up well, though the heavy traffic caused some intermittent acoustic shadowing. I've seen worse, but for a high-traffic commercial hub like Alicante, the equipment performed exactly as expected. It handled the turbidity from the dredging operations nearby without dropping the signal.

Recommendations for Future Deployments

If you're heading back into Alicante or a similar Mediterranean port, don't wing it. The interaction between the deep channel and the shallow berths is too volatile for guesswork.

• Use 600kHz or higher to minimize the blanking distance. You need to see the water closest to the seabed to understand the shear.
• Set your sampling interval to 10 minutes. Anything longer misses the wake-induced spikes; anything shorter fills your memory with redundant noise.
• Mount the unit on a heavy-duty tripod with a reinforced base. The bottom currents in the channel can shift the instrument if it isn't weighted properly.
• Perform a sanity check with a handheld current meter during the initial deployment to ensure the ADCP isn't tilted.

The key is the bin configuration. I recommend narrowing the bins to catch those sharp gradients near the berths. Most operators leave them too wide and average out the most interesting data. In a port this active, the 'average' current is a lie. You need the extremes.

Field report by Capt. Marcus Thorne. A veteran oceanographer with 20 years of experience in acoustic instrumentation and maritime hydrography across the Mediterranean and North Sea.