Deployment Notes: Sharjah Port, UAE - August 2023
The heat hit us like a physical wall the moment we stepped off the quay. It was mid-August in Sharjah, and the humidity was thick enough to chew. We arrived at the berth before dawn to catch the peak of the flood tide, but the air was already stagnant. The water in the basin looked like polished mercury—still, heavy, and deceptively calm. But beneath that surface, the Arabian Gulf was playing its usual games with the port's restricted geometry.
This isn't your typical deep-water harbor. Sharjah Port is a hydrodynamic headache. We were operating in a shallow-water environment where the bathymetry is a mess of erratic slopes and sediment traps. The tide here is micro-tidal, yet the narrow entrance acts like a nozzle. It concentrates the flow, creating these localized jets of water that scream through the channel while the rest of the basin stays sluggish. I've seen this before in the Red Sea. It's a classic bottleneck effect.
Then there is the salinity. The Gulf is one of the saltiest bodies of water on the planet, often pushing past 40 PSU. Combine that with surface temperatures hovering around 35°C, and you get a sharp pycnocline. This density layering bends acoustic signals. If you don't account for the sound speed profile during post-processing, you'll get 'beam steering' and your data will be useless. It's a constant battle to get a clean signal when the water column is essentially a layered cake of salt and heat.
What We Found
The data came back with a shocker: the tidal asymmetry in the basin is far more aggressive than the port authorities realized. We found that the flood currents consistently outpaced the ebb currents. This isn't just a curiosity; it's why the dredging schedules here are such a nightmare. The water pushes sediment in fast and pulls it out slow. We caught several velocity spikes during the flood tide that would make a navigator sweat, all concentrated in the lower water column.
The 'Shamal' winds were starting to kick up during our window. These northwesterly winds scour the Gulf and turn the water into a thick soup of fine silts. The backscatter was off the charts. At first glance, the ADCP reported these massive velocity surges. I almost flagged them as storm surges, but a quick sanity check revealed they were 'ghost currents.' The sensor was locking onto moving sediment plumes rather than the actual water mass. It's a common trap for inexperienced operators who trust the raw data without looking at the correlation values.
We also dealt with the chaos of the port's traffic. Sharjah is a beehive of dhows and container carriers. Every time a bulk carrier lumbered past our mooring, the wake turbulence spiked. I saw velocity jumps that looked like a gale-force event, but it was just a ship passing 50 meters away. We had to aggressively filter out these anthropogenic anomalies to find the actual tidal baseline. Without that filtering, the data is just noise.
Equipment Performance
I opted for a 1200kHz unit for this run, and honestly, it was the only right choice. In these shallow depths, a 300kHz unit has a 'blanking distance' that's far too large; you'd lose the bottom third of your water column to the dead zone. The 1200kHz gave us the vertical resolution we needed to see the shear patterns near the seabed. However, the high sediment load did cause some bin contamination in the lowest cells. The signal correlation dropped significantly near the benthic boundary layer. It wasn't a total failure, but it proves that in turbid waters, you're always compromising between resolution and data reliability.
Recommendations for Future Deployments
If you're dropping gear in Sharjah, don't just 'set it and forget it.' You need a rigorous approach to handle the environmental extremes.
- Use 600kHz or 1200kHz transducers to minimize blanking distance in shallow berths.
- Perform a mandatory sound speed profile (SSP) cast every 12 hours to correct for beam steering caused by high salinity and temperature gradients.
- Set a higher signal correlation threshold during Shamal wind events to eliminate sediment-driven 'ghost currents.'
- Coordinate deployment with port traffic control to timestamp vessel passes, making it easier to scrub wake-induced noise from the final dataset.
- Use heavy-duty mooring weights; the localized jets in the entrance can shift a light tripod in hours.
Field report by Capt. Marcus Thorne. Capt. Thorne is a specialist in maritime acoustics with 20 years of experience deploying hydrographic instrumentation in extreme saline environments.
Field Deployment Report: Bottom-Mounted ADCP Profiling in Sharjah Port