How to measure the coastal currents of Yanbu?

1. Where is Yanbu?

Yanbu is a city found on the western coast of Saudi Arabia. It faces the Red Sea and is one of the important port cities in the region. The city is famous for its strategic location, being an important hub for trade and commerce.

The landscape of Yanbu harmoniously combines arid desert with the glittering Red Sea. The main part of this seafront area consists of a chain of sandy beaches along the coastline, lashed by the clear blue waters of the sea. In fact, the waters of the Red Sea around Yanbu boast all types of marine life, with colorful coral reefs creating an underwater wonderland. These reefs, besides providing a habitat for several species of fish, also attract divers and marine biologists from all over the world.

As for human activities, Yanbu is a heavily industrialized city. It is one of the leading centers in the land for the petrochemical industry, with refineries and chemical factories set up in every nook and corner. Its fishing is strong, too, as there are ample possibilities within the rich waters of the Red Sea. The sea dominates the local culture: people have a great seafaring history and tradition of trade.

Adjacent waters of Yanbu belong to the greater area of the Red Sea. The Red Sea is a semi-enclosed sea, and the coasts of Yanbu have its specific circulation impact. In some places, the sea is narrow and can provide more concentrated and sometimes stronger currents compared to open ocean conditions.

2. What is the situation of the coastal currents near Yanbu?

Several factors prevail in the coastal currents in Yanbu: the large-scale ocean circulation in the Red Sea being the dominant factor. The Red Sea is influenced by the inflow of water from the Indian Ocean through the Bab el-Mandeb Strait. This, in conjunction with the thermohaline circulation, which is density-driven due to the differences in temperature and salinity, sets up a general pattern of water movement in the Red Sea that affects the coastal currents near Yanbu.

Another critical factor involves wind patterns. The seasonal winds across the Red Sea may drastically influence the surface currents. During the summer, for instance, the winds can push the surface water in one direction thereby changing the pattern of coastal currents.

Another factor would be the seafloor topography around Yanbu's coast. The underwater ridges, canyons, and shoals can also make the water change its direction and speed of flow. The tides, which result from the gravitational pull of the moon and the sun, are also influencing coastal currents. Tidal currents near Yanbu can become quite strong in some places, most especially near narrow inlets and bays.

3. How to Observe the Coastal Water Flow of Yanbu?

Surface Drifting Buoy Method

This involves releasing buoys onto the water surface, which are allowed to drift with currents. The position of these buoys can be tracked over time by satellite-based tracking systems or other positioning methods, and from this, we can estimate the direction and speed of the surface currents. However, this method mainly provides information about the surface layer and does not give a complete picture of the current profile from surface to seabed.

Moored Ship Method

A ship is anchored at a given location in the coastal area. Instruments on the ship measure the characteristics of the water flow in the surroundings. The method can be quite accurate for the area around the ship. It has, however the following disadvantages: the presence of the ship itself disturbs the local flow, while it covers only a limited area.

Acoustic Doppler Current Profiler (ADCP) Method

ADCP current meter is more advanced and efficient in measuring currents along coasts. Acoustic waves are used in ADCP profiler in order to provide the velocity of water at each depth. ADCP measures a profile of current from surface to a limiting depth by emitting acoustic pulses and then analyzing the Doppler shift of signals reflected back. This provides a full understanding of the vertical structure of the coastal currents around Yanbu and is less prone to interference from external factors such as those from the ship itself.

4. How do ADCPs using the principle of the Doppler work?

The ADCPs work on the principle of the Doppler effect. They transmit acoustic signals into the water. If these signals encounter moving particles in the water-sediment, plankton, or small organisms-the frequency of the reflected signals is changed. This change in frequency is proportional to the velocity of the moving particles.

Some general characteristics of ADCP flow meter instruments can be listed as a couple of transducers that operate by emitting and receiving an acoustic signal in various directions, since it can calculate the Doppler shift in multiple directions to find the three components of the water velocity. With this, it integrates in calculating the overall flow water velocity and direction at any depth.

5. What's necessary for high-quality measurement in Yanbu coastal currents?

For the measurement of the coastal currents in Yanbu with high quality, the equipment should be made from reliable materials. It should be able to withstand the harsh marine environment: the corrosive effect of seawater and the high pressure at greater depths. The desirable size and weight of the equipment are small and light, respectively. This will make deployment easy on either a buoy, a small boat, or a fixed platform.

In particular, long-term monitoring requires low power consumption. The equipment should be able to operate on limited power sources, such as batteries or solar panels. Another important factor is cost-effectiveness. It is not practical to carry out large-scale measurements along the coast of Yanbu if the equipment is not affordable.

In the casing of ADCP current profiler, titanium alloy is an ideal material. The corrosion resistance is very high in the case of a titanium alloy; hence, it is absolutely necessary to bear up under the corrosive seawater. It has a high strength-to-weight ratio, which allows for strength without adding much weight. In this way, this material will be able to withstand more of the high-pressure conditions at greater depths and will thus ensure the reliability of the equipment during deep-water measurements.

6. How to Choose the right equipment for current measurement?

According to the Usage Purpose

• Ship-borne ADCP: Where one wants to measure the currents with a ship in motion or even on a voyage along the coast of Yanbu, a ship-borne ADCP is appropriate. This type of ADCP can be fixed in a ship's hull and it collects data while the ship sails.
• Bottom-mounted ADCP: If long-term fixed location monitoring of the currents near the seabed is needed, a bottom-mounted ADCP is in order. It can be firmly placed on the seafloor to provide accurate information about the water flow close to the bottom.
• Buoy-mounted ADCP: If the purpose is to measure currents at variable depths in a more flexible manner and over an area wider than a point, then a buoy-mounted ADCP should be used. It is able to drift to some degree with the currents while collecting data during its movement.

Based on Various Frequencies

• ADCP at 600kHz would be the optimal choice for water up to 70m depth-high resolution but well-matching measurements for shallow waters facing Yanbu coastal.
• ADCP with a 300kHz rating could operate in water from 70 meters to 110 meters of water depth. This balance within medium-depth waters could resolve, with reasonable accuracy, current discharges.
• For deeper waters, up to 1000m, a 75kHz ADCP is recommended. It can penetrate to greater depths and provide reliable current data in the deeper parts of the coastal area around Yanbu.

There are well-known ADCP brands such as Teledyne RDI, Nortek, and Sontek. However, a Chinese brand, China Sonar PandaADCP, is also worth considering. It is made of all-titanium alloy, which provides excellent durability. It also offers an impressive cost-performance ratio. You can find more information on its website: https://china-sonar.com/.

Here is a table with some well known ADCP instrument brands and models.