How do we measure the coastal currents of Umluj?

1. Where is Umluj?

Umluj is an interesting coastal city in northwestern Saudi Arabia along the Red Sea. It is located amidst an area where the arid desert meets the sparkling waters of the sea, therefore, making it a contrasting sight to see.

This is because of its coast of immaculate sandy beaches that stretch over kilometers of shores, lapped gently by the clear, warm waters of the Red Sea. Offshore waters are also within the greater Red Sea area, which is one of the most renowned for the most stunning biodiversity in the marine environment. The Red Sea waters are rich here with colored coral reefs forming intricate undersea architectures and serving as habitat to an unnumbered species of fish, crustaceans, and many other water organisms.

On the human side, Umluj is a city of vast cultural heritage combined with the sea. Traditionally, the people have been engaged in fishing, whereby fishermen depend on the waters for a living. It has also lately started to attract more tourists, mostly due to its unspoiled natural beauty and the opportunity for diving and snorkeling in various water activities.

The gulfs and bays around Umluj have their particular hydrographic features. Local water circulation is linked to the wider Red Sea general circulation patterns but takes its form from local topography, referring to coastline geometry, small islands, and general bathymetry with its shoals and mild slopes.

2. What is the situation of the coastal currents in surroundings of Umluj?

Certain factors determine the characteristics of the coastal currents at Umluj. The large-scale oceanic circulation in the Red Sea constitutes a major factor, given that the latter is linked to the inflow of water from the Indian Ocean through the Bab el-Mandeb Strait. The inflowing water brings its own particular temperature and salinity properties into the Red Sea, driving the thermohaline circulation therein while influencing coastal currents around Umluj.

The wind patterns are also of great significance. Seasonal winds across the Red Sea may displace the surface water in one direction or another. During certain months, for example, the northerly or southerly winds may push the surface layer of water along the coast and either strengthen or alter the existing current patterns.

Another important factor near the coast of Umluj is the topography of the seafloor. Ridges, canyons, and other underwater features in the path of the flowing water may serve to divert its flow. Beyond the tidal forcing that is directly imparted on the water because of gravitational forces by both the moon and the sun, tidal currents will form. In Umluj, tidal currents that may form around bays and inlets could become substantial and combine to make an extremely complicated regime of current.

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

Surface Drifting Buoy Method

Buoy is such a methodology which concerns the placement of buoys on the water surface, which have been left free to drift due to currents. By employing their movements after some time, using the satellite tracking systems or some other positioning technology we understand the direction and speed in which the surface currents of water move. It does, however gives substantially large datasets corresponding only to the surface layer, and provides little idea regarding the horizontal currents at deeper levels.

Moored Ship Method

In this approach, a ship is anchored at a certain place in the coastal area. Instruments on the ship are used to measure the water flow characteristics around it. Though it may afford reasonable data with fair accuracy in the surrounding areas of the ship, yet it has a limitation; it may disturb the local flow by the very presence of the ship, and its spatial coverage is confined to the area around which the ship is anchored.

Acoustic Doppler Current Profiler (ADCP) Method

Acoustic Doppler Current Profiler (ADCP) is more advanced and efficient in the measurement of coastal currents. Acoustic waves in water measure the velocity of the water at various levels. It produces a detailed profile of the current from the surface to the bottom by emitting pulses and analyzing the reflected signals which have been Doppler shifted. This allows for better and more complete insight into the vertical structure of coastal currents around Umluj with less disturbance from outside sources, compared to some other approaches.

4. How do ADCPs based on the principle of the Doppler work?

ADCPs depend on the principle of the Doppler effect. They emit acoustic signals into the water. When these signals come into contact with moving particles in the water, such as suspended sediment, plankton, or small organisms, the frequency of the reflected signals changes due to the Doppler effect. This change in frequency is proportional to the velocity of the moving particles.

The ADCP current meter is fitted with several transducers operating in different directions to transmit and receive acoustic signals. Because the Doppler shift is measured in multiple directions, the ADCP flow meter will be able to calculate three-dimensional space velocity components. These are then integrated to arrive at the overall water flow velocity and direction at each depth in the measurement range.

5. What is required for quality measurement of Umluj coastal currents?

Equipment to be used in measuring the currents of Umluj's coasts must have the following features for high-quality measurement. There is material reliability, where equipment should be able to bear the harsh marine environment, both in the corrosive nature of sea water and at greater depth, high pressure. Another desiderata is small size and low weight, since the latter makes the equipment easily deployed either on a buoy or a small boat or at some fixed location on the sea floor.

The power consumption of the equipment also has to be low, taking into account its long-term functioning. Its operation must have a minimum power source - from accumulators or from solar panels - so data collection may be uninterrupted for as long as possible. The apparatus should be so affordable to make wide measuring in all Umluj coastal areas possible.

The best material choice for the ADCP current profiler casing would also be titanium alloy. An alloy that provides very high corrosion resistance, important in a corrosive seawater environment, it has great strength-to-weight ratio characteristics. These will assure durability yet allow lightweight design properties to endure high-pressure conditions sometimes experienced in deeper waters. In this way, reliability in equipment is ensured through the measurements at different levels of water.

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

According to the Usage Purpose

• Shipborne ADCP: In case one intends to measure currents while the ship is in movement or during particular voyages along the coast of Umluj, the shipborne ADCP may serve better. It can be installed on the hull of the ship and will continuously collect data while the ship is navigating.
• Bottom-mounted ADCP: Bottom-mounted ADCPs are for fixed locations where long-term current monitoring is needed near the seabed. It can be firmly fixed on the seafloor for precise information of the flow of water close to the bottom, which is necessary to understand the interaction between the seabed and currents.
• Buoy-mounted ADCP: This is preferred when the purpose is to measure currents at different depths in a more flexible manner and wider area. It can drift with the currents to some amount while collecting data.

Based on Various Frequencies

• ADCP of 600 kHz frequency can be recommended for depths within 70 meters. This will yield good resolution and give quite accurate measurements for the generally relatively shallow coastal waters around Umluj.
• ADCP with a 300 kHz frequency is suitable for water over 70 to 110 meters in depth. It provides the right balance between measurement range and accuracy for medium-depth waters.
• For waters as deep as 1000 meters, the choice would fall to a 75 kHz ADCP; it can give better depth penetration to obtain current data with higher reliability in the deeper areas of the coastal waters off Umluj.

There are several famous brands of ADCPs on the market, including Teledyne RDI, Nortek, and Sontek. However, a Chinese brand stands out: China Sonar PandaADCP. It is made of all-titanium alloy material, ensuring excellent durability in the marine environment. Besides, it offers an incredible cost-performance ratio. For more information, you can visit its website: https://china-sonar.com/.

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