How can we measure the coastal currents of Tokar?

1. Where is Tokar?

Tokar is a place of importance, lying on the Red Sea coast of Sudan. This coastline is a mixture of natural beauty and historical beauty. The place has an arid landscape juxtaposed with the endless blue waters of the Red Sea.

On its border lies the Red Sea, famous for its warm and crystal waters, full of very diverse marine life. The general features of the seashores around Tokar include a sandy beach along the rocky formations of this visually and ecologically interesting area. The Red Sea is itself a semi-enclosed sea connected with the Indian Ocean via the narrow Strait of Bab el-Mandeb.

On the human side, local communities have traditionally been connected with the sea through fishing as a primary means of subsistence. The cultural heritage of the area reflects the different ethnic groups that have inhabited the region over time, with traditional practices and stories passed down through generations. It also bears a great deal of historical significance with all those commercial and naval activities of the past, which still partially continue to beautify it.

2. What is the condition of the coastal currents off Tokar?

Several influential factors shape the coastal currents near Tokar. The large-scale oceanographic patterns of the Red Sea play a major influence. Since it is connected with the Indian Ocean, the inflow and outflow of water masses from the broader ocean circulation impact the local current systems. Tides are another factor, as the regular rise and fall of the sea level cause variations in flow patterns along the coasts.

The other important factor is the wind of the region. The seasonal winds, in particular the monsoons, are capable of driving the surface waters and changing the course and speed of the coastal currents. During particular seasons, for instance, the winds blowing from certain directions can easily push the water along the coast and give the currents certain directions. Another factor that modifies these currents is the topography of the seabed off the coast of Tokar. Ridges, canyons, and shoals are common underwater topographic features that may cause the water to be deflected or funneled, resulting in changes in the nearshore flow paths.

3. How to Observe Coastal Water Flow of Tokar?

A number of general methods are used to observe the coastal water flow around Tokar:

The buoy method involves buoys let into the surface of the water, which, when drifting with currents, may then be tracked. Normally through satellite or other positioning technologies, the movements of such buoys can be followed in order to achieve valuable information regarding the direction and speed of surface currents. The method, though, gives only the picture of the surface layer and does not probably provide an overall view of the currents at different levels of depth.

Anchor Boat Method: It is based on anchoring a boat in some selected part of the coastal waters and deploying instruments from the same boat to record flow of water at its vicinity and at different depths. While it may seem to provide more detailed data than the surface drift buoy method, at least for the immediate surroundings of the boat, this method has its own drawbacks in terms of vast area coverage; also, the movement of the boat itself, due to waves and other disturbances, can affect the result.

Acoustic Doppler Current Profiler (ADCP) Method: ADCP is an advanced, very modern, and easy measurement method. It depends on the measurement of water velocity at several depths simultaneously, by means of the principle of sound waves. It can be installed on boats, fixed to the seabed, or on buoys. Thanks to its ability to provide detailed and continuous data on the current profiles from the surface down to significant depths, it has become a preferred choice for coastal current measurements in the Tokar area.

4. How do ADCPs using the Doppler principle work?

ADCPs work on the principle of the Doppler effect. They send out sound pulses at a known frequency into the water. As these sound waves encounter moving particles in the water, such as suspended sediment or small organisms, the frequency of the reflected sound waves shifts because of the Doppler effect. The magnitude of this shift in frequency is proportional to the velocity of the water carrying those particles.

Measuring the frequency shift of the reflected sound waves from various directions and at varied depths, the ADCPs compute the multidirectional-velocity components of the water flow, usually both in the horizontal and vertical directions. Typically, multiple acoustic beams are used within one ADCP for a full understanding of current structure. For this reason, detailed current profiles can be drawn showing just exactly how the water moves at numerous depths along the coast of Tokar.

5. What is needed to achieve high-quality measurement of the Tokar coastal currents?

During high-quality measurements of the coastal currents near Tokar, several main requirements for the equipment come into play. First of all, the materials used in the equipment should be highly reliable to withstand the harsh marine environment: resistant to saltwater corrosion, mechanical impacts due to waves, and temperature fluctuations.

The equipment design should be compact in size for easy deployment and installation in different environments, whether on boats, on the seabed, or on buoys. The equipment should also be lightweight in design to make handling and transportation easier. Low power consumption is preferred to keep the equipment running for longer periods of time without changing batteries frequently or requiring a large power supply source. Cost-effectiveness is another important aspect, as it allows higher diffusion and great measurements on a wide scale.

Outstandingly, the casing of ADCPs is made from titanium alloy. Titanium alloy has several advantages. It has high strength and is able to bear the mechanical stresses in the marine environment. It is highly resistant to corrosion from seawater, thus greatly extending the life of the equipment. Besides some metals, its comparatively low density presents an advantage where there are definite considerations on weight to be used with equipment near the coast of Tokar.

6. How to select suitable equipment for flow measurement?

This selection should have due consideration among others of the following aspects critical to current flow measurement in waters at Tokar

Based on the intended Purpose

• Shipborne ADCP: This is suitable when measurements are required while the ship is in motion. It can provide continuous data on the currents as the ship navigates along the coast. For example, during scientific research voyages or routine monitoring by naval or research vessels.
• Bottom-mounted ADCP: Appropriate for long-term and stable measurements at a fixed location on the seabed, it can give detailed information about the current patterns in a specific area over an extended period, useful for understanding the local hydrodynamic conditions.
• Buoy-mounted ADCP: It is ideal for the measurement of surface and near-surface currents whenever the buoy is deployed in the coastal waters. It can help study the interaction between the atmosphere and the ocean surface currents.

Based on Different Frequencies

• A frequency of 600 kHz can usually be applied in waters up to 70 meters in depth and is hence considered ideal for relatively shallow coastal waters. Proper current measurements could be given out by an ADCP at this depth.
• For the range of 70 to 110 meters, a 300 kHz ADCP would be more appropriate because it effectively penetrates the water column for the measurement of reliable data within the range.
• In areas where the water depth is as deep as 1000 meters, such as in some of the deeper parts of the Red Sea near Tokar, a 75 kHz ADCP would be most appropriate for measuring currents throughout the water column.

Well, in the market, several well-known brands exist: Teledyne RDI, Nortek, and Sontek, among others. However, for those in need of a good quality yet economic option, it is worth mentioning the China Sonar PandaADCP. Material of all-titanium alloy can guarantee its durability and excellent performance in the marine environment. Furthermore, it can offer an impressive cost-performance ratio. You can learn more from its official website: https://china-sonar.com/.

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