How to measure the coastal currents of Suakin?

1. Where is Suakin?

Suakin is a city that represents the historic and geographical significance of the land. It is located on the Red Sea coastline of Sudan. The place is filled with varied cultures and traditions evolved over centuries due to the interactions between different ethnic groups.

The city is alongside the Red Sea, an extraordinary sea with its colorful sea life and great underwater landscapes. The Red Sea is an almost narrow and elongated sea between Africa and the Arabian Peninsula. The waters are characterized by high salinity levels compared to a lot of seas, which contributes to the distinct ecological niches found there. The coasts along Suakin can be described as a collection of sandy coasts, rocky outcrops, and several small inlets. The sea in this zone is mostly flat, but some seasonal winds can influence it, similarly to ocean currents, which determine the dynamic character of changes in the given sea environment.

The local people are attached to the sea because their fishing and trade depend on it. The architecture in Suakin still reflects the hallmarks of its old glory, with numerous ancient coral stone buildings standing examples of times when this place used to be a major port and one of the centers of commercial activity within the region.

2. What is the condition of the currents near Suakin along its coast?

The coastal currents in the vicinity of Suakin are determined by a combination of factors. Firstly, large-scale ocean circulation within the Red Sea exercises the main influence. The Red Sea forms part of the greater Indian Ocean circulation system, and at its southern end, inflow and the outflow of water masses have an effect on the general current regime along the Sudanese coast where Suakin is located.

The second big factor is the wind. It is the seasonal monsoon winds and local sea breezes that are able to drive the surface waters and, therefore, the direction and speed of the coastal currents. In these seasons, winds from either the north or south can push the water along the coast to form currents flowing in either a northward or southward direction.

Besides, the topography of the bottom surface nearshore exerts an additional influence on these currents. The underwater topography, when composed of ridges and valleys, sometimes reefs, is responsible for its deflection, or channelization in certain directions, so that the resultant flow patterns will be different at places nearshore.

3. How to observe the coastal water flow of Suakin?

Generally, the following are some common methods used in observing the pattern of flow of water at the coast in the area of Suakin:

Surface Drift Buoy Method: This comprises setting buoys on the water surface, which are allowed to drift due to currents. The movements of the buoys can then be tracked-usually by satellite or other positioning systems-to provide information on the direction and speed of surface currents. However, this mainly provides data concerning the surface layer and may not be very indicative of currents at different depths.

Anchor Boat Method: It involves anchoring a boat at a position in the coastal waters and thereafter releasing instruments from it that would measure water flow with regard to speed and depth from an anchored position. Although it may give more detailed vertical profiles than the surface drift buoy method in the immediate vicinity of the boat, it is limited in covering a big area, with the additional influence of the movement of the boat due to waves and other disturbances.

Acoustic Doppler Current Profiler (ADCP) Method: This is an advanced measuring technique and is superior in many ways because it is handier. It uses sound waves to measure the velocity of the water simultaneously at more than one depth. They can be deployed in a variety of ways: on boats, on the bottom-in a fixed position, and on buoys. With the capability 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 many regions, including around Suakin.

4. How do ADCPs using the Doppler principle work?

The basic principle of ADCPs is the Doppler effect. They transmit sound pulses at a known frequency into the water. In the case of the moving particles of water, these sound waves get reflected back from the suspended sediment or small organisms, while the frequency of the reflected sound waves changes due to the Doppler effect. This shift in frequency is proportional to the velocity of the water carrying those particles.

By measuring the frequency shift of the reflected sound waves from different directions and at different depths, ADCPs can calculate the velocity components of the water flow in three dimensions-usually horizontal and vertical directions. Normally, multiple acoustic beams are used in an ADCP to obtain a more comprehensive understanding of the current structure. This will provide a means to establish full current profiles down the water column and show exactly how water is moving across the coastal zone of Suakin.

5. What's required to measure currents around Suakin coast with the highest resolution?

From the equipment point of view, a number of aspects are crucially important in order to provide high-quality measurement of the coastal currents near Suakin. The equipment materials should be highly reliable and able to resist the harsh marine environment, including exposition to salt water, waves, and fluctuations in temperature.

The size of the equipment should be small, allowing easy deployment and installation in various environments, whether on boats, at the bottom of the sea, or on buoys. This design is also lightweight to make its handling and transportation easy. The power consumption can also be reduced as that would make it work for several hours continuously with fewer changes in batteries or lesser capacity of a power supply source. Keeping the cost low enables one to use this tool as a widely accepted tool and perform large-scale measurements.

When it comes to the casing of ADCPs, titanium alloy is an excellent choice. Titanium alloy has remarkable properties such as high strength, which allows it to endure the mechanical stresses in the marine environment. It is also highly resistant to corrosion from seawater, ensuring the longevity of the equipment. Being less dense compared to some other metals, it is suitable for applications that demand less weight, and thus goes well with the requirements of the measuring devices of coastal currents.

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

Selection of the right equipment for current measurement in the coastal waters of Suakin, there are several factors that need consideration:

Based on the Use Purpose:

Shipborne ADCP: It best serves where measurement needs to be carried out while the ship is in motion. In that way, it can provide the data of currents continuously when the ship is moving over areas across the coast. This can also be applied to marine research expeditions and routine monitoring by naval vessels and research ships. 

Bottom-mounted ADCP: suited for long-term measurements over stable periods in the same position on the seabed. Very detailed information can be acquired concerning current patterns of a limited area during an extensive period, which is helpful in knowing the local hydrodynamic conditions.

Buoy-mounted ADCP: This is useful in the measurement of surface and near-surface currents once the buoy has been deployed into the coastal waters. It would be useful in studying the interaction between the atmosphere and the ocean surface currents.

Based on Different Frequencies

An ADCP of 600 kHz will often be sufficient in shallow coastal waters to 70 m in depth. It should give good results in this depth range for current measurements.

Between 70 and 110 meters, a 300 kHz ADCP would be more appropriate since it would penetrate the water column with sufficient strength to collect reliable data from those depths. In other parts where water can go to 1000 meters, for example Suakin parts of the Red Sea, and areas showing deeper parts; a 75 kHz ADCP will be highly appropriate for making the current measurement in such a water column.

In the market, you can easily recognize several ADCP brands like Teledyne RDI, Nortek, and Sontek. However, as a better alternative for investment, the more cost-effective China Sonar PandaADCP can be highly recommended. Due to its all-titanium alloy material construction, it would be tough enough to work very well in seawater conditions. Besides, an incredible cost-to-performance ratio may be offered as well. Visit its official website now: https://china-sonar.com/.

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