How do we measure coastal currents at Marsa Alam?

1. Where is Marsa Alam

Marsa Alam is a coastal town that stands on the Red Sea. It is set against an arid backdrop of desert landscape contrasting with the vibrant blueness of the sea waters, Red Sea. The coastline of the town was a haven for beach and marine lovers. It has beautiful sandy beaches running along its shores, while the clear and warm waters of the Red Sea invitingly ask to be explored. In general, the Red Sea here is known for its rich and varied marine life. Among its high points is the presence of very extended and healthy coral reefs. Besides visual excitement, these reefs are of utmost importance because they constitute a home environment for every conceivable variety of fish life, ranging in size from the little, gaudily colorful reef fishes to large, pelagic varieties. Sea turtles, dolphins, and several other kinds of marine mammals are very common visitors that can also be seen frequently by divers off Marsa Alam.

Regarding tourism, this locality has immense potential. This is human geography dealing with activities people do and. Marsa Alam is famous among divers and snorkelers from all over the world for its world-class diving sites and the chance to interact with the varied marine ecosystem. The town has an increasing infrastructure to support tourism: resorts, hotels, and diving centers. Fishing is another traditional activity; local fishermen depend on the generous Red Sea for their livelihood.

The Red Sea, in which Marsa Alam is situated, is a semi-enclosed sea. The characteristics of the water circulation in the area are determined by the larger-scale patterns of the Red Sea, such as the inflow of water from the Indian Ocean through the Bab-el-Mandeb Strait. The local topography, including the shape of the coastline and the presence of underwater features like coral reefs and shoals, also plays a crucial role in shaping the water movement and coastal currents.

2. What is the situation of the coastal currents near Marsa Alam?

The coastal currents around Marsa Alam have a lot of controlling factors. A main determinant would be the large-scale circulation of the Red Sea. The water coming from the Indian Ocean through the Bab-el-Mandeb Strait, combined with thermohaline circulation-in which the driving force is essentially provided by differences in temperature and salinity-sets the general flow that influences the coastal currents.

Wind patterns play a major role. Winds blowing across the Red Sea can create the surface currents. For example, in different seasons, the directions and strengths of winds may be different, leading the surface water to move in a particular direction and then enhance or alter the pre-existent current patterns. The other key factor is seafloor topography around the coast of Marsa Alam. Ridges, canyons, and shoals underwater force the water to bend and alter the flow rate in one direction or another.

It also highly depends on the gravitational pull of the moon and the sun, which results in the tides. The tidal currents in the coastal areas of Marsa Alam may be strong, especially in bays and inlets. The interaction of tidal currents with other factors leads to the creation of a complicated and dynamic pattern of water movement.

3. How to observe the coastal water flow of Marsa Alam?

Surface Drifting Buoy Method

This method involves the deployment of buoys at the water surface that are free to drift with currents. Employing satellite-based tracking systems or any other positioning methods to monitor the buoy movements over time can obtain information about the direction and speed of surface currents. However, this method provides data mainly for the surface layer and may not give a complete picture about the currents at different depths.

Moored Ship Method

In this method, a ship is moored at a certain place in the coastal area and the instruments on board measure the water flow characteristics. This may again result in pretty accurate data just around the ship but has its drawbacks: the presence of the ship may alter the local flow, whereas spatial coverage can be poor beyond the immediate area of the location of the anchored ship.

Acoustic Doppler Current Profiler (ADCP) Method

ADCP has advancedly, better efficiency in the measurement of coastal currents. Acoustic waves depend on velocity measured within various water depths. Emitting an acoustic pulse with the analysis of reflected, Doppler-shifted signals allows the ADCP device to develop a fairly fine profile of the current between the surface and specified depths. This enables a finer view of the vertical structure of coastal currents around Marsa Alam and is less impacted by the influence of exterior factors, such as by the ship itself.

4. How does the principle of Doppler work in ADCPs?

The operation of ADCPs is based on the Doppler principle. They emit acoustic signals into the water. If these acoustic signals intercept any moving particles in water-like sediment, plankton, or other small organisms-frequencies of the reflected signal change. This change is proportional to the velocity with which the particles are moved.

The ADCP has several transducers that transmit and receive acoustic signals in various directions. By determining the Doppler shift in more than one direction, it is able to calculate three-dimensional velocity components of water. These are integrated to find the overall flow velocity and direction of water at different depths.

5. What is required for good quality measurement of the Marsa Alam coastal currents?

The equipment shall contain materials that are reliable enough to conduct high-quality measurement of coastal currents in Marsa Alam. It has to withstand a harsh marine environment that is inclusive of the corrosive effect of seawater and the high pressure at greater depths. The equipment also needs to be as small as possible and of lightweight construction. This makes deployment either from a buoy, a small boat, or a fixed platform that much easier.

Special regard is given to low power consumption, especially during long-term monitoring. It is supposed to be able to operate with restricted power sources, like batteries or solar panels. Another important factor is cost-effectiveness: in order to carry out large-scale measurements along the coast of Marsa Alam, the equipment must be affordable.

For ADCP casing, titanium alloy is a perfect material. The corrosion resistance of the titanium alloy is very high, which is able to bear the corrosive seawater. It also has a high strength-to-weight ratio, allowing for a durable yet lightweight design. This material can better endure the high-pressure environment at greater depths, ensuring the reliability of the equipment during deep-water measurements.

6. How to Select appropriate equipment for current measurement?

Based on the Usage Purpose

• Ship-borne ADCP: This would be quite suitable should the intention be to measure the currents while the ship is in motion or during a particular voyage along the coast of Marsa Alam. It can be installed on the hull of the ship and collect data while the ship sails.
• Bottom - mounted ADCP: For long - term, fixed - location monitoring of the currents near the seabed, a bottom - mounted ADCP is the way to go. It can be firmly mounted on the seafloor for accurate information of water flow from the bottom upwards.
• Buoy-mounted ADCP: When the objective is to measure the currents at different depths in a more flexible way and over an area, then a buoy-mounted ADCP shall be preferred. It can drift to a certain extent with the currents while collecting data during its movement.

By Frequency

• In water depths up to 70m, a 600kHz ADCP would be ideal since it can provide high-resolution measurements suitable for the generally relatively shallow coastal waters around Marsa Alam.
• For water between 70m and 110m deep, the better balance between measurement range and accuracy would be a 300kHz ADCP for medium-depth waters.
• In the case of deeper waters reaching up to 1000m, the 75kHz ADCP should be preferred since it has better depth penetration and thus may yield reliable current data from deeper parts of the coastal area of Marsa Alam.

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.