How are we going to measure the coastal currents of Kilif?

1. Where is Kilif?

Kilif is a coastal area found within a region endowed with a rich coastal environment. It lies along the eastern coast of Africa, with a beautiful bay that serves as a key geographical feature. The surrounding land is a blend of sandy beaches and areas with coastal vegetation, such as mangroves in some parts.

The sea has always been part of the lives of the local communities in Kilif. Fishing is the major source of livelihood along these coasts, and it is for this reason that the bay becomes an important resource area for the locals. The bay around Kilif is host to various types of marine organisms. It hosts a wide variety of fish species, from the small reef-dwelling fishes to the large pelagic fishes that are migratory within the area. The seabed off the Maltese Islands includes sandy areas, coral reefs, and in some places, seagrass beds. Such seabed features act not only as habitat but also impact the flow of coastal currents.

The waters around Kilif are part of the larger Indian Ocean system. There are far-reaching ocean currents that bring in different water masses of varying temperature, salinity, and other characteristics. The tides also play an important role in the coastal environment. The regular ebb and flow of the tides determine the exposure of the shoreline, influence the movement of marine organisms, and affect the distribution of sediment.

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

The coastal currents around the Kilif come from many natural oscillations combined, therefore creating a current pattern that is complicated. One of the predominant forces acting along this coast, which determines the periodic back-and-forth movement of water, is the tides. The tidal range contributes to the magnitude and direction of the tidal current. During high tide, in some cases, the water may rush in with more power, while during low tide, the water recedes to change the flow paths.

Wind is another very important factor: the prevailing winds in the area can push on the surface waters, producing surface currents interacting with the underlining layers of water. Examples include the onshore winds that push the water onto the coast and may result in coastal erosion or deposition of sediment. It is the immediate topography of coastline and seabed that plays an immense role in this. The shape of the bay around Kilif can channel or even defocus the currents, as a matter of fact. The presence of coral reefs and seagrass beds disrupts the smooth flow, thus producing areas of turbulence and eddies.

There is also the interaction between the actual coastal currents and the oceanic currents of the open sea. These greater ocean currents can join the local coastal currents, bringing in new water masses with different characteristics of temperature, salinity, and nutrient content. This can have an impact on the productivity of the coastal waters and the distribution of marine life.

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

Surface Drifting Buoy Method

This technique consists of deploying buoys onto the water surface, which may drift freely with the currents. The buoy's position determination as a function of time, by means of satellite or other positioning systems, enables the determination of the direction and speed of superficial currents. However, this method applies mainly to the surface layer and may fail to provide adequate information on the entire water column.

Moored Ship Method

In such methods, a ship is anchored in some particular place in the coastal area. With the help of instruments on it, the flow of water around it is measured. This can give very detailed information in the vicinity of the ship, but the presence of the ship disrupts the natural flow to a certain extent, and it covers only a small area round about its mooring.

Acoustic Doppler Current Profiler Method

ADCP flow meter is a more advanced and convenient method of measurement of the coastal currents. It uses acoustic waves for measuring simultaneously the velocity of water at different depths. Thus, it can give a very detailed profile of the current right from the surface to a certain depth and gives full understanding of the flow structure of the coastal water. It covers the largest vertical range and in many cases is less affected by external interferences as compared to the other methods; thus, it is considered highly effective for observing coastal currents near Kilif.

4. How do ADCPs using the Doppler principle work?

Basically, ADCPs work according to the Doppler principle. They emit acoustic pulses into the water. These sound waves, interacting with moving particles in the water-suspended sediment or small organisms-change the frequency of the reflected waves through the Doppler effect. The ADCP current meter is designed to detect and measure this frequency shift. With several transducers oriented in different directions, it can determine the velocity components of the water in various directions, such as horizontal and vertical directions. These then enable the three-dimensional flow field of the coastal currents to be reconstructed. The ADCP current profiler continuously sends out these acoustic pulses and records reflected signals at regular time intervals; hence, it is able to build up a time series of the current velocity at different depths, providing a full profile of temporal variations within the currents and with depth.

5. What is needed for good measurement of the coastal currents of Kilif?

Concerning the equipment for high-quality measurement of coastal currents near Kilif, a number of aspects will be important: First, the material reliability of the equipment; it should withstand harsh marine conditions: corrosion by seawater, impact of waves, and changes of temperature and pressure. Small size is an advantage in respect of handling and deployment of the equipment on boats, buoys, and other platforms.

Another very important factor is the light weight that makes the installation easier and less load. Power consumption must be low especially in long-time measurement or with a battery-powered arrangement. The cost has to be also considered to make the measuring point more viable and permit wider and large-scale measurement. To this end, the casing of the ADCP profiler shall be preferably made from Titanium alloy. The advantages of the titanium alloy are outstanding. It has excellent resistance to corrosion; therefore, for a long time, it is able to stand the salinity of sea water without complete deterioration. It is also tough and durable enough to bear up the mechanical load from the current and other tides and impacts. Furthermore, its relative low density ensures that the equipment does not turn out to be overly heavy while maintaining its structural soundness.

6. How to Select appropriate equipment for current measurement?

Based on Usage

• Shipboard ADCP: this is ideal when measurements are required while a ship is in motion or stationary in the coastal area. It can deliver continuous data while the ship moves across various locations along the coast, mapping out the pattern of currents over an extended area.
• Bottom-mounted ADCP: Suitable for fixed-point measurements at the seabed. It can monitor the currents passing over it with high accuracy, therefore providing information on the near-bottom current conditions, which are important in understanding sediment transport and other benthic processes.
• Buoy-mounted ADCP: Mounted on buoys floating on the water surface, it can measure the currents from the surface downwards. It is useful for observing the surface and upper layer current variations and is often used in areas where long-term monitoring without the presence of a ship is required.

Based on Frequency

• A 600 kHz ADCP is quite often a good choice for water depths within 70 meters. The higher frequency allows for better resolution in shallower waters, providing detailed current information close to the surface and down to the relevant depth range.
• For water depths of up to 110 meters, a more appropriate one would be a 300 kHz ADCP. This will adequately penetrate the water column and measure currents at various levels within this depth.
• For very deep waters, say up to 1000 meters, a 75 kHz ADCP will be recommended. Its low frequency allows it to reach that depth and still yield reliable current velocity information.

There are several famous brands of ADCPs on the market, like Teledyne RDI, Nortek, and Sontek. However, those who want a high-quality but inexpensive one should look into the China Sonar PandaADCP. It is made entirely of titanium alloy material, thus ensuring very good durability and performance in the marine environment. With its incredible cost-performance ratio, it offers a great choice for measuring the coastal currents of Kilif. You can learn more about it on its official website: https://china-sonar.com/.

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