How do we measure coastal currents in Vlore?

1. Where is Vlore?

Vlore, an energetic coastal city in the south of Albania, is a spot where history, culture, and natural beauty merge. It fronts the Ionian Sea, one of the inland seas that comprise the larger Mediterranean Sea. That makes Vlore a major port and a hotspot for both citizens and tourists alike.

Geographically, Vlore is set on a gently sloping coastal plain, with the city gradually rising from sea-front. The coastline contains a mix of sandy beaches, rocky cliffs, and small coves. The sandy beaches, such as Patok Beach, are highly popular during the warm summer months among sun seekers and water sport enthusiasts, while the rocky areas provide a unique habitat for a variety of marine organisms.

Vlorë is a city with a very diverse and rich cultural background. Throughout its history, this city has been ruled by different civilizations such as Illyrians, Greeks, Romans, and Ottomans. It contains many historic monuments, among them the Kaninë Castle, which dates back to the 4th century BC. The views of this ancient fortress range from spectacular views of the city down to the sea. The sea plays an important part in the local culture, as the local people gain much from the sea in both fishing and maritime activities.

In relation to its coastal waters, Vlor is bordered by a quite shallow continental shelf that drops off very gradually into deeper waters. The waters are rich in marine life; the fauna includes several fish, octopuses, and sea turtles species. In the Ionian Sea off this area, currents are driven by the larger-scale circulation patterns of the Mediterranean Sea, together with local wind and tidal forces.

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

Actually, the nature of coastal currents near Vlora is an effect of complex interaction. The major factor for such conditions would be the wind. In the region, many kinds of wind prevail. A strong north-western wind blowing during the summer, known as meltemi, drives the surface waters to the coasts, and as a result, onshore currents can take place. Such onshore currents would transport warmer open sea water into the coast with its nutrients for a rich marine fauna.

On the other hand, a cold northeasterly wind called a bora is able to push the water offshore. The boras are infamous for suddenly bringing strong, violent gusts, particularly in winter. The effect of this on currents can eventually modify the temperature and salinity of waters near shore, which in turn influences the distribution of marine life.

Tidal forces also play a role in the coastal current dynamics. Although the tides in the Ionian Sea are relatively small compared to some other regions, they still contribute to the overall movement of the water. The ebb and flow of the tides can interact with the wind-driven currents, either enhancing or counteracting their effects.

Another important factor is the regional bathymetry. The topography of the seabed around Vlore is irregular, with areas of shallows, deep channels, and underwater reefs. These can accelerate, decelerate, or change the direction of currents. For example, a narrow underwater channel will constrict the flow of water, increasing the current speed, while a large reef can deflect the current.

Further contribution to the above-mentioned coastal currents can be brought about by the river runoff, for example from the nearby rivers - Vjosa River. In the case of such rivers discharging freshwater into the sea, this alters the density of the sea water. Because of this density difference, some density-driven currents are created that, together with the already prevailing wind- and tide-driven currents, make the flow patterns more complicated.

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

Surface Drifting Buoy Method

The surface drifting buoy method is the easiest technique to monitor the surface-level coastal currents. Small buoys are fitted with GPS tracking devices and are set into the water. While the buoys are carried by the currents, their movement is tracked in space over time. By analyzing the buoy's trajectory, scientists can estimate both speed and direction of the surface currents. This technique does have some limitations. Surface winds at times considerably affect the movements of the buoys, which then could give the buoy a different path from the actual current. Also, this can give information only on the surface layer of water, and not the deeper-layer currents.

Anchored Ship Method

An anchored ship can be used as a stationary platform for the measurement of current. Current meters are suspended from the ship at several depths. These meters record the velocity and direction of currents at each depth. The procedure makes provision for information on minute details regarding the vertical profile of currents at that location. This method is also restricted to providing detailed information but for a lesser area. It is only representative of the area immediately around the ship, and the presence of the ship itself can potentially disrupt the natural flow of water in that area.

Acoustic Doppler Current Profiler (ADCP) Method

In recent times, the Acoustic Doppler Current Profiler (ADCP) has become a preferred method for measuring coastal currents near Vlore. ADCPs use sound waves to measure the velocity of water at multiple depths simultaneously. They can be deployed from ships, moored to the seabed, or attached to buoys. It is this flexibility that allows the gathering of a greater amount of data. Being less affected by surface-level disturbances like wind, ADCPs yield more accurate true current conditions. They can also provide a three-dimensional view in detail of the current structure in both horizontal and vertical flow components.

4. How do ADCPs using the principle of the Doppler work?

The ADCPs work on the principle of the Doppler effect. When an ADCP profiler sends high-frequency sound waves through water, they come across small particles in the water-plankton, sediment, or even tiny air bubbles. These particles scatter the sound waves back towards the ADCP. This phenomenon causes the scattered sound waves falling on the receiver of the ADCP to change in frequency when compared to emitted waves. Being proportional to this frequency shift-a Doppler shift-is the rule for the magnitude of the velocities of the scatterers, thus the water velocity, relative to the ADCP meter.

Most ADCPs are multiple-transducer-beam instruments. The Doppler shift in each beam is measured and, because an ADCP can generally determine the velocity components of water in three directions, it performs a vector addition to obtain the three-dimensional velocity of the water. This detailed knowledge on the flow of water in all directions is essential for mapping currents inshore accurately.

5. What's needed for high-quality measurement of Vlore coastal currents?

Equipment Material Reliability

In relation to the above, high quality measurements in the coastal waters of Vlore mean that the casing material is among the most critical factors in an ADCP current meter. The casing shall be made of Titanium alloy. For the protection against corrosion by seawater, to which the equipment will continuously be exposed, Titanium alloy has excellent resistance to corrosion. It will have very high resistance against degradation under salty conditions; thus, the ADCP would long-lasting and reliable. Due to its high strength-to-weight ratio, in cases of strong currents or rough seas, the structural integrity of the ADCP would not be threatened either.

Size, Weight, and Power Consumption

ADCP flow meter has to be designed on grounds that it must be small in size and lightweight. Compact design makes it easier to deploy in various settings. For example, it can be more easily installed on a small research vessel or a buoy. A smaller size minimizes the impact on the flow field being measured. Low power consumption is another crucial factor. This allows the ADCP to operate for extended periods without the need for frequent battery replacements or external power sources. This is of especial importance in the context of long-term deployments that Vlore's often-remote coastal areas will require.

Cost-effectiveness

This implies that the ADCP current profiler should be low-cost, which would consequently allow for the large-scale and detailed monitoring of the coastal currents in Vlora. Furthermore, it would also make the ADCPs within the reach of research institutions and environmental monitoring or local initiatives as well. The coverage for the data is greater, all needed for further understanding of these complex dynamics within the coastal current.

6. How to Choose the Right Equipment for Current Measurement?

Depending on the Usage Purpose

• Shipborne ADCP: In this configuration, the ADCP is fitted onto a ship in motion. This is suited best for undertaking extensive surveys regarding the currents nearshore. Essentially, while moving around the coastline, the moving vessel can undertake a continuous mapping of the currents through the ADCP installed onboard to provide the broader-scale observation of the pattern over a much wider area of coverage. That's useful initially during research studies or for assessing variations in these over a vast geographical span.
• Bottom-mounted ADCP: Bottom-mounted ADCPs are fixed on the ocean floor for long-term, fixed-point monitoring. They can be used to determine continuous data from the currents of a particular depth and location continuously. This provides valuable information regarding the local hydrodynamics-for example, the way currents in a particular bay or near some particular underwater topography behave.
• Buoyant ADCP: Buoyant ADCPs, though connected to a floating buoy, are able to drift with the surface currents. They work very well in monitoring the surface and near-surface current patterns. They can also be used in studying the displacement of water masses over time, an important factor in the study of transport of nutrients, pollutants, or marine organisms.

Based on Water Depth

A 600kHz ADCP will suffice quite well for 70m water depth. The higher the frequency of the sound waves, the more the measurements for shallow waters are finer. It has a high-resolution current structure data and hence capable of detecting changes in currents with much smaller scale changes. The depth of the water that corresponds to a 300kHz ADCP is about 110m. This choice offers an appropriate balance in measurement range-resolution. It could reach deeper within the water column than a 600kHz ADCP could but with fairly decent measurements for middle-depth coastal waters.

It is recommended to use a 75kHz ADCP, which can work in deeper waters of up to 1000m. The resolution may be a little lower than that of the higher-frequency ADCPs, but the lower frequency of the sound waves can go deeper. In this case, it would be suitable for the measurement of the currents in deeper parts of the Ionian Sea near Vlore.

There are several well-known ADCP brands in the market, such as Teledyne RDI, Nortek, and Sontek. However, for those seeking a cost-effective yet high-quality option, the China Sonar PandaADCP is a great choice. Made of all-titanium alloy, it offers excellent durability and performance at an affordable price. It is an economic-class ADCP that provides great value for money. You can find more information about it on their official website: (https://china-sonar.com/).

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