How do we measure Durres' coastal currents?

1. Where is Durres?

Durres, otherwise known as Durrës, is a major coastal city in Albania. It lies on the central-western coast of the country, looking towards the Adriatic Sea. Its position has made it one of the most important port cities throughout history, taking part in every kind of trade within the Balkan region and with other Mediterranean states.

Geographically, Durres is set on a relatively flat coastal plain with the Adriatic Sea opening in front of it. The city is a combination of urban development with natural coastal features. The coastline near Durres has a mix of sandy beaches and rocky outcrops. The sandy beaches are tourist attractions during summer, while the rocky ones contribute to the unique ecosystem along the coast.

Durres is a culturally rich and diverse city that has been home to Illyrian, Roman, and Byzantine civilizations since ancient times. It is also home to a number of historical landmarks. Among the many historical landmarks that Durres has, the ancient amphitheater is one, built in the 2nd century AD. It once hosted gladiatorial contests and other public events and now stands as a symbol of the city's long-standing history. The local population is very attached to the sea, where fishing was an important part of the traditional economy.

Regarding its coastal waters, Durres is located on the Adriatic Sea, part of the Mediterranean Sea. Generally, there is an increase in sea depth with increased distance from the shore. The waters around it have different species such as fish, crustaceans, and mollusks. The currents are part of the larger-scale circulation patterns of the Adriatic Sea.

2. What is the state of the coastal currents off Durres?

Several factors affect the coastal currents around Durres. Wind is a primal determinant. Different wind variants act upon the Adriatic Sea. The region is quite familiar with the 'maestral', a north - westerly wind. This in turn may produce, through action on surface waters during summer, an onshore current along the coast. Onshore currents may bring in lots of nutrients from the open sea, thus enriching the biodiversity of the local coastal ecosystem.

Conversely, it may be displaced offshore by a cold northeasterly wind, the bora. Most often, the bora shows up with a greater suddenness and strength, particularly during the winter months. Its action upon the currents results in variations of water temperature and salinity along the coast.

The tidal forces also contribute to the dynamics of the coastal currents. Although the tides in the Adriatic Sea are relatively small compared to some other seas, 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 strengthening or weakening them.

The bathymetry of the region is another important factor. The seabed off Durres is irregular, containing shallows and deeper channels. These underwater features may accelerate, decelerate, or even change the direction of the currents. For example, a narrow underwater channel can constrict the flow of water, increasing the current speed.

The river runoff also can drive coastal currents. In the case where rivers pour fresh water into the sea, this can dilute the sea water and hence decrease its density. This density gradient can create a density-driven current, which can interact with prevailing wind- and tide-driven currents and further complicates the flow patterns.

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

Surface Drifting Buoy Method

The surface drifting buoy method is a rather basic and functional technique of surface level-coastal currents' observation. Small buoys fitted with tracking devices like GPS are disposed in the water. The buoys carried by the currents are monitored from time to time. Based on the path that the buoy traverses, scientists can make an approximate estimation regarding the speed and directions of the surface currents. In fact, this method has further limitations. These buoys can be easily influenced by surface winds, which may deflect them from the actual path of the current. Besides, it gives the records of only the surface layer wind and not for the deeper-layer currents.

Anchored Ship Method

An anchored ship may be used as a stationary platform for the measurement of currents. Current meters are suspended from it at different depths. These meters can record the velocity and direction of the currents at each depth. This approach gives detailed information on the vertical profile of currents in a place but is confined to the small area it can cover. It is only representative of the area in the immediate vicinity of the ship, and the presence of the ship can potentially disrupt the natural flow of the water itself.

Acoustic Doppler Current Profiler (ADCP) Method

The Acoustic Doppler Current Profiler (ADCP) has become a preferred method for measuring coastal currents near Durres. 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. All these possibilities in deployment allow collecting data in ways that would be impossible otherwise. ADCPs do not get interfered with so much by disturbances at the surface, such as wind, tending to offer more accurate real current conditions than other methods can. They may give a quite detailed three-dimensional view of the current structure by including both the horizontal and vertical flow components.

4. How Do ADCPs Using the Doppler Principle Work?

The ADCPs are based on the principle of the Doppler effect. An ADCP meter sends high-frequency sound waves into the water, which collide against the small particles in the water like plankton, sediment, or even very small air bubbles. These particles scatter the sound waves back in the direction of the ADCP. The frequency of the scattered sound waves received by the ADCP profiler differs from that of the waves emitted. It is this differential in frequency-the Doppler shift-which directly relates to the velocity of the particles, and hence the water, relative to the ADCP.

Most ADCPs are multibeam instruments. The Doppler shift measured in each beam allows the ADCP to compute the three components of water velocity in three dimensions. The vector addition of the velocity components will provide the three-dimensional velocity of the water, which allows detailed insight into how the water is moving in every direction, essential for proper mapping of coastal currents.

5. What is called for in regard to high measurement quality of currents in the coast of Durres?

Material Reliability for Equipment

Having high-quality measurements in the water of Durres requires, firstly, the proper material for an ADCP casing. The recommended material for its casing is of titanium alloy. The corrosion of the equipment exposed to seawater will be noticeably reduced because a titanium alloy displays excellent resistance in this regard. It should not degrade over time in the salty environment through long-term immersion, ensuring the ADCP would survive for a long period in reliable condition. Its high strength-to-weight ratio implies that the ADCP would hold its structural integrity in strong currents or rough seas.

Size, Weight, and Power Consumption

The ADCP flow meter is desired to be small in size and light in weight. This would not only save energy but also reduce the price. It would also make installation in a wide range of environments more feasible, whether on a small research vessel or on a buoy. It would also result in less interference with the flow field under measurement. On the other hand, low power consumption is crucial in making ADCP run continuously for longer use without needing frequent battery replacements or an external power source. This is especially important for long - term deployments in the often - remote coastal areas around Durres.

Cost-effectiveness

The ADCP current profiler should be economically viable to enable large-scale and comprehensive monitoring of the coastal currents in Durres. A less expensive ADCP would allow more research institutions, environmental monitoring groups, and local initiatives to purchase the equipment. This, in turn, could lead to more widespread data collection, which is so essential in underpinning a better understanding of the complex dynamics of coastal currents.

6. How to choose the right Equipment for Current measurement?

Depending Upon Purpose of usage

• Shipborne ADCP: This refers to the ADCP current meter mounted on a moving ship. It is very ideal for making large-scale surveys of the coastal currents. While the ship cruises along the coast, the shipborne ADCP can continuously measure the currents with the ability to provide a broad-scale view of the current patterns over a large area. This is useful for preliminary studies or to study changes in the currents over a wide geographical area.
• Bottom-Mounted ADCP: These are seabed-mounted ADCPs used for long-term fixed-point monitoring. They can deliver continuous data about the currents at a certain depth and location continuously. This becomes valuable in understanding the local hydrodynamics, such as how the currents act and behave around a particular bay or near an underwater feature.
• Buoyant ADCP: These can float attached to a buoy, and thus, buoyant ADCPs are free to move with the surface currents. They are well - suited for monitoring the surface and near - surface current patterns. They can also be used to track the movement of water masses over time, which is important for studying the transport of nutrients, pollutants, or marine organisms.

Based on Water Depth

Within 70m of water depths, an ADCP of 600kHz would be quite suitable. The higher the frequency of the sound waves, the more detailed the measurements in shallower waters. High-resolution data regarding current structure, it is very easy to detect small-scale changes in the currents.

• A 300kHz ADCP can suit about 110m water depth. This gives a very good balance between the measurement range and resolution, while it is deeper in the water column than one would obtain with a 600kHz ADCP; it still offers a reasonably good measurement for mid-depth coastal waters.
• In deeper waters up to 1000m, a 75kHz ADCP is recommended. The sound waves have lower frequencies that can penetrate deeper into the water but with somewhat reduced resolution compared to higher-frequency ADCPs. That would make it suitable for deeper parts of Adriatic Sea currents near Durres.

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.