How to measure the coastal currents of Canakkale?

1. Where is Canakkale?

Çanakkale is a city in northwestern Turkey, located by the Dardanelles Strait, which connects the Aegean Sea with the Sea of Marmara. This privileged geography has given it important maritime and historical relevance for many centuries. The city lies at the southern coast of the Dardanelles, its unique geographical position allowing for a blend of natural beauty and historical importance.

Geographically, the Canakkale area is an amalgamation of rolling hills, rich plains, and a rugged coastline. The Dardanelles Strait, narrow in places, gives a dynamic marine environment. The bottom topography is irregular, consisting of various features such as underwater trenches, ridges, and sandbars. These physical aspects add to the unique coastal landscape and influence the local marine ecosystem.

Culturally, Canakkale is a city with a rich and varied heritage. It has been a site of great events in history, most notably the Gallipoli Campaign during World War I. Historical landmarks, museums, and memorials all over the city give homage to its past. The local population is highly related to the sea, where fishing and shipping have been traditionally major economic activities. Around Canakkale, there are extensive species of marine life, ranging from different kinds of fish to crustaceans and seabirds.

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

The characteristics of currents along the shores of Canakkale are very complex. The exchange of water between the Aegean Sea and the Sea of Marmara through the Dardanelles Strait forms a very complicated current system. The great difference in the level and salinity of the two seas generates a strong, two-way flow. Surface waters usually flow from the Aegean towards the Sea of Marmara, while deeper waters flow in the opposite direction.

Wind patterns also play a significant role. The prevailing winds in the region can either reinforce or oppose the natural current flow. Northerly winds can strengthen the surface - level inflow from the Aegean, while southerly winds can have the opposite effect. Tidal forces, although relatively small in this area, still contribute to the overall current dynamics. Tidal ebb and flow can combine with the wind- and density-driven currents and thus give variability in speed and direction of coastal currents.

Bathymetry of the Dardanelles Strait is the other important point. The channels are narrow and have underwater topography, such that the velocity of the current increases or slows down, even changing direction in some places. For example, the water can flow more rapidly at the narrowest parts of the strait while being deflected around sandbars or ridges. The river runoff from nearby rivers, even as not as overwhelming compared to many other regions of the world, may still input freshwater into the coastal zone, which might modify the density and flow of seawater.

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

Surface Drifting Buoy Method

The surface drifting buoy technique is a rather simple means for an initial assessment of the coastal currents at the surface level. Small buoys are fitted with GPS tracking devices and are released into the water. Carried by currents, over some time, their movement is followed. From this, the path of the buoy allows the estimation of speed and direction of surface currents. However, this has limitations. The buoys easily get swayed by the surface winds away from the path of the actual current. Besides, this can give information regarding only the surface layer and not the deeper-layer currents.

Anchored Ship Method

The anchored ship acts as a stationary platform for carrying out the measurement of currents. Current meters are suspended from it at different depths. These meters can record the velocity and direction of currents at all depths. It is also through this method that detailed data for the vertical profile of the currents at one site can be recorded while at the same time highly localized. It is representative only of the area in the immediate vicinity of the ship, and the presence of the ship itself can interfere with the natural flow of the water.

Acoustic Doppler Current Profiler (ADCP) Method

The Acoustic Doppler Current Profiler (ADCP) has become one of the preferred methods for measuring coastal currents near Canakkale. 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. This flexibility enables a more comprehensive data collection. ADCPs are less affected by surface-level disturbances such as wind and, therefore, are more accurate in measuring the true current conditions. They can provide a detailed three-dimensional view of the current structure, including both horizontal and vertical flow components.

4. How do ADCPs, working on the principle of the Doppler effect, work?

An ADCP profiler basically works on the principle of the Doppler effect. First, when an ADCP sends high-frequency sound waves into the water, these particles in the water-plankton, sediment, or small air bubbles-bump into these sound waves. Then the scattered sound waves start to head backward in the direction of the ADCP. The scattered sound waves that reach the ADCP have a different frequency compared with the emitted waves. This frequency shift-the so-called Doppler shift-is directly related to the velocity of the particles, and hence the water, relative to the ADCP.

Most ADCPs have several transducer beams, from which the Doppler shift in each beam may be measured and the ADCP meter can work out the velocity component of the water in various directions. With vector addition of these velocity components, the three-dimensional velocity of the water may be determined. This enables one to have a fairly good appraisal of how water is moving along all axes-a necessity for adequate mapping of currents off coasts.

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

Equipment Material Reliability

The material of casing in the ADCP flow meter to be deployed in the coastal waters of Canakkale would be very significant for high-quality measurements. For this reason, the casing being made from a titanium alloy would be an excellent choice. Such a type of metal alloy is much required with its outstanding corrosion resistance because it would face always corrosive sea water. It will not degrade much during long-term immersion in such a salty environment, thus maintaining the longevity and stability of the ADCP. Besides, with a high strength-to-weight ratio, the ADCP will not lose its structural integrity in strong currents or rough seas.

Size, Weight, and Power Consumption

The ADCP current profiler shall be designed to be small in size and light in weight. Compact design for ADCP enhances the ease of its deployment in more varied environments: from installing it on small research vessels to buoy installations. Moreover, this helps in minimizing impact on the flow field that has to be measured. Another related essential consideration regards the ADCP power consumption, the possibility to run with low power means operating for extended periods without reinstallation of batteries or other power supplies. This is especially important for long - term deployments in the often - remote coastal areas around Canakkale.

Cost-effectiveness

The ADCP current meter should be moderately priced to make possible large-scale and comprehensive monitoring of the coastal currents in Canakkale. A lower-priced ADCP will make it feasible for more research institutions, environmental monitoring groups, and local initiatives to afford the equipment. This can then provide a wider-scale data collection, which is really necessary for a better understanding of the complex coastal current dynamics.

6. How to Choose Right Equipment for Current Measurement?

Based on Usage Purpose

• Shipborne ADCP: This is the ADCP that is mounted on a moving ship. It does better for large-scale surveys of the coastal currents. With the movement of the ship along the coast, the shipborne ADCP can continuously measure the currents; therefore, it offers a wide outlook on how the patterns of the current would relate to each other over a big area. Useful for preliminary research or to study how the currents change in a wide geographical area.
• Bottom-Mounted ADCP : Bottom-mounted ADCPs are placed on the seabed for long-term, fixed-point monitoring. It can continuously deliver data on the currents at the same depth and location. Valuable in understanding the local hydrodynamics of how the currents will behave in that part of the Dardanelles Strait.
• Buoyant ADCP: When attached to a floating buoy, buoyant ADCPs are free to move with the surface currents. They have good suitability for monitoring the current patterns at surface and nearsurface. They could also be applied in studying water mass movement regarding nutrient transport, pollutants, or marine organisms through time.

Based on Water Depth

• For water within 70m, a 600kHz ADCP is rather appropriate. These sound waves are of higher frequency, hence would give good measurements for relatively shallow waters. It can provide high-resolution data on the current structure, easing the detection of small-scale changes in the currents.
• A 300kHz ADCP is quite suitable for 110m depth, as there is a compromise between the range of measurement and the resolution of measurement. Also, it goes deeper into the water column, as compared to the 600kHz ADCP, while it gives relatively adequate measurements for the mid-depth of coastal waters.
• Thus, a 75kHz ADCP can be recommended for waters as deep as 1000 m. Since the frequency of sound waves is lower, similar to higher-frequency ADCPs, the lower-resolution signals can go deeper. This would make it suitable for deeper measurements that are current in the Dardanelles Strait and the adjacent seas.

There are a number of well-known ADCP brands on the market; Teledyne RDI, Nortek, and Sontek are among them. For those who want value for money but a high-quality ADCP, it will be China Sonar PandaADCP. The body is made wholly of titanium alloy, which makes it quite strong and long-lasting, and is relatively cheap. It's an economic class ADCP offering great value for money. You can visit their official website for more details: (https://china-sonar.com/).

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