Measuring the Coastal Currents of Makarska?

1. Location of Makarska

Makarska is an attractive coastal town along the Dalmatian Coast facing the Adriatic Sea, Croatia. Located at such a place, the perfect proportions it gives to its natural charm and cultural wealth have made it the right destination both for locals and tourists.

Geographically, Makarska is situated between the Biokovo Mountain range and the Adriatic Sea. The Biokovo Mountains, with their towering peaks and rugged terrain, create not only a dramatic backdrop to the city but also influence local weather patterns. The mountains can act as a barrier to certain winds, which in turn impacts the wind-driven coastal currents.

The city is deeply rooted in maritime heritage, and the natives have an extremely deep attachment with the sea as fishing and sailing traditions are common in every second family here, being passed through generations. This old town in Makarska is quite pretty, full of narrow, stone-streeted streets and a lot of ancient buildings. Quite historic and culturally sounding, very often local festivities are celebrating these traits of this city that was maritime in earlier times.

Following the sea coast, Makarska is decorated with a multitude of bays and small coves. In the northbound direction from the city along the coast, the coastline bends somewhat inward and thus protects this coastline from rough waters. In a southerly direction, the sea opens onto the expanse of the Adriatic. Seabed diversities close to Makarska are made up of areas with sandy bottoms, rocky reefs, and underwater caves, hosting rich marine life.

2. What about coastal currents off Makarska?

The coastal currents off Makarska result from some quite complex interaction introduced by more factors. Wind is a primary driver. There is variability in the wind over the Adriatic Sea. A northwesterly wind, common during the summer months and known as maestral, may push surface waters toward the coast to create strong onshore currents. These onshore currents can bring in warmer waters from the open sea and transport nutrients, benefiting the local marine ecosystem.

On the other hand, the bora-a cold northeasterly wind-may cause the water to move offshore. The bora is generally stronger and more sudden than the maestral, with significant impact on the currents, especially during the winter when it is more frequent.

Tidal forces also play a role, although the tides in the Adriatic Sea are relatively small compared to some other regions. They still contribute to the overall movement of the water, with the ebb and flow of the tides affecting the direction and speed of the coastal currents.

Other crucial ones include the nature of bathymetry. In this area, the seafloor with all its irregular features, submerged cliffs, and ocean ridges acts to accelerate or decelerate and change directions of the current. To further illustrate this point, there may be small channels between outcrops that act to reduce cross-sectional flow and thus enhance speed.

River runoff from the nearby rivers is not as crucial as in some other areas but can be of some significance. During heavy rain, freshwater from the rivers reaches the coastal zone. This could alter the density of the seawater and produce density-driven currents. These interact with the larger-scale wind- and tide-driven currents, making the flow patterns even more complex.

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

Surface Drifting Buoy Method

A very simple but rather effective method for the initial understanding of the surface level of the coastal currents is the approach of a surface drifting buoy. Small-sized buoys with appropriate tracking devices, like GPS, are let into the water. Since they would be carried by the currents, their movement is monitored over time. By studying the path that the buoy took, scientists are able to approximate the speed and direction of the surface currents. This method has its drawbacks. The buoys are in the mercy of surface winds, which may take them out of the actual path of the current. Also, they give information concerning only the surface layer and not the deeper - layer currents.

Anchored Ship Method

The anchored ship itself can be used as a fixed platform to measure currents. The ship can suspend current meters at different levels from it. The records of velocity and direction are obtained on these meters at each depth. This gives all the information about the vertical profile of the currents at one position. It, however, has severe limitations regarding area coverage. It is only representative data from the immediate area around the ship, and the ship itself can potentially disrupt the natural flow of the water.

ADCP Method

Acoustic Doppler Current Profiler (ADCP) has become one of the preferred methods for measuring coastal currents near Makarska. ADCPs use sound waves to measure the velocity of water simultaneously at multiple depths. They can be deployed from ships, moored to the seabed, or attached to buoys, enabling more comprehensive data gathering. ADCPs are less affected by disturbances at the surface, such as wind, and thus are more accurate with respect to 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 using the Doppler principle work?

The ADCPs work on the principle of the Doppler effect. When an ADCP current meter sends high-frequency sound waves into the water, the waves encounter tiny particles in the water, like plankton, sediment, or even small bubbles. These particles scatter the sound waves back towards the ADCP. The frequency of the scattered sound waves received by the ADCP current profiler is different from that of the emitted waves. This frequency shift-the Doppler shift-is directly proportional to the velocity of the particles, and thus the water, relative to the ADCP.

Most ADCPs have multiple transducer beams. By calculating the Doppler shift in each beam, it is able to determine the various velocity components of the water in different directions. The ADCP flow meter can then proceed and calculate three-dimensional velocity of the water by vector addition of these velocity components. This would be able to provide a great view of how the water is moving in all directions and therefore very important for mapping the coastal currents with great precision.

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

Equipment Material Reliability

In the light of high-quality measurements in Makarska's coastal waters, the casing material of ADCP is considered crucial. For that, Titanium alloy is a great choice for the casing. The corrosion resistance of the Titanium alloy is outstanding, which is very much required as the equipment will be constantly exposed to the corrosive seawater. It can resist short- and long-term immersion in the salty environment without significant deterioration, which secures the ADCP's endurance and stability. Besides, this high strength-to-weight ratio also allows the ADCP to preserve its structural rigidity even during strong currents and rough seas.

Size, Weight, and Power Consumption

The ADCP meter should be small in size and light in weight. A compact design makes deployment in various settings easier. For example, it can easily be installed on a small research vessel or buoy. A smaller size minimizes the impact on the flow field being measured. Another important factor is low power consumption, enabling the ADCP to run for extended periods without needing frequent battery replacements or external power sources. This is especially important for long - term deployments in the often - remote coastal areas around Makarska.

Cost-effectiveness

This ADCP profiler can only allow large-scale and integral monitoring of Makarska's coastal currents if it is economically viable. With a lower-priced ADCP, the possibilities for more research institutions, environmental monitoring groups, and even local initiatives to afford equipment for data gathering are opened. This will, in turn, contribute to much more frequent data collection, very useful in the comprehension of complex coastal current dynamics.

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

Based on Usage Purpose

• Shipborne ADCP: This type of ADCP is fitted onto a moving ship. It is ideal for carrying out large-scale surveys of the currents in the coastal areas. While the ship moves along the coast, the shipborne ADCP is able to continuously measure the currents and thus provides a broad-scale view of the current patterns over an enormous area. It is useful during preliminary research or when studying the variations of the currents over wide geographical areas.
• Bottom-Mounted ADCP: These are usually installed on the seafloor. Bottom-mounted ADCPs would thus be available for long-term fixed-point measurements. They are capable of supplying real-time, uninterrupted information at one depth and position. The benefit of that would be substantial for the research on local hydrodynamics-for instance, to show how the current behaves at some bay or at some topographical feature under water.
• Buoyant ADCP: Buoyant ADCPs are attached to a floating buoy and thus can 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

• In waters shallower than 70m, the suitable option would be the 600kHz ADCP. Because the sound waves are of a higher frequency, this will work quite well in waters that are shallow. It allows for very high-resolution current structure data, and small-scale variations in the currents are much more easily detectable.
• A 300kHz ADCP will suit for approximately 110m of water depth, because this would then allow for the optimal compromise in terms of a trade-off between the measurement range and resolution; thus, better resolution with increased water column penetrations, relatively to the previously discussed 600kHz ADCP.
• In that respect, a better option for deeper waters of up to 1000m is the 75kHz ADCP. For the deeper parts, the sound waves have lower frequency, hence could pierce further but probably at a lower resolution compared to the higher frequency ADCPs. That makes it good for measuring the currents in deeper parts of Adriatic Sea near Makarska.

Several good ADCP brands exist on the market; there are Teledyne RDI, Nortek, and Sontek among the top. 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.