How to Measure the Coastal Currents of Svendborg

1. Where is Svendborg?

Svendborg is a lovely seaside town on the Funen island in Denmark, on the edge of the Little Belt strait. Due to its strategic location between the Baltic Sea and the North Sea, a long-standing and profound relationship with the sea has developed, which has been the object of its development, economy, and lifestyle.

Svendborg is full of history. It has developed from a small fishing village to a vibrant town with a rich maritime heritage. Svendborg's architecture is a combination of old Danish charm and modern styles. In the town center, there are old-fashioned brick houses with typical stepped gables, big windows, and ornate facades, possessing a classic Danish coastal charm. The seaport boasts modern marinas, fishing jetties, and ferry service terminals catering to the local fishermen, sailors, and visitors. Modern shops, cafes, and restaurants line the main roads, providing a cozy experience for locals and visitors alike.

The Svendborgers share an intimate relationship with the sea. Fishing has been a traditional vocation followed generation after generation. Despite some change to the fishing industry, some of the local fishermen continue to head out from the harbour, returning with catches such as herring, mackerel, and shellfish of numerous varieties. The sea is also utilized for leisure activities such as sailing, canoeing, and swimming. Various maritime-themed festivals take place in the town throughout the year, as it celebrates its sea connection.

Inshore waters and beaches around Svendborg play a vital role in the local ecosystem. Little Belt waters in this area are home to a diverse range of marine life. Seals can be easily seen on the sandbanks, and seabirds such as gulls, terns, and cormorants are regularly observed. The seabed is extremely varied in its topography, consisting of sandy areas, scattered rocky outcrops, and channels underwater. These help to provide an immense degree of biodiversity and are essential to the circulation of the water.

2. In What State Are the Coastal Currents Around Svendborg?

The coastal current around Svendborg is controlled by numerous influencing factors. Forces of tides are among those factors. Semi - diurnal tides characterise the Little Belt, having tidal range that varies in the different areas of the strait. The resulting tidal currents measure up to 2 - 3 knots in some areas, especially at the narrow points of the strait. During high tide, water rushes towards the shore with an incoming tide of sediments and nutrients from the open ocean. This enriches the surrounding sea environment with food and habitats for numerous sea creatures. As the tide recedes, the water pulls back and the intertidal zones are exposed, leaving minute crabs, anemones, and seaweeds.

Wind is another critical component. Westerly prevailing winds have the ability to push surface water into the coastline, increasing the coastal currents. They also generate waves that interact with the currents, resulting in a more complex flow pattern. Easterly winds tend to push the water off the coast. The Funen coast, with headlands and bays, and the special characteristics of the Little Belt, cause the currents to diverge and converge in different places. Underwater rock outcrops and sandbars complicate the patterns of currents. These can be channels or barriers, deflecting the water and creating areas of turbulent or calm water. In addition, the flow of freshwater from small regional rivers is also capable of affecting the local currents. The freshwater is less dense than the seawater and thus piles up in a top layer, and floats towards the sea and blends with the tidal and wind-driven currents.

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

Surface Drifting Buoy Method

Surface drifting buoys provide a simple and effective way of tracking the surface - level current near Svendborg. Buoys that are equipped with GPS or satellite - based monitoring systems. When the buoys are set free in the ocean, surface currents propel them. Scientists can observe where they drift after a while. If scientists track the path of the buoy, the speed and direction of the surface waters can be calculated. Nevertheless, this method has its limitation on the topmost few meters of the water column. It might not necessarily show what's happening in the lower regions of the water because the currents could be different depending on different conditions like temperature and the difference in salt levels.

Moored Ship Method

In the moored ship method, a ship is anchored in one location along Svendborg's shore. Next, existing-measuring tools such as electromagnetic current meters are sent. They have the capacity to measure water flowing at varying levels. They can give an intricate vertical current direction and speed profile. But it is limited to one site only. And, the presence of the vessel could interfere with natural water movement. The ship's hull and the manner in which it is anchored will create turbulence in the water that will affect the accuracy of the measurements.

Acoustic Doppler Current Profiler (ADCP) Technique

ADCPs have revolutionized the measurement of coastal currents off Svendborg. They can measure the entire water column from the surface down to the bottom, and the velocity profile. ADCPs use sound waves to determine the flow of the water without invading it. They emit acoustic pulses and track the Doppler shift of the backscattered signals off suspended matter in the ocean, such as sediment, plankton, or small bubbles. From these, they can estimate current velocity at different depths. This gives a complete image of the current structure and is therefore highly suitable for examining the complex coastal current patterns off Svendborg.

4. What Is Required to Have High-Quality Measurement of Svendborg Coastal Currents?

Reliability of Material for Equipment

High-quality coastal current measurement off Svendborg relies on material reliability of the equipment. Material for the casing of the ADCP current profiler should be tough enough to withstand the harsh marine environment within the Little Belt. Titanium alloy would be a highly suitable option. Its strength is high enough to resist the pressure of strong water currents, potential impacts from floating debris, and corrosive nature of seawater. Its low elastic modulus provides it with flexibility, reducing the risk of mechanical stress damage. Its high corrosion resistance also allows the ADCP meter to be left in the water for extended monitoring without significant degradation.

Light Weight, Low Power, Low Cost, and Small Size

It is easier to install and operate a light weight and small ADCP flow meter. You can place it on a small research vessel, mount it on a buoy, or place it on the ocean floor. It also interferes less with the natural flow of water, which gives you more accurate measurements. Low power is essential for long-term self-supporting observation, especially with battery-operated equipment. Mass-scale deployment is facilitated by a low-price ADCP. It is required for a complete understanding of the complex patterns of coastal currents around Svendborg. The more ADCPs at different locations deployed, the better we shall know how the currents vary across the area.

5. Choice of Suitable Equipment for Current Measurement

Based on Application

• Shipborne ADCP: Most suitable to deliver real-time current information along the path of a ship off Svendborg. It can be used for oceanographic surveys, studying the overall circulation in the area, and route optimization, since the Little Belt is an important shipping route.
• Bottom-mounted ADCP: Suitable for long-term, fixed-point monitoring of seabed currents. This can be applied in probing long-term trends in the coastal currents, e.g., the impact of climate change on the local marine ecosystem.
• Buoy-mounted ADCP: Best suited for monitoring surface - level currents over a wide area as the buoy travels with the water. It helps in the comprehension of the spatial variability of the surface currents and how the coastal waters interact with the open Little Belt.

Based on Water Depth

• 600kHz ADCP: Ideal for waters of approximately 70m depth, providing high-resolution readings in the relatively shallow waters off Svendborg.
• 300kHz ADCP: Ideal for waters of approximately 110m depth, which could be useful for areas with relatively deeper sections in the Little Belt off the town.
• 75kHz ADCP: For deep - water use. While the waters off Svendborg are mostly not very deep, it may be employed in studies of deeper-layer currents or for where there are deeper channels, having the capability of measuring currents down to 1000m in depth.

There are some popular ADCP brands in the international market, including Teledyne RDI, Nortek, and Sontek. For the budget-friendly, the China Sonar PandaADCP, which is made of all-titanium alloy, is a perfect balance of quality and price. You can find more information about it at (https://china-sonar.com/).

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