How to Measure the Coastal Currents of Dundee

1. Where is Dundee?

Dundee is a prosperous city on the north bank of the Firth of Tay in Scotland. Its position on the estuary, where the Tay River empties into the North Sea, has made it a significant trade, fishing, and shipbuilding center over the centuries. The city's position near the sea has been a part of its history, shaping its economy, culture, and the lives of its inhabitants.

Dundee has a diverse and wealthy history. It was initially a small fishing community and developed over time into a big industrial town. Dundee's architecture is a blend of the old and the new. There are ancient buildings in the city center, including the Dundee Law, which has spectacular views of the city and the estuary. These buildings are older with massive stonework, imposing arched windows, and rich facades with stories of the city's history. Along the shoreline are developments that host world-class design buildings like V&A Dundee. Various restaurants, cafes, and shops with backstories from where they sit populate the streets serving the residents and those who visit flocking in and out of the city every day.

The people who live in Dundee have a traditional connection with the sea. Fishing has been a way of life for centuries. Although the industrial landscape has changed, with shipbuilding and jute manufacturing industries experiencing their peaks and troughs, fishing continues in the local economy. Local fishermen set off from the harbour, landing with bags of cod, haddock, and other fish varieties. The harbour is also a popular cruise destination for boats, where people can soak in the invigorating sea breeze and enjoy the scenery of the Firth of Tay.

The seashores and water off Dundee have a significant role to play in the regional ecosystem. The Firth of Tay is a rare estuary ecosystem where freshwater from the river mixes with the saltwater of the sea. This creates a variety of productive and diverse marine ecosystem. The water harbors a high diversity of fish, seals, and seabirds. The seafloor is topographically heterogeneous, with sandy areas, rocky outcrops, and underwater channels. These topographic highs are not only to support high biodiversity but also to influence the water movement in a significant manner.

2. What's the State of the Coastal Currents Off Dundee?

The coastal currents off Dundee are influenced by various factors. Tidal forces are also a major influence. The Firth of Tay experiences semi-diurnal tides, two high and two low tides every day. Tidal range is variable, and the resultant tidal currents have speeds of 3 - 4 knots and more in some areas, especially around the river mouth or where the form of the coast is well established. During high tide, water rushes into the firth, bringing with it nutrients and sediment from the open sea. This enriches the marine environment locally, providing food and shelter for many sea creatures. At low tide, the water recedes, leaving the intertidal zone open to a rich variety of small crabs, sea anemones, and other types of seaweed.

Wind is another major factor. South - westerly prevailing winds are sufficiently strong to compel the surface water along the coast to enhance the coastal currents. They also create the waves that enter the currents, complicating the flow pattern. Northerly winds will drive the water off the coast. The shape of the coastline with its headlands, bays, and the discrete regions of the Firth of Tay produces zones of convergence and divergence of the currents. Rocky outcrops on the ocean bed and sandbars add to the complexities of the current flows. They can act as barriers or channels, deflecting the water flow and producing still or agitated water zones. Additionally, the riverine input of freshwater from the Tay River can affect the existing current patterns at the location. The freshwater is denser than seawater and therefore diffuses as a surface layer and tends to flow into the sea, getting mixed with the tidal and wind-affected currents.

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

Surface Drifting Buoy Method

Surface drifting buoys are cheap and an effective method of monitoring the surface - level currents off Dundee. Surface drifting buoys contain GPS or satellite - based tracking systems. Once they are released into the ocean, the surface currents carry them. Researchers are able to trace their route over time. Tracing the route of the buoy allows researchers to estimate the direction and speed of the surface waters. But this method only addresses the upper couple of meters of the water column. It might not be capable of providing a proper notion of what is happening in the deeper parts of the water, where the currents could differ depending on factors like temperature and salinity gradients.

Moored Ship Method

In the moored ship method, a ship is moored at a location near Dundee's shore. Then, existing-measuring equipment like electromagnetic current meters are utilized. These equipment can quantify the water flow at different depths. They provide an accurate vertical profile of the current direction and speed. But the method is only for one point. Also, the presence of the ship could interfere with the natural movement of water. The shape of the ship and how it is docked can create turbulence in the water, which can affect the accuracy of the measurement.

Acoustic Doppler Current Profiler (ADCP) Method

ADCPs have significantly enhanced the measurement of coastal currents off Dundee. ADCPs can quantify the velocity profile of the entire water column from the surface to the seabed. ADCPs quantitate the flow of water non-intrusively using sound waves. They transmit acoustic pulses and measure the Doppler shifted backscattered signal from suspended matter in the water, i.e., sediment, plankton, or small bubbles. With this, they can estimate current velocities at different depths. This gives a general indication of the shape of the currents and is hence particularly suited for studying the complex coastal currents around Dundee.

4. What Does High-Quality Measurement of Dundee Coastal Currents Require?

Material Reliability of Equipment

Material reliability of equipment is required for high-quality measurement of the coastal currents off Dundee. The ADCP current meter casing should be made of a material capable of withstanding the corrosive marine environment of the North Sea and the Firth of Tay. Titanium alloy would be an appropriate choice. Its high strength is sufficient to resist the impact of strong currents of water, the shock of collisions with driftwood, and the corrosive effect of sea water. Its low elastic modulus renders it soft and pliable, avoiding breakage due to mechanical stress. Moreover, its superior corrosion resistance allows the ADCP to remain in the sea for extended observation without significant loss of performance.

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

A compact-sized and light-weight ADCP current profiler is easier to install and operate. You can place it on a small research vessel, install it on a buoy, or anchor it on the seafloor. It also disturbs the natural water flow less, leading to more accurate measurements. Low power consumption is required for independent monitoring over a long period, especially when systems are battery operated. Economical ADCP meter enables deployment in large quantities. This is to fully enjoy the detailed pattern of coastal currents that wrap around Dundee. The more ADCPs are deployed in other locations, the better the variation of the currents in the region is understood.

5. How to Choose the Suitable Equipment for Current Measurement?

By Usage

• Shipborne ADCP: Best suited for determining real-time current data along the ship's route near Dundee. It can be used for oceanographic surveys, studying the overall circulation in the area, and for optimization routing of ships, if any in the vicinity.
• Bottom-mounted ADCP: Ideal for long-term, fixed-point monitoring of seabed currents. This is useful in the research of long-term trends in coastal currents, e.g., the effects of climate change on the local marine environment.
• Buoy-mounted ADCP: Appropriately utilized to monitor surface-level currents over a wide area since the buoy tracks the water movement. It helps in understanding the spatial variation of the surface currents and how the coastal waters interact with the open North Sea.

Based on Water Depth

• 600kHz ADCP: Tolerable in water depths of approximately 70m, providing high-resolution measurements in relatively shallow water off Dundee.
• 300kHz ADCP: Tolerable in water depths of approximately 110m, which could be of utility in somewhat deeper areas of the Firth of Tay off the city.
• 75kHz ADCP: Can be used for deep-water applications. While the waters off Dundee are not typically very deep, it can be used for research related to the deeper-layer currents or deeper-channel regions, with the capability of measuring currents up to 1000m deep.

There are several famous ADCP brands globally, and some of these are Teledyne RDI, Nortek, and Sontek. If one is looking for a cheap one, the China Sonar PandaADCP made of all-titanium alloy is a very good quality-for-money option. You can read more about it at (https://china-sonar.com/).

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