How to Measure the Coastal Currents of Dunbar

1. Where is Dunbar?

Dunbar is a charming coastal town in East Lothian, Scotland. It is situated on the south coast of the Firth of Forth, bordering the North Sea. This glorious location has granted Dunbar a long history of connection with the sea, and it has shaped the development of the town and the life of its inhabitants.

The town is steeped in and has a long-established history. It was a large fishing and trading harbour in the past. It has evolved over the centuries but not lost its unique character. The houses in Dunbar are mixed in style. In the middle of the town, there are old-fashioned stone-built houses with the classic Scottish features. They have thick walls, small comfortable windows, and sloping roofs. There are newer buildings, too, mostly along the harbor and the center of the town. These include hotels, cafes, and shops serving the inhabitants and the traveling tourists. A combination of old and new structures gives a homey and hospitable atmosphere.

The people residing in Dunbar have a very close historical relation with the sea. Fishing has been an old-time profession here for generations upon generations. Although the size of the fishing industry has changed over the last few years, there are still some local fishermen who leave from the harbor. They come back with a variety of fish including cod, herring, and mackerel. The harbor is not only utilized for fishing boats. It's also popular among locals and tourists for short boat trips. The public may also enjoy the magnificent vistas of the Firth of Forth, whose peaceful waters are added to by the flight of seabirds overhead.

The beaches and coastline surrounding Dunbar are important to the local ecology. The Firth of Forth is a special area where freshwater from the rivers mixes with the seawater. This blend creates a rich diversity of sea habitat. There is a range of fish, seals, and the occasional dolphin present in the water. Seabed topography is varied in the region with sandy areas, rocky outcrops, and channels along the seabed. This area not only supports high levels of diversity, but it has a significant impact on the way the water flows.

2. What is the State of Coastal Currents Near Dunbar?

Different conditions influence the coastal currents in and around Dunbar. Tidal forces prevail. Semi - diurnal tides are found in the Firth of Forth, and two high tides and two low tides occur each day as a result. The tidal range is not consistent, and the tidal currents caused by this can have speeds ranging up to 2 - 3 knots in some areas. This is especially so at the mouths of estuaries or where the coas line adopts a characteristic form. Water rushes into the firth during high tide, with the open sea providing the firth with sediment and nutrients. This nourishes the surrounding marine ecosystem and provides food and habitat for many sea creatures. When the tide goes out, the water withdraws, and the area above high and low tides remains exposed. These areas are populated by small crabs, sea anemones, and a range of seaweeds.

Wind also plays a part. Strong south - westerly winds are capable of pushing surface water on to the shore, making the coastal currents stronger. Such winds also generate waves that take effect on the currents. The waves make the water move more complicatedly, with eddying and degrees of roughness. Northerly winds drive the water away from the coast. The shape of the coastline, its headlands, and bays, and the special characteristics of the Firth of Forth make the currents converge to some extent in some places and diverge to some extent in others. Sandbars and submerged rocky outcrops also help create even more complex current patterns. They either channel or shut off the water, changing the direction in which the water flows and creating pools where the water is smooth or turbulent. The local current patterns can also be changed by the fresh water entering from the rivers that feed into the Firth of Forth. The fresh water is lighter than the seawater, and thus it floats on top, moving towards the sea, mixing with the tides as well as with the currents generated by the winds.

3. Observation of Dunbar Coastal Water Flow

Method of Surface Drifting Buoy

Surface drifting buoys are an inexpensive but useful method of observing the flow of surface water in and around Dunbar. These buoys are satellite- or GPS-monitored. They drift off into the surface flow once you have thrown them in the water. We can watch them go wherever they go with time. You can make a good estimate as to how quickly the surface is moving and what direction it's moving if you examine what direction the current is flowing based on the direction in which the buoys go. This method doesn't say anything more than the surface upper few meters of water, though. It might not reveal what's happening in the lower parts of the water, as the current there could be another due to variables like changes in temperature and salinity levels.

Moored Ship Method

Using the moored ship method, a ship is moored to a specific location off Dunbar's coast. Then, there are instruments like electromagnetic current meters used to monitor the flow of water. These devices can also measure how the water is flowing at various levels. This gives a detailed picture of how fast the water is flowing and in which direction at different levels. But this method can be applied only at one place. Additionally, the presence of the ship there can distort the natural flow of the water. This can make the measurements less accurate because the ship's hull and how it is moored can create ripples in the water.

Acoustic Doppler Current Profiler (ADCP) Method

ADCPs have transformed the measurement of the coastal currents off Dunbar. They are able to measure the speed of the water flowing from the surface to the seafloor. ADCPs gauge the flow of the water through sound waves without stopping it. They send out sound pulses and measure the way the sound changes when it bounces off small objects underwater, like sediment, plankton, or minute bubbles. They can then work out how fast the water is moving at different depths. This gives them a whole picture of the way the currents are organized, so it's great for looking at the complex coastal current patterns off Dunbar.

4. How Do ADCPs That Operate on the Doppler Principle Work?

ADCPs work based on the Doppler effect. They send out high-frequency sound pulses into the water. As the pulses come into contact with small objects in the water, e.g., sediment, plankton, or bubbles, these objects bounce back the sound signals to the ADCP. When these small things are moving with the water current, the frequency of the returning sound will be other than that of the transmitted sound. The difference in frequency is directly proportional to how fast the small things are moving compared to the ADCP. By feeling this shift in frequency at different depths of water, the ADCP can measure how rapidly the water is moving at each of these depths. The ADCP contains several pieces that can feel the velocity in different directions. This helps establish how the water is moving in three - dimensional space, and it gives a complete description of how the water is moving.

5. What Do Dunbar Coastal Currents Require to be Measured at a High Quality?

Reliability of Equipment Material

To effectively measure the coastal currents off Dunbar, equipment material is quite important. The outer part of the ADCP needs to be made of material that can be durable enough in the harsh North Sea and Firth of Forth marine environment. Titanium alloy is a great choice. It's very durable, so it can withstand breaking by strong currents of water and can resist probable collisions with floating objects as well as with the sea water that's salty and corrosive. It's also relatively elastic, which minimizes the chances it will break because of the impact of huge forces. And it won't rust fast, so the ADCP can operate in the sea for a long duration without weakening.

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

It is easier to install and maintain a light and small ADCP. You can attach it to a small research ship, suspend it from a buoy, or install it on the seafloor. It also does not disturb the natural water flow as much, so that the readings are more accurate. Saving power is important, especially if it is battery powered and needs to run independently for long periods. A cheap ADCP allows us to deploy many of them. This is absolutely essential to be able to fully understand the complex coastal current dynamics in and around Dunbar. The more ADCPs we have distributed in different locations, the better we can map how the currents change across the area.

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

Based on Usage

• Shipborne ADCP: Great for acquiring current data directly as a ship moves near Dunbar. You can utilize it to study the ocean, see how the water moves typically in the area, and enhance shipping routes if there are any around.
• Bottom-mounted ADCP: Is best for monitoring seabed currents for an extended period of time at the same site. It is very handy to see how the coastal currents change over a prolonged time span, e.g., how climate change affects the sea environment along the coast.
• Buoy - mounted ADCP: Suited to study the surface - level currents of a large area as the buoy is transported by the water. It tells us how the surface currents change at different places and how the waters along the coast become mixed up with the open North Sea.

Based on Water Depth

• 600kHz ADCP: Suitable for water that's around 70m deep. It can provide very precise measurements in the shallower waters off Dunbar.
• 300kHz ADCP: Ideal for water that's around 110m deep. This can be used in the Firth of Forth off the town where the water is slightly deeper in certain areas.
• 75kHz ADCP: Intended for use in deep-water areas. While the sea at Dunbar is not deep in the majority of the area, it can be used for investigation of deeper-layer flows or for deep channels. It can read as deep as 1000m.

There are several well-known ADCP manufacturers on the international market, and some of these are Teledyne RDI, Nortek, and Sontek. For anyone seeking a cheaper one, ADCP supplier China Sonar PandaADCP, which is made of all-titanium alloy, is a quality-price ratio balance. Further information can be accessed at (https://china-sonar.com/).

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