How to Measure the Coastal Currents of Tenby

1. Where is Tenby?

Tenby is a picturesque seaside town in Pembrokeshire, Wales, on the south coast of the Bristol Channel. Its strategic location has provided it with an age-old and intimate relationship with the sea, which has significantly influenced its development, economy, and lifestyle of its inhabitants.

Tenby is rich in history. It has been a seaside resort for centuries, with a history of maritime trade, fishing, and tourism. The town's architecture is a quaint mixture of Georgian and traditional Welsh architecture. There are old-fashioned stone-built houses with typical features in the town center. They typically have solid, thick walls, small-sized windows, and slate roofs, with a quintessential Welsh seaside feel. Tudor-style and medieval town walls add to its historic feel. Along the seashore are newly built modern hotels, cafes, and restaurants to cater for the massive throngs of visitors who descend upon Tenby each year.

Tenby folk have a traditional and long - established love of the sea. It is a traditional mode of work passed down from generation to generation. Although change over time has impacted on the fishing community, local fishermen still set out to sea from the harbour. They bring back species of fish and shellfish like mackerel, bass, and various shellfish. The harbour is not only a hub for fishing but also a popular point for boat outings. People are able to breathe in the crisp sea air, the sight of seagulls flying overhead, and the picturesque scenery of the Bristol Channel.

The waters and beaches that are found around Tenby are critical to the area's environment. The Bristol Channel waters within the area are home to a large diversity of sea life. Seals may typically be seen on the sandbanks, and seabirds such as gulls, terns, and cormorants are often around. The sea bed is topographically intricate, with sandy patches, scattered rock outcrops, and submerged channels. These are richly populated with a diverse life and play an important part in driving the water.

2. What's the Status of the Coastal Currents Off Tenby?

Sea currents off the coast at Tenby are determined by a range of factors. Tidal forces are one of the prominent determining factors. The Bristol Channel has a massive tidal range with semi-diurnal tides. The tidal currents generated thus can be extremely high, in some instances even as much as 3 - 4 knots in specific locations, mainly around the narrow entrances as well as around headlands. Since tide is high, water washes ashore along with attendant nutrients and sediments from open ocean. They nourish the indigenous marine community by providing nutrients as well as habitat for various sea creatures. As the tide recedes, the water flows out and intertidal places become filled up with tiny crabs, anemones, and other types of seaweeds.

Another thing of paramount significance is wind. Dominant south - westerly winds have the potential to drive surface waters against the coast and increase the coastal currents. The winds also generate waves that interfere with the currents, and this results in a more complicated flow pattern. Northerly winds can force water off the shore. The headlands and bays of the Pembrokeshire coastline and the nature of the south - west Welsh coast mean that the currents diverge and converge at some points. There are submarine rocky outcrops and sandbars that further complicate the currents. These then form channels or barriers, redirecting the water flow and creating areas of quiet or disturbed water. Besides, the fresh water supply from small local streams can affect the local currents. The fresh water is lighter than seawater and thus forms a layer over it, flowing into the sea and mixing with the tidal and wind-driven flows.

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

Surface Drifting Buoy Method

Surface drifter buoys are simple and effective means of tracking surface - level current near Tenby. The buoys utilize the GPS or satellite - based system for locating. Once released into the sea, the surface currents carry them. The researchers track their path over time. From the path covered by the buoy, they can measure the speed and direction of surface waters. Although, this method has a drawback only to the upper few meters of water column. It might not be depicting what is happening in the deeper areas of the water where the currents could be different due to different reasons like temperature and alteration in salinity.

Moored Ship Method

In the moored ship method, a ship is anchored at a certain point near Tenby's shore. Then, present-measuring instruments like electromagnetic current meters are employed. These instruments can measure the flow of water at different depths. They provide an accurate vertical profile of the direction and speed of the current. But this method is restricted to a single point. Also, the ship can in fact disrupt the natural flow of water. The ship's hull and the manner in which it is moored can create turbulence in the water, which can affect the accuracy of the measurements.

Acoustic Doppler Current Profiler (ADCP) Method

ADCPs have revolutionized coastal current measurement off Tenby. They can measure the velocity profile of the entire water column from the surface to the seabed. ADCPs use sound waves to non-intrusively measure the flow of the water. They emit acoustic pulses and measure the Doppler shift of the backscattered returns off suspended particles in the water, such as sediment, plankton, or small bubbles. From these, they can calculate the current velocity at different depths. This gives a full description of the current structure and is thus very well suited to exploring the complex coastal current regimes off Tenby.

4. What is Needed for High-Quality Measurement of Tenby Coastal Currents?

Equipment Material Reliability

In high - quality measurement of coastal currents off Tenby, equipment material reliability is of prime concern. The casing of the ADCP profiler needs to be of a material that will withstand the harsh marine environment of the Bristol Channel. Titanium alloy is best. Its high strength allows it to resist the pressure of strong water currents, potential impact with floating debris, and the corrosive nature of seawater. Its low elastic modulus gives it flexibility, reducing the likelihood of damage from mechanical stress. Moreover, its high corrosion resistance allows the ADCP to be submerged in the water for prolonged periods of observation without significant degradation.

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

The ADCP flow meter will be lighter and smaller in size, so it will be easier to install and service. You can place it on a small research vessel, mount it on a buoy, or install it on the seabed. It will also disrupt the natural current to a lesser degree, hence providing better readings. Low power usage is required for long - term autonomous surveillance, especially in the situation of employing battery - powered equipment. Low-cost ADCP allows for extensive deployment. This is needed to gain a good understanding of the complex coastal current patterns around Tenby. As more ADCPs are deployed elsewhere, we are able to have a better appreciation of how the currents vary across the region.

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

Based on Use

• Shipborne ADCP: Suitable for obtaining real-time current data along a ship path near Tenby. It can be used for oceanographic surveys, studying the general circulation in the area, and streamlining shipping routes, if any, in the area.
• Bottom-mounted ADCP: Suits long-term, fixed-point observation of seabed currents. It is appropriate for the study of long - term trends in coastal currents, e.g., climate change impact on the local marine ecosystem.
• Buoy-mounted ADCP: Well adapted to observing surface - level currents over a large area as the buoy moves with the water. It facilitates the understanding of the spatial variation of the surface currents and the exchange between the coastal waters and the open Bristol Channel.

Based on Water Depth

• 600kHz ADCP: Appropriate for approximately 70m water depths, providing high-resolution readings in the comparatively shallow seas off Tenby.
• 300kHz ADCP: Appropriate for water depths of approximately 110m, which would be useful for slightly deeper areas off the town in the Bristol Channel.
• 75kHz ADCP: For deep-water operations. Although the waters around Tenby are in general not particularly deep, it could be utilized for research on the deeper - layer currents or for locations with deeper channels, and it can measure currents up to 1000m deep.

There are several well-known ADCP brands in the global market, such as Teledyne RDI, Nortek, and Sontek. If you need a cost-effective model, the China Sonar PandaADCP, made of all - titanium alloy, is a good compromise between quality and price. You can learn more about it at (https://china-sonar.com/).

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