How are we going to measure the coastal currents of Great Yarmouth?

1. Where is Great Yarmouth?

Great Yarmouth is located on the east coast of England, in Norfolk County. Due to its position at the mouth of the River Yare onto the North Sea, it is a very well-placed town that has had a very substantial port for several centuries, great for fishing, trade, and lately tourism.

History

The history of the town dates back to the Anglo-Saxon period. Archaeological remains indicate that this was an important settlement even then, and proximity to the sea would have allowed early maritime activities. The architecture in Great Yarmouth is eclectic, featuring building types from various ages. There are medieval - style buildings in the old town area, characterized by narrow, winding streets and ancient churches. Other Victorian-era structures like the grand Britannia Pier also dot the seafront, a testament to the popularity of the town as a seaside resort in that era. These coexist with modern buildings, including contemporary hotels and shopping centers. The locals have a very strong attachment to the sea. Fishing has been one of the mainstays of the local economy for many years. The fishing fleet is no longer so busy as it was, but what remains brings in large quantities of cod, herring, and plaice, and there is also pleasure boating and a town which tourists visit every year to appreciate the beaches, the pier, and many other attractions along the coast.

The beaches of Great Yarmouth are not only a popular tourist destination but also an important part of the local ecosystem. The adjacent waters of the North Sea are home to a diverse range of marine life: seals can often be seen lounging on the sandbanks offshore, while the seabed is populated by various fish species, as well as crustaceans like crabs and lobsters. The seabed topography includes sandy areas, rocky outcrops, and underwater channels, which provide not only a variety of ecological habitats but also determine the flow of water.

2. What is the situation of the coastal currents close to Great Yarmouth?

The coastal currents close to Great Yarmouth are determined by a very complicated interaction of influences. Tidal forces are predominant. The tide in the North Sea is semi - diurnal, with two high and two low tides each day. There can be up to a substantial tidal range, notably at the mouth of the River Yare. Resulting tidal streams can reach up to 3 - 4 kts in some places. At high tide, water comes into the estuary and up the coast and carries with it nutrient-rich sediments from the open ocean; at low tide, the waters retreat to uncover the intertidal zones seething with life.

Wind plays a very major role. For one, sustained south-westerly winds would be able to push surface waters towards the coastline, enhancing current action along that coast. These winds also form waves interacting with the currents to provide a much more complex flow pattern. Northerly winds can push the water away from the shore. The shape of the coastline, with its bays, headlands, and the river estuary, causes the currents to converge and diverge. Further complication of current patterns is created by the underwater rocky outcrops and sandbars. Such features can act both as obstacles or conduits, while water is deflected in its course, thus creating areas of turbulence and tranquility. Furthermore, the input of fresh water from River Yare may alter the local current patterns. Since freshwater has a different density than seawater, density-driven currents can form and also interact with the tidal and wind-induced ones.

3. How to observe the coastal water flow of Great Yarmouth?

Surface Drifting Buoy Method

Surface drifting buoys are a cheap and efficient means for observing surface-level currents. Basically, these buoys are fitted with GPS or satellite-based tracking systems. Once thrown into the water, they are conveyed by surface currents. Knowing this, scientists can see how it has traveled over time, and by following the path the buoy has taken, they can calculate the approximate velocity and direction of surface waters. This technique is basically confined to the top few meters of the water column and can very well be unrepresentative of deeper currents.

Moored Ship Method

This technique involves a ship anchored at a place situated closely opposite the coast of Great Yarmouth. Current measuring instruments, like electromagnetic current meters, are then deployed. These instruments can measure the flow of water at different depths and provide a detailed vertical profile of the current velocity and direction. However, this method is restricted to a single location, and the presence of the ship may disrupt the natural water flow and hence affect the accuracy of measurement.

Acoustic Doppler Current Profiler (ADCP) Method

Since then, ADCPs have transformed the technology used to measure coastal currents off Great Yarmouth. They are able to measure the velocity profile of the entire water column from the surface to seabed. An ADCP current meter works by non-intrusively measuring the water flow by sending out sound waves into the water. By emitting acoustic pulses and measuring the Doppler shift of the reflected signals from suspended particles in the water, they can calculate the current velocity at different depths. This allows a holistic approach toward the present structure and hence makes it one of the highly appropriate devices to study the prevailing complex current systems along the shores around Great Yarmouth.

4. How Do the ADCPs Employing Doppler Principle Work?

Doppler principles lie at the center of operation in an ADCP current profiler. These are used for producing high-frequency sound bursts underwater. These pulses, upon hitting the small particles suspended in the water-like sediment, plankton, or bubbles-reflected acoustic signals are received by the ADCP. When the particles move with the water current, the reflected signal would experience a shift in frequency compared to the transmitted one due to Doppler shift. The Doppler shift will be proportional to the velocity of the particle with respect to the ADCP. A measurement of the Doppler shift at different depths in the water column enables the ADCP to calculate the velocity of the water at those depths. Because there are multiple transducers on one ADCP profiler, measuring different directions of flow, one can resolve a three-dimensional velocity vector for water flow.

5. What is needed for quality measurement of currents along the coast of Great Yarmouth?

Reliability of Equipment Material

Since these are high-measurement, accurate, and important coastal currents around Great Yarmouth, a lot of the equipment material used has to be highly reliable. The casing on the ADCP flow meter should be designed to resist extreme marine conditions like those in the North Sea, and the material of choice for this purpose can be titanium alloy. Its high strength enables it to withstand strong water currents, possible collision with floating debris, and the corrosive nature of seawater. The low elastic modulus imparts flexibility to the material, reducing the possibility of damage due to mechanical stress. In addition, its excellent corrosion resistance allows the ADCP to be deployed in seawater for long-term monitoring without significant degradation.

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

Compact and light, an ADCP meter is thus more easily set up and put to work: whether on a small research vessel, attached to a buoy, or on the seabed itself. It acts with minimal invasion into the water flow and less turbulence of water masses, giving better accuracy for measurement. The power consumption rate being low contributes much in support of long-term autonomous monitoring with battery-powered systems. The low-cost ADCP will enable the deployment on a large scale, which is quite necessary for the comprehensive understanding of the complex coastal current patterns around Great Yarmouth.

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

Based on Usage

• Shipborne ADCP: This equipment provides an effective basis for obtaining, in real time, actual current data alongside a ship track near Great Yarmouth and can serve during general oceanographic cruises aimed at studying general circulations and further optimization of shipping routes.
• Bottom-mounted ADCP: Suitable for long-term, fixed-point monitoring of the currents at the seabed. This is valuable for studying long-term trends in the coastal currents, such as the impact of climate change on the local marine ecosystem.
• Buoy-mounted ADCP: Suited for monitoring surface-level currents over a wide area while the buoy drifts with the water. It helps in understanding the spatial variability of the surface currents and how the coastal waters interact with the open North Sea.

Based on Water Depth

• 600kHz ADCP: Shallower water of up to about 70m provides high-resolution measurements in the fairly shallow waters close to Great Yarmouth.
• 300kHz ADCP: For depths of about 110m, which is appropriate for slightly deeper sections that can be encountered along the North Sea near the town.
• 75kHz ADCP: For deep-water applications, though the waters around Great Yarmouth are generally not extremely deep, it can be utilized for studies associated with deeper-layer currents or areas with deeper channels and is capable of measuring currents at depths of up to 1000m.

There are several well-known ADCP brands in the global market, such as Teledyne RDI, Nortek, and Sontek. For those seeking a cost-effective option, the China Sonar PandaADCP, made of all-titanium alloy, offers a great balance of 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.