How can we measure the coastal currents of Clacton-on-Sea

1. Where is Clacton-on-Sea?

Clacton-on-Sea is a coastal town on the east coast of England, within the county of Essex. It lies on the North Sea coast, with a long sandy beach that has made it a popular seaside resort. This prime coastal location has not only drawn in tourists but also shaped the town's long-standing connection to the sea.

The town was documented from the time of the Roman era and proved to have very early settlements by archaeological findings. The architecture of Clacton-on-Sea is rather diversified. There coexist Victorian-era buildings, which include the immense Pavilion building that was once prominent, along with modern developments featuring contemporary beachfront apartments and business structures. There is an important affinity between this local community and the ocean. Fishing has been a traditional occupation, and although the fishing industry has evolved, there is still a small fishing fleet operating from the town's pier. The port area also serves as a hub for pleasure boating, with many locals and tourists enjoying trips along the coast.

The beaches of Clacton-on-Sea are not only a recreational destination but also an important part of the local ecosystem. The shallow waters of the North Sea host many different marine species: most often offshore, one can notice seals, and there are even fish such as bass, flounder, and mackerel in the seabed. The topography of the seabed itself includes expanses of sand, rocky outcrops, and shallow trenches that help to contribute to this biodiversity but also feature in the movement of water.

2. What are the conditions for the coastal currents around Clacton-on-Sea?

The coastal current conditions around Clacton-on-Sea present a very multifaceted effect due to so many factors interacting with each other. Tidal forces are some of the influential factors. Tides in the North Sea follow a semi-diurnal pattern. The tidal range can vary, and the resulting tidal currents can reach speeds of up to 2-3 knots in some areas, especially near the mouths of small rivers or in areas where the coastline constricts the water flow. During high tide, water surges towards the shore, bringing in nutrients and sediment from the open sea. With retreating water levels during low tide, the intertidal areas are exposed where a number of shore-living organisms exist. Wind is the other important driving force. When south - westerly winds prevail, surface waters are blown towards the coastline, increasing coastal currents. Surface waves generated can interact with coastal currents to cause a more intricate flow pattern. Northerly winds can move the water off the shore. The shape of the coastline, with its bays, headlands, and the relatively flat Essex coast, tends to converge and diverge the currents. Underwater rocky outcrops and sandbars further complicate the current patterns. These can act as a barrier or channel to the flow of water, producing areas of turbulence and calm. Additionally, the inflow of freshwater from local rivers, like the River Stour, can affect the local current patterns. The freshwater has a different density compared to the seawater, leading to the formation of density - driven currents that interact with the tidal and wind - induced currents.

3. How to observe the coastal water flow of Clacton-on-Sea?

Surface Drifting Buoy Method

Drifting buoys are simple tools but efficient to observe surface currents. They usually come with either GPS or satellite-based tracking system systems. These buoys, once dropped into the ocean, drift because of the water movement at their surface. They can then be followed in their movements over a certain period by scientists. In this way, it is possible to estimate how fast and in which direction the surface waters move. However, this method is limited to the upper few meters of the water column and may not accurately represent the deeper currents.

Moored Ship Method

In the moored ship method, a ship is anchored at a specific location near Clacton - on - Sea's coast. Current - measuring instruments, such as electromagnetic current meters, are then deployed. These instruments can measure the flow of water at different depths, providing a detailed vertical profile of the current velocity and direction. But this method is restricted to a single location, and the presence of the ship can potentially disrupt the natural water flow, affecting the accuracy of the measurements.

Acoustic Doppler Current Profiler (ADCP) Method

ADCPs have revolutionized the measurement of coastal currents near Clacton - on - Sea. 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 water flow. 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 provides a comprehensive view of the current structure, making it highly suitable for studying the complex coastal current patterns in the waters around Clacton-on-Sea.

4. How do ADCPs using the Doppler principle work?

ADCPs operate based on the Doppler effect. They emit high-frequency acoustic pulses into the water. When these pulses encounter small particles like sediment, plankton, or bubbles in the water, the particles reflect the acoustic signals back to the ADCP profiler. If the particles are moving with the water current, there will be a shift in the frequency of the reflected signal compared to the transmitted signal. This Doppler shift is directly proportional to the velocity of the particles relative to the ADCP. By measuring the Doppler shift at different depths in the water column, the ADCP meter can calculate the velocity of the water at those depths. Multiple transducers on the ADCP are used to measure the velocity components in different directions, allowing for the determination of the three-dimensional velocity vector of the water flow.

5. What is required for high-quality measurement of Clacton-on-Sea coastal currents?

Reliability of Equipment Material

Reliability of the equipment materials is vital for high-quality measurement of the coastal currents around Clacton-on-Sea. The casing of the ADCP flow meter should be made from a material that can withstand the harsh marine environment of the North Sea. Titanium alloy is an excellent choice. Its high strength allows it to resist the impact of strong water currents, potential collisions with floating debris, and the corrosive nature of seawater. Its low elastic modulus provides flexibility, reducing the risk of damage from mechanical stress. Moreover, its outstanding corrosion resistance ensures that the ADCP current meter can be deployed in seawater for long - term monitoring without significant degradation.

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

A compact and lightweight ADCP current profiler is easier to install and operate, whether on a small research vessel, attached to a buoy, or placed on the seabed. It also has less impact on the natural water flow, leading to more accurate measurements. Low power consumption is essential for long-term autonomous monitoring, especially when relying on battery-powered systems. A low-cost ADCP enables large-scale deployment, which is necessary for comprehensively understanding the complex coastal current patterns around Clacton-on-Sea.

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

Based on Usage

• Shipborne ADCP: Ideal for obtaining real-time current data along a ship's route near Clacton-on-Sea. It can be used for oceanographic surveys, studying the general circulation in the area, and for optimizing 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 surface-level current monitoring 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: Suitable up to about 70m depths, and provide high-resolution measurement in the somewhat shallow waters by Clacton-on-Sea.
• 300kHz ADCP: Would be suitable in about 110m depth environments, which should be useful areas with slightly deeper sections in North Sea near to the town.
• 75kHz ADCP: Designed for deep-water applications. Although the waters near Clacton-on-Sea are generally not extremely deep, it can be used for studies related to the deeper-layer currents or for areas with deeper channels, capable of measuring currents at depths of up to 1000m.

There are some famous brands in the world market, like Teledyne RDI, Nortek, and Sontek. For customers who want a cheap but good-quality ADCP, China Sonar PandaADCP, made of all-titanium alloy, has a very good balance between quality and price. You can check it out at  https://china-sonar.com.

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