How to Measure the Coastal Currents of Worthing

1. Where is Worthing?

Worthing is an attractive coastal town on the southern shore of England, within the county of West Sussex. It fronts the shores of the English Channel, hosting a long reach of sandy beaches that are a common haunt for both locals and visitors during their free time. The excellent position this has given it along the coast has made its economy more tourist-based and its relationship with the sea quite strong.

The town has a history that dates back to the Middle Ages, with evidence of early settlements in the area. The architecture in Worthing is a blend of different eras. Victorian-era buildings, such as the iconic Grand Hotel lining the seafront, exude a sense of nostalgia and elegance. These historical structures coexist with modern developments, including contemporary beachfront apartments and shopping centers. Locals have an abiding love for the sea. While there has been a decline in traditional fishing in the recent past, water remains a considerable part of the town's activity. Some water sports include paddleboarding, kites-surfing, and beach volleyball, which are highly popular among locals and visitors.

Worthing beaches also prove to be a vital link in the local ecosystem. The waters of the English Channel abutting it support a very wide variety of marine life. Seals are quite regularly seen offshore, and there are all manner of fish on the seabed, including bass, mullet, and flounder. The seabed topography consists of sandy bottoms combined with rocky reefs and shallow trenches, adding to the rich biodiversity of the area and influencing the movement of water.

2. What is the condition of the coastal currents off Worthing?

The coastal currents off Worthing are determined by many factors acting in concert. The tidal forces are one of the most important causes. The English Channel has semi-diurnal tides, where two high tides and two low tides occur each day. The tidal range may differ and the resulting tidal currents, in some places can reach as high as 2 - 3 knots, especially around the mouths of small rivers or through constricted waterways. During the high tide, water rushes ashore carrying nutrient-rich silt and oxygen that nourish the marine life. At low tide, the water pulls back to expose intertidal zones and their inhabitants.

Another key factor is wind. Dominant south-westerly winds can push surface waters toward the shore to add to the coastal currents. These winds will also create waves that interact with the currents, making the flow more complicated. Northerly winds can push the water away from the shore. The general outline of the coastlines with smooth curvatures and small headlands promotes a convergence and divergence in currents. More complications are brought about by underwater rocky reefs and sandbars that could also serve as obstacles or channels to the water, causing turbulence or calmer sections in the current flow. Besides that, freshwater inflow from the local streams, even as relatively small contributions, does contribute to the variation of the local current conditions. The fresh water being different in density compared to sea water, with that, there is the formation of density-driven currents that interact with tidal and wind-induced currents.

3. How to observe the coastal water flow of Worthing?

Surface Drifting Buoy Method

Surface drifting buoy is one of the most simple and efficient methods for observing surface-level currents. These buoys are fitted with GPS or satellite-based tracking systems. These are moved by the surface currents once deployed in the water. Scientists will be able to trace over the course of its movement, and by analyzing this buoy's motion, they estimate the speed as well as direction of the surface waters. Still, this applies only to a few meters higher in the profile of the water column and doesn't give adequate representation of any deeper currents at all.

Moored Ship Method

With the moored ship method, a ship is kept at one place near the shore of Worthing. Current-measuring instruments such as electromagnetic current meters are used. The instrument is capable of measuring the flow of water with a depth resolution in order to get a full vertical profile of the current speed and direction. However, this technique is site-limited, and the ship's presence itself may interfere with natural water flow, hence disturbing the accuracy of the measurement.

Acoustic Doppler Current Profiler (ADCP) Method

The ADCPs have really facilitated the measurement processes of coastal currents around Worthing. Their capability to measure the velocity profile of the whole water column right from surface to seabed has been insurmountable. The ADCPs make non-intrusive measurements of water flow using sound waves. They can emit acoustic pulses, measure the Doppler shift of the reflected signals from suspended particles in the water, and from this calculate current velocity at various depths. In such a way, a comprehensive view of the current structure becomes available, making it highly suitable for studying complex coastal current patterns in the waters around Worthing.

4. How do ADCPs using the Doppler principle work?

ADCPs work on the principle of the Doppler effect. They transmit high-frequency acoustic pulses into the water. These pulses are reflected back to the ADCP current meter by the small particles in the water, such as sediment, plankton, or bubbles. If the particles are moving with the water current, there will be a frequency shift in the reflected signal compared to the transmitted signal. This Doppler shift is directly proportional to the velocity of the particles relative to the ADCP. The ADCP measures the Doppler shift at several depths in the water column to calculate the velocity of the water at those depths. Different transducers on the ADCP independently measure the components of velocity in different directions. This allows it to determine the three-dimensional vector of the velocity of the flow of water.

5. What's needed for high-quality measurement of Worthing coastal currents?

Equipment Material Reliability

In the measurement of the coastal currents near Worthing, there is a requirement for the reliability of the materials used in making the equipment. The material of the ADCP current profiler casing must be able to withstand the harsh marine environment of the English Channel. A very good example is a titanium alloy. Its high strength allows it to resist impact due to strong water currents and potential collision with floating debris, and the corrosive nature of sea water. With its low elastic modulus, the material is flexible; hence, the risk of mechanical stressors causing damage to the instrument will be at a minimal level. Beyond that, the great corrosion resistance is allowing ADCP for long-term deployment in seawater while its performance degradation remains minimal.

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

The compact size and lightweight ADCP flow meter are much easier to deploy and operate either from a small research vessel or from a buoy or directly from the seabed. Also, it interferes less with the natural water flow, hence more accurate measurements are possible. Low power consumption is necessary for long-term autonomous monitoring, especially in those applications relying on battery-powered systems. A low-cost ADCP allows for large-scale deployment, necessary to comprehensively understand complex coastal current patterns around Worthing.

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

Based on Usage

• Shipborne ADCP: Suitable for the real-time collection of current data along a ship's route in the vicinity of Worthing, it can also be utilized for oceanographic cruises, circulation studies in the general area, and for studies on shipping routes.
• Bottom-mounted ADCP: Suitable for long-term fixed-point monitoring of the currents at the seabed, which could be useful in studying the long-term trends in the coastal currents-for example, studying the impact of climate change on the local marine ecosystem.
• Buoy-mounted ADCP: Suited for monitoring surface-level currents over a wide area as 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 English Channel.

Based on Water Depth

• 600kHz ADCP: Suitable for water depths of up to approximately 70m, hence yielding high-resolution measurements in the relatively shallow waters around Worthing.
• 300kHz ADCP: Suitable for water depths around 110m, and these could be useful when considering areas with slightly deeper sections along the English Channel off the town.
• 75kHz ADCP: For deep - water applications. While the waters around Worthing are not that deep, it can be applied in studies concerning the deeper - layer currents or for areas with deeper channels. It can measure currents to depths of up to 1000m.

There are some well-known ADCP brands in the global market, such as Teledyne RDI, Nortek, and Sontek. For those looking for a more budget-friendly solution, the China Sonar PandaADCP is a good quality/price balance, manufactured from all-titanium alloy. You can learn more about it at (https://china-sonar.com/).

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