How to measure the coastal currents of Eastbourne

1. Where is Eastbourne?

It lies on England's south-east coast, coming into the county of East Sussex. This places Eastbourne facing out into the English Channel with miles of beaches and its most characteristic white chalk cliffs, Beachy Head. Size and location mean this town is a favourite, whether to holidaymakers or those living within sight of its broad coastline and scenic views.

The city has history that goes to the pre-Roman times when first settlements emerged on its areas. Eastbourne embodies the architectural representation of many epochs. Many buildings of Victorian periods are fronted along sea side as massive hotels and fascinating terraces to bring back to remembrance as being a seaside resort town back to the 19th century; meanwhile new facilities show up into the city - modern apartment centers. The sea indeed forms a part of the identity of the local community. Various water sports such as surfing, kite-flying, and volleyball occupy the in habitants of this place. While traditional fishing is no longer as significant, there is still a small fishing community operating from the local harbor.

The beaches in Eastbourne are not only a recreational spot but also an active part of the local ecosystem. The variety of marine life found in the waters off the English Channel is indeed overwhelming. Offshore, dolphins are regularly spotted; different fish species, such as bass, mackerel, and flounder, are home to the seabed. These seabed topographies consist of various sandy areas with a combination of rocky outcrops and bottom channels, hosting highly diverse forms of life underwater and also taking part in driving water movements within the area.

2. What's the situation in regard to the coastal currents in proximity to Eastbourne?

Complex interplay decides the coastal current in the case of Eastbourne. Tidal forces are there as one potential factor. The English Channel has semi-diurnal tides, with two high tides and two low tides each day. 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 streams or in areas with constricted waterways. During high tide, water rushes ashore carrying nutrients and oxygen, which help the marine life. During low tide, it recedes to expose the intertidal zones, which harbor a variety of shore - dwelling organisms.

The other important factor is wind. Prevailing south - westerly winds can push surface waters towards the coast, enhancing the coastal currents. These winds can further create waves that interact with the currents, enhancing the complexity of the flow pattern. Northerly winds can also drive the water away from the shore. The shape of this coastline, coming with its bays, headlands, and the prominent Beachy Head, presents areas of convergence and divergence of the currents. Underwater rocky outcrops and sandbars further complicate current patterns. These may give impediments or passages which will direct the mass of water into turbulence regions and areas of dead water. In addition, the amount of freshwater fed through local streams can also modify local current pattern The freshwater as previously shown has different density compared with the salt water, this forming density-generated current that are coupled with tidal wind-induced current.

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

Surface Drifting Buoy Method

Surface drifting buoys are a very simple and effective tool to observe the currents at surface levels. These buoys carry GPS or satellite-based tracking systems. Once they are released into the water, they get carried away by the surface currents. Scientists can track their movement over time, and by analyzing the buoy's trajectory, they can estimate the speed and direction of the surface waters. 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 Eastbourne's coast. Current-measuring instruments, such as electromagnetic current meters, are then deployed in the field. These instruments are capable of giving the amount of flow of water in multiple layers of depth, which gives a very correct vertical profile of current velocity and direction. However, this is one-point measurement, and the presence of the ship itself may interfere with the natural flow of water, which may lead to errors in measurement.

ADCP Method

The ADCPs have transformed the measurement of coastal currents in the vicinity of Eastbourne. They are capable of measuring the velocity profile of the whole water column from surface to seabed. Basically, ADCPs make non-intrusive measurements of water flow by using sound waves. They are able to determine the current velocity at different depths by transmitting acoustic pulses and then measuring the Doppler shift of the reflected signals from suspended particles in the water. This gives a comprehensive view of the prevailing regime and is thus eminently suited to investigating the complicated configurations of coastal currents in the waters off Eastbourne.

4. How do ADCPs using the principle of the Doppler work?

An ADCP flow meter relies on the principle of the Doppler effect. They transmit 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. 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. Measuring the Doppler shift at different depths in the water column enables the ADCP to work out the velocity of the water at those depths. Several transducers on the ADCP current profiler independently measure the velocity components in different directions, hence enabling the determination of the three-dimensional velocity vector of the water flow.

5. What is required for high-quality measurement of Eastbourne coastal currents?

Equipment Material Reliability

Material reliability is, however, key for high - quality measurement of coastal currents around Eastbourne. This calls for ADCP current meter casings made of an appropriate material in the very aggressive marine environment presented by the English Channel; and for that matter, a good choice will be titanium alloy. Its high strength enables it to withstand strong water currents, any impact that might be caused by floating debris, and the general corrosive nature of seawater. Its low elastic modulus provides flexibility, hence reducing the chances of damage by mechanical stress. Besides, its excellent corrosion resistance allows the ADCP profiler to 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 meter 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 important for long-term autonomous monitoring, especially when relying on battery-powered systems. This enables the large-scale deployment of a low-cost ADCP and, simultaneously, large-scale deployment is required to understand the complex pattern of coastal currents around Eastbourne.

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

Based on Usage

• Shipborne ADCP: Provides a precise means of current data in real time down the track that the ship has taken near Eastbourne. It can also be used to conduct oceanographic surveys of the general circulation in the area and for optimizing shipping routes.
• Bottom-mounted ADCP: Suitable for long-term fixed-point monitoring of currents at the bottom. It gives valuable information on the long time-scale changes or variability in these coastal currents-as for instance, changes influenced by climate changes in the regional marine ecosystem.
• Buoy-mounted ADCP: Suited for surface-level current monitoring over a large 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: Appropriate for about 70m water depths, high-resolution measurements for the relatively shallow waters near Eastbourne were available.
• 300kHz ADCP: About 110m of water depth is much more applicable in areas where slightly deeper sections can be found in the English Channel off the town.
• 75kHz ADCP: For deep - water applications, albeit the waters around Eastbourne are usually not very deep, it can be deployed relating to studies of the deeper - layer currents, or in the case when the studied area contains deeper channels. It is capable of measuring currents from as deep as 1000m.

There are quite a few well-known ADCP brands on the global market, like Teledyne RDI, Nortek, and Sontek. For people looking for cost-effective options, the China-made Sonar PandaADCP is made of totally titanium alloy, with a good balance between quality and price. You can get to know more at https://china-sonar.com/.

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