How do we measure the currents around Lowestoft coastline

1. Where is Lowestoft?

Lowestoft is a seaside town in the eastern county of England, in Suffolk. It stands at the very east of England on the north bank of the North Sea. Due to this prime location, it has served as a primary port for fishing, shipping, and recently for the renewable industry.

The town owns history back in the Anglo - Saxon times. Archaeological findings point towards an early settlement due to fishing and trade dealings. The building architectural style at Lowestoft features a mix between old and new architecture. Indeed, there exist historic buildings found in the city centre, most dating from the 17 Century that feature traditional Suffolk brick. Alongside these are Victorian-era structures, such as the elegant Royal Plain, modern industrial buildings, and modern estates of private housing. The local community has a deep-rooted connection to the sea.

For generations, fishing has been one of the mainstays of the local economy. Although the fishing industry has not been as buoyant in recent years, the town still maintains a small but active fishing fleet, bringing in fish such as cod, herring, and mackerel. The port of Lowestoft also acts as a base for a variety of vessels, including pleasure boats and ships involved in the offshore energy sector.

The beaches of Lowestoft are neither solely a sightseeing venue, nor are they merely attractive for visitors but rather form a part of the local ecosystem. The adjacent waters of the North Sea are home to a diverse array of marine life: it is possible to see seals quite often on the sandbanks offshore, while the seabed itself is home to different species of fish, besides crustaceans and mollusks. The seabed topography consists of sandy areas, rocky outcrops, and underwater sandbars, which contribute to the rich biodiversity of the area and also influence the movement of water.

2. What is the situation of the coastal currents near Lowestoft?

The coastal currents near Lowestoft are influenced by a complex interplay of multiple factors. Tidal forces are a dominant factor. There is a semi - diurnal tide in the North Sea: on every day two high waters and two low waters can be recorded. Sometimes large tidal range effects may have consequential strong tidal streams, up to 3 or 4 knots in certain locations, which often occurs near the mouth of River Waveney discharging in the North Sea near Lowestoft. During high tide, water surges towards the shore, bringing in nutrients and sediment from the open sea. When low tide occurs, the water recedes and exposes intertidal zones where a great variety of shore-dwelling organisms exist.

The other important aspect is wind. The prevailing south-westerly winds are capable of pushing surface waters towards the coast, thereby enhancing the coastal currents. Associated with these winds, waves are generated. In interaction, these can complicate the current pattern. The northerly winds move the water offshore. The shape of the coastline, particularly the bays, headlands, and the distinctive shape of the Lowestoft Ness, tends to converge and diverge the currents. Adding to the complication in the current patterns are the underwater rocky outcrops and sandbars. Such features can provide a barrier or channel to deflect the water and produce regions of turbulence and calm. In addition, the input of fresh water from River Waveney may affect the local current patterns due to differences in density from the density of seawater. Density-driven currents form by virtue of these different densities which interact with the tidal and wind-induced currents.

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

Surface Drifting Buoy Method

Surface drifting buoys are simple and fairly reliable means to observe surface-level currents. They are fitted with GPS or satellite-based tracking systems. Once the buoys are released in the water, they are conveyed by the surface currents. Scientists are therefore able to document its movement in a series; thus, it gives them a capability to measure the buoy's trajectory with approximate speed and direction of surface waters. However, this technique works in the top few meters of the water column and might be unrepresentative of deeper currents.

Moored Ship Method

The method of the moored ship simply anchors a ship in a specified position over the seabed, off Lowestoft's coast. The current measuring instruments, such as electromagnetic current meters, are then deployed. These instruments can measure the flow of water at different depths, thus giving a detailed vertical profile of the current velocity and direction. This method is restricted to only one location, and the presence of the ship itself may interfere with the natural flow of water and hence the accuracy of the measurements.

Acoustic Doppler Current Profiler (ADCP) Method

A whole new revolution in measuring the currents near Lowestoft coastline has occurred, using ADCPs. They can obtain the velocity profile of the entire column of water up to seabed levels. ADCPs use sound waves to non-intrusively measure the water flow. They calculate the velocity of current at different depths by emitting acoustic pulses and comparing the Doppler shift of the reflected signals of suspended particles in water. This provides a full overview of the present structure and is therefore highly suitable for studying the complicated coastal current patterns in the waters around Lowestoft.

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

The ADCPs make use of the Doppler effect to work. They send high-frequency acoustic pulses into the water. When these pulses encounter small particles in the water, such as sediment, plankton, or bubbles, the particles reflect the acoustic signals back to the ADCP. If the particles are moving with the water current, a shift in frequency of the reflected signal will occur relative to the transmitted signal. This Doppler shift is directly proportional to the velocity of the particles relative to the ADCP meter.

The ADCP measures the Doppler shift at different depths in the water column and, hence, calculates 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 good-quality measurement of Lowestoft coastal currents?

Reliability of Equipment Material

For high measurement qualities of the coastal currents near Lowestoft, the reliability of the equipment materials is essential. The casing of the ADCP must be of a material which will withhold the harsh marine environment of the North Sea, which is titanium alloy. Its high strength can endure the impact of strong water currents, the potential impacts of floating debris, and the corrosive nature of seawater. Its low elastic modulus provides it flexibility, even in terms of mechanical stress damage risk. In addition to that, its outstanding corrosion resistance ensures long - term monitoring using ADCP profiler in seawater without significant degradation loss.

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

A smaller and lighter ADCP flow meter is much easier to install and perform operations, whether on a small research vessel, attached to a buoy, or even mounted on the seabed. It also has lower influence on natural water flow. Such an ADCP thus provides a more accurate measurement. Low power consumption is essential for long - term autonomous monitoring, especially when relying on battery - powered systems. A low-cost ADCP, however, opens the possibility for a large deployment strategy necessary in thoroughly understanding complicated coastal current patterns around Lowestoft.

6. Selection of Appropriate Current Measuring Instrument: How To?

Application-based

• Shipborne ADCP: Ideal for providing real - time current data along a ship's route near Lowestoft. These can be used for oceanographic surveys, studying the general circulation in the area, and optimisation of shipping routes.
• Bottom-mounted ADCP: Suitable for long-term, fixed-point monitoring of the currents at the seabed. This is valuable in studying the long-term trends in the coastal currents, such as the impact of climate change on the local marine ecosystem.
• Buoy-mounted ADCP: Very good for monitoring the current at the surface over a wide area while the buoy itself drifts with the water. It helps understand the spatial variability of the surface currents and the interaction of the coastal waters with the open North Sea.

Based on Water Depth

• 600kHz ADCP: Suitable for water depths up to about 70m, yielding high-resolution measurements in the relatively shallow waters near Lowestoft.
• 300kHz ADCP: Suitable for water depths around 110m, which can be useful for areas with slightly deeper sections in the North Sea near the town.
• 75kHz ADCP: For deep-water applications, though generally the waters around Lowestoft are not deep, it can still be used for studies relating to deeper-layer currents or for areas with deeper channels, able to measure currents from as low as up to 1000m.

There are quite a few big brands in the global market. Some of them are Teledyne RDI, Nortek, and Sontek. For cost-effective versions, the all-titanium alloy China Sonar PandaADCP is a pretty good balance between quality and price. You can find more details at (https://china-sonar.com/).

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