How to Measure the Coastal Currents of St Just

1. Where is St Just?

St Just is a coastal town in Cornwall, England, lying on the western tip of the peninsula, sharing its border with the Atlantic Ocean. Its physical location has nurtured a long - standing and profound connection with the sea that has been the focus of its development, economy, and day - to - day life of the inhabitants.

St Just boasts a rich heritage. It has a rich heritage based in the mining industry, specifically tin and copper mining, which thrived here for centuries. The St Just architecture is a blend of Cornish charm and the legacy of its industrial heritage. There are old stone-built houses at the town center with typical thick walls, small windows, and slate roofs, which provide a typical Cornish seaside atmosphere. There are also traces of abandoned mining-related structures, such as engine houses and mine shafts, that remind one of the town's industrial heritage. Down the main streets, new restaurants, cafes, and shops have opened their doors, catering to both the local residents and those tourists attracted by the town's history and natural environment.

The people of St Just have a deeply - rooted affinity with the sea. Although the economy of mining has declined, the sea is still a big part of the local economy and culture. Fishing has provided a secondary means of livelihood to some of the residents, where fishermen come in with catches ranging from mackerel, sardines, and other types of shellfish. The ocean also offers opportunity for water-based tourism activities. Boat cruises are popular, allowing one to feel the freshness of the sea air, observe the sight of seabirds such as gulls, terns, and cormorants flying over, and watch the beautiful view of the Atlantic Ocean.

The coast runs south from St Just and on and past Porthcurno to Pednvadan. The sea and beaches off St Just are critical habitats for the local ecosystem. The marine fauna of Atlantic Ocean waters here is varied. Seals are often found on sandbanks and rocky outcrops, and there is a varied morphology of the seabed, with sandy patches, large boulders, and sub-seabed channels. This provides varied and rich habitats to sustain an enormous number of species of crustaceans, fish, and marine vegetation.

2. What is the Condition of the Coastal Currents Around St Just?

The coastal currents around St Just are influenced by several factors. Tidal forces are among the most important factors. The Atlantic Ocean experiences semi - diurnal tides, with two highs and two lows daily. The tidal range in this region is quite large, and the tidal currents caused by this can be up to 2 - 3 knots in some areas, especially at the narrow inlets and headlands. During high tide, water washes up on the shore carrying nutrients and sediments from the open sea. This supports the marine ecosystem in the area by providing nutrients and homes to other sea creatures. When the tide is out, the water recedes, and intertidal regions are exposed, with little crabs, sea anemones, and other forms of seaweed.

Wind is also a vital factor to consider. Strong south - westerly winds can push surface water towards the shore, causing stronger coastal currents. The winds also generate waves that combine with the currents, creating a more complex flow pattern. North-bound currents can force the water off the shore. The unique shape of the Cornish coast around St Just, with numerous headlands, bays, and the projecting western end, causes the currents to converge and diverge in different parts. Underwater rocky outcrops and sandbars also cause the current routes to be more tortuous. These can be barriers or channels, deflecting the flow of water and creating areas of stagnant or turbulent water. Furthermore, the entry of freshwater from small local streams into the sea can affect the local regime of currents. The freshwater is less dense than seawater and therefore forms a surface layer and flows seaward, mixing with the tidal and wind-driven currents.

3. Monitoring the Coastal Water Current of St Just

Surface Drifting Buoy Method

Surface drifting buoys are a simple and effective way to track the surface - level current near St Just. Surface drifting buoys are equipped with GPS or satellite - based tracking equipment. Once they are released on the water, the surface currents carry them away. Scientists can track their trajectory over time. They are able to approximate the speed and direction of the surface waters by analyzing the trajectory of the buoy. The method, however, can only be applied to the top few meters of the water column. It won't necessarily present an accurate indication of what is happening in the deeper areas of the water, where the currents could be fluctuating depending on factors like shifts in temperature and salinity.

Moored Ship Method

In the ship moored method, a ship is moored at a point off St Just's coast. Current-measuring instruments like electromagnetic current meters are then lowered there. The instruments can measure the movement of water at different depths. They provide a good vertical profile of the speed and direction of the current. But the method is only applicable to one location. In addition, the existence of the vessel is also bound to interfere with the natural water flows. The hull design of the ship and its mooring lead to turbulence in the water that will have an effect on the accuracy of the measurements.

Acoustic Doppler Current Profiler (ADCP) Method

ADCPs have been used to change dramatically the measurement of coastal current flow off St Just coast. ADCPs can measure the velocity profile throughout the water column from surface to bed. ADCPs utilize sound waves to estimate the water current non-intrusively. They emit acoustic pulses and measure the Doppler shift of the returned signals from suspended matter in the water, such as sediment, plankton, or small bubbles. Based on this, they can calculate the current velocity at different depths. This gives an overall view of the current setup, which is highly appropriate to explore the complicated coastal current patterns along St Just.

4. What is Needed in High-Quality Measurement of St Just Coastal Currents?

Equipment Material Reliability

Equipment material reliability is essential in high-quality measurement of coastal currents along the coast of St Just. The ADCP current meter casing must be made of material strong enough to withstand the harsh marine environment of the Atlantic Ocean. An example of good material would be titanium alloy. Its strength allows it to endure the pressure of strong water currents, potential impacts from floating debris, and the corrosive nature of seawater. Its low elastic modulus makes it flexible and reduces the risk of damage from mechanical stress. In addition, its superior corrosion resistance allows the ADCP meter to be left in situ for extended monitoring without losing its initial characteristics.

Light Weight, Small Size, Low Power, and Low Cost

A light-weight and small-size ADCP flow meter is easier to install and operate. You can place it on a small research vessel, install it on a buoy, or lay it on the ocean floor. It also creates less interference with the natural water flow and thus provides more accurate measurements. Low power consumption is needed for extended - term autonomous monitoring, especially when employing battery - based systems. Large - scale deployment is possible with a low - cost ADCP. It is needed in order to completely understand the complicated coastal currents off St Just. With more ADCPs spread out at different locations, we can better see how the currents vary throughout the area.

5. How to Choose Suitable Equipment for Current Measurement?

Depending upon Application

• Shipborne ADCP: Ideally used to obtain current data in real-time along the track of a vessel near St Just. It could be used to carry out oceanographic surveys, studying the large-scale circulation within the area, and shipping route optimization, if any, around the area.
• Bottom-mounted ADCP: Suitable for long - term, fixed - point monitoring of seabed currents. This is applicable for the observation of long - term trends in the coastal currents, e.g., climate change impact on the marine ecosystem of the region.
• Buoy-mounted ADCP: Appropriate for observing surface-level currents over a large area since the buoy is transported with the water. It helps in understanding the spatial variability of the surface currents and how coastal waters exchange with the open Atlantic Ocean.

Based on Water Depth

• 600kHz ADCP: Appropriate for water depths of a maximum of about 70m, providing high-resolution outputs in the comparatively shallow Atlantic waters surrounding St Just.
• 300kHz ADCP: Appropriate for water depths of about 110m, which would be used in regions with slightly deeper spots in the Atlantic Ocean surrounding the town.
• 75kHz ADCP: Deep-water version. While the waters around St Just are not usually very deep, it is usable for investigation in regard to the deeper-layer currents or to deeper channel zones, and it is capable of measuring up to 1000m depth currents.

There are several well - known ADCP manufacturers in the global market, such as Teledyne RDI, Nortek, and Sontek. For budget-conscious individuals, the China Sonar PandaADCP, all - titanium alloy, is a great compromise of quality and price. You can learn more at (https://china-sonar.com/).

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