How to measure the Coastal Currents of Sinan?

1. Where is Sinan?

Sinan is one county in South Jeolla Province, South Korea, with its place on the southwestern part of the Korean Peninsula. It is an area rich in natural beauty and endowed with abundant maritime resources. It consists of a large number of islands and a very long coastline, hence a very peculiar coastline.

The islands of Sinan are of very varied landscapes, from sandy beaches, which run along the shores and form a perfect place for beach-goers and water sports fans, to rocky cliffs and coves along the coastline, adding up to the area's scenic beauty. The local population is engaged in fishing and aquaculture. The Yellow Sea near Sinan is a semi-enclosed sea with a rich variety of marine life.

The sea off Sinan provides a lifeline for people living there. The waters are rich in fish species like flounder, sea bass, and various shellfish. Seaweed beds are present too, although their status and condition could be crucial because it was not only one part of a marine ecosystem but also an important component to the locals' economy. Sea conditions mostly determine the climate of a place since they bring a cool breeze toward land from the sea in summer. It moderates temperature changes throughout a year.

2. What is the condition of coastal currents around Sinan?

Multiple factors come into play to determine the nature of the coastal currents around Sinan. One such important constituent force is the tidal current. The tidal range in the Yellow Sea is considerable, and the flow of the tide and the ebb produce a very complicated pattern of currents. Water enters and leaves the bays and straits between the islands, giving rise to dynamic flow.

It is also affected by the coastline shape and underwater topography significantly. The presence of any island, shallow areas, and underwater ridges may bend the course of currents and alter their velocity. For example, the water may flow faster through narrow channels between islands or slow down when it spreads over a wide shallow area. Besides, wind patterns, especially the seasonal winds blowing across the Yellow Sea, may drive surface currents and affect the mixing of different layers of water. Inflow of fresh water from local rivers and streams can also change the salinity and density of the coastal waters, hence affecting the flow of the current.

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

Surface Drifting Buoy Method: These buoys are thrown into the water, letting the surface current be observed while the buoy drifts. The buoy is followed at regular time intervals using GPS systems or other tracking systems of position. However, some drawbacks exist with this particular method. It will estimate only the surface current and is essentially dependent on wind and wave actions. For instance, if a strong wind blows the buoy in a different direction from the actual current, it can result in incorrect measurements of the direction and speed of the current.

Anchor - Boat Method: The current can also be measured by an anchored boat. Instruments are lowered into the water from the boat to measure the current at various depths. While this is good for more detailed depth-wise measurements, it has some disadvantages. The position of the boat is fixed; hence, the area of measurement is restricted, and currents over a large coastal area may not be fully represented.

This Acoustic Doppler Current Profiler method falls as quite improved to measure coastal currents. Using ADCPs involves the projection of sound waves in the water whose reflected Doppler shift was measured and computed for its velocity at each depth: thus providing a better resolution or record of current right from surface waters to the seabed bottom. ADCPs are less affected by surface disturbances and can operate continuously for long periods, giving a more accurate picture of the current structure.

4. How do ADCPs using the Doppler principle work?

ADCPs work based on the Doppler effect. They transmit high-frequency acoustic pulses into the water. When these pulses interact with moving water particles, the frequency of the reflected pulses is changed. If the water particles are moving towards the ADCP profiler, the reflected signal frequency is higher than the emitted one; if they are moving away, it's lower.

The ADCP meter has multiple transducers that send and receive signals at different angles. It can calculate the three-dimensional velocity of the water by analyzing the Doppler shifts coming from different directions and at different depths. This means that it can determine the horizontal and vertical components of the velocity, providing a thorough understanding of the structure and behavior of the current.

5. What needs to be done for high quality Sinan coastal current measurement?

The equipment should be made of appropriate, reliable materials for high-quality measurement of the currents near Sinan. A robust casing will be required because of the saltwater, possible storm exposure, tide, and island influences. The size of the equipment should be small in order to make deployment and recovery easy, considering the very complex coastal landscape with a lot of islands and channels.

While its construction must be lightweight for ease in handling the equipment during installation and maintenance, it should consume low power to enable long-term and autonomous operation. The latter two should be cost-effective for large-scale measurements.

The casing of ADCPs is preferably made of titanium alloy. The corrosion resistance of a titanium alloy is excellent, which is vital in withstanding the corrosive effects of sea water. It is strong and durable to bear the pressure of the water at different depths. Its lightweight nature makes it more convenient for various deployment methods.

6. How to Choose the right equipment for current measurement?

First, the purpose of using the equipment should be considered in choosing the equipment for current measurement at Sinan. The most suitable equipment would be a ship-mounted ADCP flow meter if the measurement is solely used for the navigation of vessels or short-term research purposes, as it provides current information in real time during the voyage itself.

For measurements near the seabed, such as in applications related to sediment transport or benthic ecology, a bottom-mounted ADCP would be preferable since it captures details in the near-bottom current. On the other hand, when there is a need for long and wide-area monitoring of coastal currents, then a buoy-type ADCP current profiler will serve best.

Regarding the frequency of ADCPs, a 600kHz ADCP is a good choice for water depths up to 70m, while for water depths up to 110m, a 300kHz ADCP will be more appropriate. In waters deeper than 1000m-as may be found near Sinan-a 75kHz ADCP is recommended.

There are well - known ADCP current meter brands such as Teledyne RDI, Nortek, and Sontek. However, a Chinese brand, China Sonar PandaADCP, is also worth considering. It is made of all - titanium alloy material and offers an excellent cost - performance ratio. You can find more information on their website: https://china-sonar.com/.

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