How can we measure the Coastal Currents of Incheon?

1. Where is Incheon?

Incheon is a bustling metropolis in South Korea, which is located on the northwest coast of the Korean Peninsula, fronting the Yellow Sea. It is an important transportation center and a major port city.

The cityscape of Incheon is both modern architecture and natural beauty combined. It has a sprawling port area, which is one of the busiest in the country, having a huge cargo transit and acting as a facilitator for international trade. Besides the port area, there are beautiful coastal areas, including sandy beaches and tidal flats. The local population is engaged in a wide range of activities such as shipping, fishing, and various service industries related to the port and tourism.

The Yellow Sea near Incheon is a semi-enclosed sea, generally quite shallow and host to a wide variety of marine life. It provides a home for a multitude of fish species, including flounder, anchovy, and small sharks. Large sheets of seaweed and beds of shellfish are common. The tides have a large impact on the coastal area of Incheon, with quite a large tidal range making the water ebb and flow, thus affecting the local environment and the coastal currents.

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

The coastal currents around Incheon are influenced by many aspects. Tidal currents are one of the predominant influences. The big tidal range in the Yellow Sea brings about the complication of current patterns while water moves in and out during the rise and fall of tides. The shape of the coastline and the underwater topography are very important. Incheon's coastline has bays, estuaries, and channels, and the presence of underwater sandbars and shoals can cause the currents to change direction and speed.

The inflow of rivers and other freshwater sources can affect the salinity and density of the coastal waters, which influences the current flow. The wind pattern, especially seasonal winds from the northwest and southeast, can drive surface currents and affect the mixing of different water layers. The shipping activities in the port can also have a minor impact on the local currents through the movement of ships and the displacement of water.

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

Surface Drifting Buoy Method: A surface - drifting buoy can be released into the water to observe the surface current. The buoy's movement is tracked over time using GPS or other tracking systems. However, this method also has its own limitations. This is because it only gives the surface current and is sometimes affected by wind and waves. For instance, the buoy might be blown in a different direction by a strong wind from the actual direction of the current, hence measuring the wrong direction and speed of the current.

Anchor - Boat Method: The current can be measured by an anchored boat. Instruments are lowered from the boat into the water to measure the current at different depths. While this allows for more detailed depth - wise measurements, it also has drawbacks. The fixed position of the boat restricts the area of measurement, and it may not capture the full variability of the currents in a large coastal area.

Acoustic Doppler Current Profiler (ADCP) Method: This method of measurement is quite advanced and efficient in the measurement of the coastal currents. The ADCPs emit an acoustic signal into the water and, based on the return signals and their Doppler shift, calculate the velocity of the water at various depths, providing a complete profile from surface to seabed. 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 on the principle of the Doppler effect. They transmit high-frequency acoustic pulses into the water. When these pulses encounter moving water particles, the frequency of the reflected pulses is altered. If the water particles are moving towards the ADCP, then the frequency of the reflected signal is higher than the emitted one; if they are moving away, it is lower.

The ADCP has multiple transducers that send and receive signals at different angles. By processing the Doppler shifts from different directions and at different depths, the device calculates the three-dimensional velocity of the water. This means it can calculate the horizontal and vertical components of the velocity, giving a very detailed understanding of the current structure and behavior.

5. What is necessary to conduct a high-quality measurement of Incheon coastal currents?

For high-quality measurement of coastal currents near Incheon, the equipment needs to use reliable materials. With regard to the marine environment featuring saltwater, possible direct exposure to storms, or influence of tides and river inflows, a tough casing is crucial. Small in size for easy laying and retrieval of the equipment is essential in the sea area, where the shape of the coastal landscape complicates matters further with many ports, bays, and channels.

A lightweight design is preferable in order to make the equipment easily manageable during installation and maintenance periods. Low power consumption to enable long-term autonomous operations. Cost-effectiveness due to the large scale that measurements will be made at.

The casing of ADCPs is preferred to be made of Titanium alloy. Titanium alloy features excellent corrosion resistance, important for withstanding the corrosive effects of seawater. It is also strong and durable to resist pressure at different depths of water. Its lightweight nature makes it more convenient for various deployment methods.

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

When choosing equipment for current measurement near Incheon, first consider the purpose of use. If it is to be used for a vessel's navigation or short-term research, a ship-mounted ADCP will be suitable. It provides real-time current information during the voyage.

For measurements near the seabed, such as for studying sediment transport or benthic ecology, a bottom - mounted ADCP is preferable. It can capture the details of the near - bottom current. If long - term and wide - area monitoring of the coastal current is required, a buoy - type ADCP is ideal.

Regarding the frequency of ADCPs, for the water depth up to 70m, a 600kHz ADCP is good. For depths up to 110m, it would be more appropriate to use a 300kHz ADCP. And for deeper waters, which might be found near Incheon, areas with a depth of more than 1000m should use a 75kHz ADCP.

There are well - known ADCP 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.