How can we measure the Coastal Currents of Takaoka?

1. Where is Takaoka?

Takaoka is a city in Toyama Prefecture on the Sea of Japan side of Honshu. It's a coastal city that benefits from the resources and transportation opportunities provided by the sea.

The local economy is very diverse, with much of it connected to fishing and manufacturing. The Sea of Japan off Takaoka is rich in marine life such as cod, squid, and various shellfish. There are also large seaweed beds that support the fishing industry.

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

The coastal currents near Takaoka are influenced by more than one factor. To begin with, there is the influence of the Tsushima Current. This warm current, which branches from the Kuroshio Current farther south, carries warm water and nutrients that impact the temperature and the distribution of marine life over the area.

Significant also are tidal currents. The tidal range is substantial in the Sea of Japan, and due to these continuous tides, there are developments of intricate current patterns. In this aspect, the shape of the coastline and the underwater topography are crucial. Various bays, headlands, and underwater ridges make the currents change direction and speed. Besides, the wind patterns, especially the seasonal winds blowing across the Sea of Japan, can drive surface currents and mix different layers of water.

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

Surface Drifting Buoy Method

A surface current could be observed by releasing into the water a drifting buoy. The movement of the buoy over time can be mapped by GPS or other tracking systems. However, this method does have its drawbacks. It gives information only about the surface current and is subject to wind and waves. For instance, if a strong wind blows the buoy in some other direction than the direction the current is flowing, it will result in incorrect measurement of direction and speed of the current.

Anchor - Boat Method

This 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 permits depth-wise measurements in greater detail, there is also a flip side. The fixed position of the boat restricts the area of measurement, and the variability of the currents over a large coastal area might not be captured by the measurement.

ADCP Method Acoustic Doppler Current Profilers are advanced, modern means that measure coastal currents with efficiency. An ADCP profiler sends the acoustic signals into the water, and measures the Doppler shift of the reflected signals to determine how fast the water is moving at various levels of depth.

This gives a better profile of the current 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. As these pulses interact with moving water particles, the frequency of the reflected pulses is changed. If the water particles are moving towards the Acoustic Doppler Current Profiler (ADCP), the frequency of the reflected signal is higher than the emitted one; if they are moving away, it is lower.

Accordingly, the ADCP current profiler has several transducers that send and receive signals at different angles. From the analysis of Doppler shifts in various directions and depths, the device can compute the three-dimensional velocity of the water, hence determining the horizontal and vertical components of the velocity. This gives great detail in understanding the structure and behavior of the current.

5. What is necessary for good-quality measurement of Takaoka coastal currents?

The equipment must be made of reliable materials for high-quality measurement of the coastal currents around Takaoka. A casing that is durable, considering the saltwater, possible exposure to storms, and the influence of tides and ocean currents, would be important. The size of the equipment should be small for easy deployment and retrieval, considering the complex coastal landscape with its bays and headlands.

A lightweight design is preferable because it makes the equipment more manageable during installation and maintenance. Low power consumption is essential for long-term and autonomous operation. Cost-effectiveness is also important to make large-scale measurements feasible.

The casing of ADCPs is preferably made of titanium alloy. Titanium alloy has excellent corrosion resistance, which is vital for withstanding the corrosive effects of seawater. Besides, it is strong and durable to bear the pressure of 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?

When choosing the equipment for the measurement of currents near Takaoka, consider the purpose of the use. In the case of navigation by a vessel or short-term research, the ADCP flow meter installed on the ship would be sufficient to get real current information in real time 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 the ADCPs, for depths up to 70m, a good choice is a 600kHz ADCP. Power consumption increases with depth. For depths up to 110m, a 300kHz ADCP is better. And for deeper water, which may be near Takaoka, with an area depth over 1000m, a 75kHz ADCP is recommended.

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.