How to measure the coastal currents of Tuy Hòa?

1. Where is it situated?

Tuy Hòa is a city located in Phú Yên Province, Vietnam. It is situated on the central coast of Vietnam and is orientated toward the East Sea. This coastal city is a place of natural beauty and cultural significance.

The landscape of Tuy Hòa is made of sandy beaches combined with small mountains and fertile plains. The city's beaches are a major attraction, with soft sand and clear waters. Fishing, agriculture, and a growing tourism sector form the basis of the economy in the province. Many ethnic groups populate the area, and their rich traditions and cultures make this city special.

The neighboring East Sea is extensive and significant in area. Its coastal waters abound in marine life, such as fish species, shellfish, and seaweed. In fact, this sea plays a vital role in the regime of the regional climate, regulating temperatures, and its process influences weather patterns. There are some small islands not too far from Tuy Hòa that contribute to diversities within the marine ecosystem.

2. What is the situation of the coastal currents near Tuy Hòa?

Various factors prevail that influence the coastal currents around Tuy Hòa. The dominant influence comes from monsoon winds. The northeast monsoon, which blows from November to March, would drive the surface currents southward owing to strong winds. The southwest monsoon from May to September changes the wind direction and, consequently, the flows in a northerly direction.

Tidal current is another important factor. The tides in the East Sea around Tuy Hòa basically depend on the gravitational pull of the moon and the sun. There are semi-diurnal tides, with two high and two low tides every day. Sometimes the tidal currents are very strong, although mostly near river mouths and narrow passages in the coast. These indeed play an important role in sediment and nutrient transport.

The shape of the sea floor and the underwater relief in general, such as ridges and channels, can also modify the coastal currents. Discharge of rivers into the sea may also affect current patterns. Density differences caused by freshwater input from these rivers create different directions of flow in some areas that may result in the formation of complex current systems.

3. How to Observe the Coastal Water Flow of Tuy Hòa?

There are several methods to observe the flow of coastal water in Tuy Hòa.

The Surface Drifting Buoy Method

This is very straightforward and workable. Buoys are turned loose in the water and have GPS or other forms of trackers installed upon them. As the buoys are moved by the currents, after some time, their position can be checked to see the general direction and speed that the surface currents are moving in. The buoys must be designed to resist the local marine conditions concerning wave motions and salinity.

The Anchored Ship Method

A ship is anchored at a particular point, and current-measuring instruments are dropped from the ship. These instruments measure the velocity and direction of the flow of water at a depth. However, this technique suffers from certain drawbacks. The ship could be subjected to waves and wind effects, which may result in inaccurate measurements. It is also rather inefficient in order to cover a large area.

Acoustic Doppler Current Profiler (ADCP) Method

This is a far more sophisticated and effective means of measuring the flow in the coastal water. ADCPs measure the current water velocity profile over a wide range of water depths. They accomplish this by projecting sound waves into the water and interpreting the reflected waves' Doppler shift. In this way, detailed knowledge of the current structure from surface to seabed is derived.

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

ADCPs operate based on the Doppler principle. They emit acoustic pulses, or simply sound waves, into the water. These sound waves interact with particles in the water, including sediment, plankton, and other small particles. When the sound waves bounce off these particles and are reflected back to the ADCP current meter, the frequency of the reflected waves changes due to something called the Doppler effect.

If the particles are moving towards the ADCP, then the frequency of the reflected wave is higher than the original emitted frequency. If the particles are moving away from the ADCP current profiler, the frequency of the reflected wave is lower. By measuring this frequency shift precisely, the velocity of the particle can be calculated by the ADCP flow meter. As the particles are in motion with the water current, the calculated velocity of the particles is a measure of water current velocity.

They can radiate sound pulses in more than one direction; hence, ADCPs are able to measure current velocity in three dimensions and at varied depths. For instance, they can take the velocity of current at vertical profile and along the depth at intervals from the surface to the seabed. They can provide a comprehensive view of the current structure.

5. What's needed for high - quality measurement of Tuy Hòa coastal currents?

The devices also have to be of reliable material to provide high-quality measurements of the currents in the coastal areas of Tuy Hòa. Due to the presence of a salty, corrosive marine environment with possible physical impacts by waves and debris, a casing should be strong enough.

The size of the equipment should be small enough to be easily deployed, especially in areas with limited access, such as in small boats or in shallow coastal waters. The design should also be lightweight for convenience in handling and installation.

Low power consumption is vital for long-term measurements. Cost-effectiveness is also very important for the possibility of large-scale measurements. In the case of ADCPs, the casing is preferably made from titanium alloy. Titanium alloy is first class in corrosion resistance, especially crucial to a marine environment like Tuy Hòa. It can withstand the corrosive effect of salt water over a long period. It is also strong and features a high strength-to-weight ratio, which provides a durable yet light-weight structure that can protect the internal components of the ADCP profiler.

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

The usage is the first consideration in choosing the right equipment for current measurement in Tuy Hòa.

For Measurements from a Moving Vessel

A ship-borne ADCP will do the job. It provides real-time current data while the ship is in motion and can give a broader view of the flow of water at different locations.

For Measurements at a Fixed Location near the Seabed

A bottom-mounted ADCP is ideal. It monitors current continuously at a specific point, giving data with consistency over time.

For Measurements that Should Cover a Wide Area and be not Restricted to a Specific Depth A buoy - type ADCP is suitable. It will be able to cover a larger area without limiting itself to any particular depth.

Regarding the choice of frequency, for water depths up to 70m, a 600kHz ADCP is a good choice. For depths between 70m and 110m, a 300kHz ADCP is more suitable. For very deep waters of up to 1000m, it is recommended to 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 a great cost - performance ratio. You can find more information about it on the website: https://china-sonar.com/.

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