How to measure the Mawlamyine Coastal Currents?

1. Where is Mawlamyine?

Mawlamyine is a city in Myanmar and is located within the Mon State. It is situated on the eastern shore of the Gulf of Martaban. It is a city that has been famous for its historical, cultural values, and combines nature and man-made structure in the most beautiful way.

The environs of Mawlamyine consist of a plain that tapers down gently to the coastline. The town is pregnant with old pagodas, colonial-era buildings, and a vibrant local market. People in Mawlamyine engage in all types of work, but because of its position along a coastline, fishing and trading prevail.

The Gulf of Martaban is a large body of water with various ecological life. Nutrient-rich coastal waters host an immense variety of marine life. The mangrove forests also verge parts of the coasts, acting as a natural barrier against erosion, which again creates a home for several species such as crabs, shrimps, and different kinds of fish. Several rivers pour into this gulf and account for its special hydrological conditions.

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

These various factors mould the coastal currents around Mawlamyine. The tidal currents are dominating. The semiclosed nature of the Gulf of Martaban makes the tides very prominent in their influence on water movements. The ebb and flow of the tides result in the development of intricate current patterns that fluctuate both in speed and direction.

The discharges in the river into the gulf also act upon the currents in the coast. These carried freshwater and sediment in rivers could change the density and salinity of the coastal waters, thus influencing current flow. The wind pattern, most especially during the monsoon seasons, may drive surface currents. The shape of the coastline and underwater topography, including the presence of shoals and channels, could create divergence, convergence, or eddies in currents.

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

Surface Drifting Buoy Method: A surface - drifting buoy can be observed in water to observe the surface current. Further, the movement of a buoy is tracked through GPS or other tracking systems. This method also suffers from certain limitations. It provides information on the surface current only and is affected by wind and wave actions. For example, if the wind is blowing strongly in a different direction from the current, the buoy's path may not accurately represent the actual current direction.

Anchor - Boat Method: An anchored boat can measure the current. In this technique, instruments are lowered from an anchored boat into the water to ensure that the measurement of current at different depths is taken correctly. But, again, there are disadvantages, the area of measurement is limited because of the fixed position of the boat and cannot cover the whole variability of the currents in a large coastal area.

ADCP Method: The measurement of coastal currents can be done in a more advanced and efficient way using ADCP current meter. It projects acoustic signals into the water, measures the Doppler shift of the reflected signals, and ultimately calculates the various depths with the velocity of the water. This provides a much better profile of the current from the surface to the seabed. ADCPs are less affected by surface disturbances and can operate continuously for long periods.

4. How do ADCPs using the Doppler principle operate?

ADCPs work on the basis of the Doppler effect. They emit acoustic pulses into the water. When these pulses interact with moving water particles, the frequency of the reflected pulses changes. If the water particles are moving towards the ADCP profiler, the frequency of the reflected signal is higher than the emitted signal, and if they are moving away, it is lower.

Accordingly, the ADCP meter hosts multiple transducers that transmit and receive signals at different angles. This device calculates the three-dimensional velocity of the water by analyzing the Doppler shifts from different directions and at different depths. This means it can determine the horizontal and vertical components of the velocity, providing a detailed understanding of the current's structure and behavior.

5. What is required to measure Mawlamyine coastal currents of high quality?

High-quality measurement of the coastal currents near Mawlamyine involves the use of equipment that is made from reliable materials, as the marine environment is harsh with saltwater, high humidity, and even storms. Thus, casings should be durable and as small as possible to make deployment and retrieval easier, especially in coastal areas with complex features.

A lightweight design is preferred since it makes the equipment more manageable during installation and maintenance. Low power consumption will be decisive for long-term and autonomous operation. Cost-effectiveness is another important factor that enables large-scale measurements.

The casing of ADCPs is preferably made from titanium alloy. The reasons include corrosion resistance, which is essential to withstand the corrosive seawater effects; its strength to bear up the water pressure at varied depths, and lightness of the nature that makes it more convenient for various deployment methods.

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

Equipment selection for current measurement near Mawlamyine should be considered based on the purpose of use. If it is being used for a vessel's navigation or short-term research, then a ship-mounted ADCP flow meter will be sufficient. It will provide real time current information throughout the voyage.

For measurements near the seabed, such as for studying sediment transport or benthic ecology, a bottom-mounted ADCP current profiler is preferable. It can capture the details of the near-bottom current. If it is necessary to monitor the coastal current for long and wide areas, a buoy-type ADCP will be ideal.

In the case of ADCPs, a 600kHz ADCP is a good selection for the water depths up to 70m, a 300kHz for a depth of up to 110m, and for deeper waters that may be found near Mawlamyine, areas of more than 1000m in depth, a 75kHz ADCP can be 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.