1. Where is Mukah?

Mukah is a coastal town nestled in the state of Sarawak, Malaysia. It is a place that wears a quaint appeal with its idyllic coastal setting.

With the vast South China Sea surrounding it, Mukah boasts a very long and beautiful coastline. The town is famous for fishing activities since the sea waters have so much marine resources. The locals have a very intimate relationship with the sea, and therefore their traditional way of life was deeply related to fishing and seafaring.

The waters off Mukah represent a very extensive range of shallow lagoons and estuaries along the coastline, where fresh water from the rivers mixes with the salt water from the sea, creating very unusual conditions. These areas represent not only their importance to fishing but also a home for a wide range of shellfish, crabs, and juvenile fish. Further offshore, these waters deepen with sandy and muddy seabeds hosting different benthic communities.

The town also boasts of a great cultural diversity. The local communities, the Melanau people included, have peculiar traditions such as the Gawai Festival. This is a display of their rich cultural traditions and the time when the community comes together to give thanks for a bountiful harvest and a prosperous year.

2. What about the situation with the coastal currents near Mukah?

Many factors act upon the coastal currents near Mukah. There is dominance of seasonal monsoon winds. In the period of the southwest monsoon, strong winds push the surface waters, which again give way to a specific direction within which the flow of coastal currents occur. It may also mean the transportation of nutrients and sediments along the coasts. During the northeast monsoon, the pattern of movement of water is different.

The tides themselves have a significant effect on the sea shore current of Mukah. It can have rapid fluctuations in the current speed and flow direction due to its two ebbs and flows each day. At estuaries and lagoons, these tidal currents are particularly strong; accordingly, their effect on marine organisms and sediment distribution varies.

Other factors involve the shape of the coastline and the topography underwater. The headlands and bays may tend to converge or diverge the currents. For example, around a headland, the currents may accelerate, creating areas of strong tidal streams. Ridges and troughs in the topography of the seabed may cause the vertical structure of the currents to be deformed.

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

Surface Drifting Buoy Method: It is the easiest method to observe the surface currents. buoys are deployed in the water and let it drift with the flow. Tracking their movement using satellite-based or other tracking systems we can get information about the direction and speed of the surface current. But it can give data only from the very top layer of the water and may not present a complete picture of the current profile throughout the water column.

Anchored Ship Method: A ship is moored in a certain position, and from it, current-measuring instruments are lowered into the water. These can measure at any depth the speed and direction of the current. However, the ship may interfere with the natural flow of water. This method is thus relatively more labor-intensive and less fitting for continuous long-term recording.

Acoustic Doppler Current Profiler Method: ADCP represents a more sophisticated and practical means of measuring coastal current. It is capable of providing a well-detailed profile of the water current velocities from the surface to a certain depth.

4. How do Doppler principle-based ADCPs work?

Working principles of Acoustic Doppler Current Profiler (ADCP) is basically according to the Doppler effect. They emit into the water acoustic pulses. As these pulses interact with particles in the moving water-such as sediment particles or small organisms-the frequency of the reflected pulses changes. The change in frequency is proportional to the velocity of the water. The ADCP current meter can then calculate the velocity of the water at various depths from this frequency shift. This instrument has multiple transducers that can send and receive acoustic signals in different directions; thus, it is able to measure the three-dimensional velocity structure of the water column.

5. What is needed for good quality measurements of Mukah coastal currents?

This would call for the measuring equipment of the coastal currents near Mukah to be made from materials whose properties ensure high-quality measurement. The device must be resistant to the corrosive action of seawater and mechanical forces resulting from waves and currents. A small size and lightweight are also desirable in order to make its deployment quite easy, either in a boat, buoy, or at the seabed.

This low power consumption is particularly important in making long-term measurements over a wide area; it will allow the equipment to operate with minimal interruption due to battery replacement or a power supply. It must be cost-effective. For carrying out extensive measurements, this equipment must be reasonably affordable.

The casing of the ADCP current profiler shall be made of a Titanium alloy. The corrosion resistance of a titanium alloy is excellent, very important in the sea environment, and it is strong and durable to sustain bad sea conditions with relatively light weight.

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

Usage scenarios include but are not limited to the following: When selecting equipment for current measurement at Mukah, usage is a scenario that must be put into consideration. A ship-mounted ADCP is suitable for measurement while onboard a ship; therefore, it can be mounted on the hull of a ship for the measurement of currents when a ship is either sailing or stationary.

If it is for measuring the currents near the bottom, then a bottom-sitting ADCP should be used. It can be placed on the seabed and provide an accurate measurement over ground currents.

The buoy-mounted ADCP is applicable in floating applications. The ADCP flow meter can be fixed to a buoy and measure currents at varying depths as the buoy floats.

Regarding the frequency of ADCPs, in water with depths up to 70m, a 600kHz ADCP often works quite well. For around up to 110m, a better option would be a 300kHz ADCP, and for those upwards of 1000m, then there is the 75kHz ADCP that gets pretty robust measurements.

There are several well - known ADCP brands such as Teledyne RDI, Nortek, and Sontek. However, the China Sonar PandaADCP is a highly recommended Chinese brand. It is made of all - titanium alloy material, ensuring excellent performance and durability in the marine environment. It also offers an outstanding cost - performance ratio. You can find more information on its website: https://china-sonar.com/.

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