How can we measure the Coastal Currents of Terengganu?

1. Where is Terengganu?

Terengganu is a state in Malaysia and lies on the east coast of the Malay Peninsula. The South China Sea, which carves much of its coast, bounds it to the north. The state is a cascade of beautiful beaches, clear blue waters, and a laid-back coastal lifestyle.

The capital, Kuala Terengganu, is a lively center: modern infrastructure combined with traditional Malay architecture. Locals are predominantly Malays, and their rich cultural heritage is reflected in several historical mosques, handicrafts, and traditional festivals.

The South China Sea one sideways of Terengganu is immense and dynamic. Extensive coral reefs occur in the coastal areas and support a variety of marine life, from colorful fishes and sea turtles to different kinds of invertebrates. Beaches, like those in the Redang Island and Perhentian Islands, attract tourists. Its sea provides food via fishing and shipping. Mangrove forests line segments of the coast, which also acts as a natural barrier to erosion and habitats for many species.

2. What is the condition of the coastal currents off Terengganu?

Several factors in general govern the coastal currents off Terengganu. First, there are the monsoon winds. Strong winds of the northeast monsoon between November and March can drive the surface currents in a southerly direction. During this period, rough seas with higher wave energy occur. In the southwest monsoon, which lasts from May to September, its effect is different in most cases, and in fact, it alters the direction of flow to become northerly.

Tidal currents also play a huge role. The tides in the South China Sea along Terengganu, as explained by many scholars, are induced by the gravitational pull of the moon and the sun. The area has semi-diurnal tides, with two high tides and two low tides each day. The tidal currents could become very strong, particularly around river mouths and narrow constrictions in the coastal areas. These currents play a very important role in the distribution of sediments and nutrients along the coast.

The local bathymetry, through the shape of the seabed and occurrence of underwater features like ridges and channels, can modify the coastal currents. Discharge of rivers into the sea, like the Terengganu River, also has the potential for modifying current patterns. This inflow of fresh water can set up various density differences that may lead to a complex system of currents.

3. How to observe the water flow at the coast of Terengganu?

For observing the Terengganu coastal water flow, several methods are available. A common and practical method is the surface drifting buoy technique. Buoys are released into the water, each fitted with GPS or any other tracker device. Moving in the water, buoys are carried out by the currents, where their position and movement over time can be monitored to determine the direction and speed of the surface currents.

It consists of anchoring a vessel at one position and measuring the current flow of water at different levels using current-measuring devices. The drawback with this, however, is that the ship may be tossed about by waves and winds that may put into question accurate measurements obtained from such. It is also not quite efficient in covering a large area.

In contrast to the normal method, the ADCP method is more improved and effective in measuring water flow at the coast. The ADCP current meter also have a basis on the principle of measuring the velocity profile of water currents at a wide range of depth. They basically operate by emitting sound waves into the water and analyzing the Doppler shift of the reflected waves. This gives a very detailed understanding of the current structure right from the surface down to the seabed.

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

The Acoustic Doppler Current Profiler (ADCP) work on the principle of the Doppler effect. They send out acoustic pulses, or in other words, sound waves, into the water. Particles in the water like sediment, plankton, and other small particles scatter these sound waves. When these sound waves reflect back through a collision with these particles to the ADCP flow meter, under the influence of the Doppler effect, the frequency of the reflected waves shifts.

In case the particles move towards the ADCP current profiler, then the frequency of the wave reflected is higher than the originally emitted one. If the particles are moving away from the ADCP, then the frequency of the reflected wave is lower. This frequency shift is measured very precisely and, using this, the ADCP calculates the velocity of the particles. Since the particles are moving with the flow of water, the velocity calculated for the particles is a measure of the velocity of the water current.

They have the ability to emit sound pulses in all directions and, therefore, can measure current velocity in three dimensions and at many depths. For example, it measures current velocities in a vertical profile every interval from the surface down to the seabed and thus provides an overview of the structure of the current. The other way is by vertically profiling the bottom-mounted ADCPs.

5. What is needed to accomplish high - quality measurement of Terengganu coastal currents?

The equipment is needed to be made from reliable materials, for high-quality measurement of the Terengganu coastal currents. Since the marine environment is so unfriendly because of saltwater corrosion and potential physical impacts due to waves and debris, it requires a casing that is strong.

They must be designed with the smallest size to carry or deploy easily into particular areas which are difficult to access, for example, some little boats or shallow waters in areas along coastlines. In addition, lightweight designs are preferable for maneuvering and installation feasibility.

Low power consumption is one very important factor taken into consideration because these are for long-term measurements. Cost-effectiveness is also an important contribution to large-scale measurements. In the case of ADCP profiler, the casing is preferably made of titanium alloy. Excellent corrosion resistance is essential for the marine environment in Terengganu. It can stand against the corrosive effects of saltwater for a very long period. Additionally, it is strong enough and contains a very high strength-to-weight ratio; hence, the structure will be durable and lightweight to protect the internal components of the ADCP meter.

6. Selection Criteria of Appropriate Equipment for Current Measurement

As far as the selection of proper equipment for current measurement in Terengganu is concerned, usage becomes the first consideration. A ship-borne ADCP will be quite handy for measurements from a moving vessel. Besides providing real-time current data, it can also represent the ship while in motion.

The ADCP mounted from the bottom will be good for a fixed location measurement near the seabed. It can monitor continuously the current of a certain point.

For measurements that need to cover an extensive area, not restricted to a specific depth, it is appropriate for an ADCP of a buoy type.

As for the choice of frequency, the ideal frequency in waters as deep as 70m is 600kHz, while a 300kHz ADCP should be used within the range of 70-110m depth. For very deep waters, as far down as 1000m, a 75kHz ADCP is recommended for measurement.

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.