How to Estimate the Coastal Currents of Johor?

1. Where is Johor?

Johor is a part of Malaysia and is situated at the southernmost tip of the Malay Peninsula. The state of Johor is also flanked to the north by the Straits of Johor while its eastern front faces the South China Sea. Geographically, Johor is a strategic site because it serves as a passage to the neighboring country of Singapore.

It would run from the varied landscapes of the state-from the modern infrastructure and an economy teeming with bustle at Johor Bahru down to the beautiful beaches and coastal areas. In this local setting, one finds a mixture of Malays, Chinese, and Indians in giving birth to a very rich and multicultural society.

Bordering this is the immense, dynamic, and very fluid South China Sea. Coasts of Johor show areas of sandy beaches, which are favorite tourist sites. There are also mangrove forests along coasts, which are very important ecologically. These mangroves serve as natural barriers, protecting the coast from erosion and offering shelter to a great diversity of marine life such as crabs, fish, and birds. Moreover, mangroves are involved in nutrient cycling. It contains in its waters all manner of marine life from colorful corals down to an abundance of fish species.

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

In the case of Johor, several factors are influential in shaping the nature of coastal currents. The monsoon winds are one factor. For instance, the northeast monsoon brings heavy and strong winds, which sometimes arrives between November to March and has enough strength to drive the surface currents southward. The wind flow pattern changes with the southwest monsoon between May and September and generally shifts currents in a northerly direction.

The other factor is tidal current. Tides in the South China Sea off Johor are generated by gravitational pulls of the moon and the sun. Semi-diurnal tides in this area have two high tides and two low tides every day. Tidal currents may be quite strong under these conditions, especially at the mouth of rivers and narrow passages along the coasts. These kinds of currents are important in sediment transport and nutrient distribution.

These currents can also be deflected by the local bathymetry, which is the shape of the seabed, with underwater features such as ridges and channels. Other influences might include discharge into the sea from rivers like the Johor River. Freshwater input from these rivers may lead to density differences and create complex current systems.

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

There are a few methods to observe the flow of water in the Johor coastal area. One of the more common and workable methods is the surface drifting buoy method. Buoys are thrown into the water and fitted with GPS or other tracking devices. While the buoys are being carried by the currents, their position in space and movement over time can be monitored to determine the direction and speed of the surface currents.

The anchored ship method is one in which a ship is kept anchored at a location and some current-measuring instruments record the flow of water at different depths. However, certain limitations are associated with this approach: depending on the waves and winds, the ship is very much liable to get disturbed, hence not correct records, and secondly, it is really inefficient for the coverage of an extensive area.

In this respect, the more advanced and efficient means of monitoring coastal water flow is represented by the method of Acoustic Doppler Current Profiler (ADCP). ADCPs provide current water velocity profiling over large depth ranges. They work by emitting sound waves into the water and analyzing the Doppler shift of the reflected waves. Further, this gives a really good understanding of the structure of currents from the surface to seabed.

4. How do ADCPs using the Doppler principle work?

ADCP current profiler have their basis on the Doppler Principle, which is a well-understood physical phenomenon. ADCPs transmit acoustic pulses into the water, scattering the sound waves off particles in the water, including sediment, plankton, and other small particles. Due to the Doppler effect, when the sound waves are scattered back towards the ADCP, there is a change in frequency.

If the particles are moving towards the ADCP profiler, the reflected wave frequency is higher than the originally emitted one. In contrast, if the particles are moving away from the ADCP flow meter, the frequency of the reflected wave is lower. By precisely measuring this shift in frequency, the ADCP meter can calculate the speed of the particles. Calculated particle velocity can therefore be assumed to be the water current velocity since the particles are displaced by the water current.

They can send pulses of sound in several different directions to obtain current velocity in three-dimensional space and at more varied depths. For instance, they are capable of creating a vertical profile, which in turn allows them to measure the same current velocity on many occasions from the surface to the seabed to provide a more detailed view of the current structure.

5. What is required for good quality measurement of Johor coastal currents?

The materials used should be reliable to ensure high-quality measurement of coastal currents in Johor. Since the marine environment is harsh-with saltwater corrosion and possible physical impacts from waves and debris-casing durability is important.

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. A lightweight design is also advantageous since it can be more efficiently handled and installed.

Low power consumption is important for long - term measurements. Cost-effectiveness is an added advantage to enable extensive measurement work. In the case of ADCPs, the casing is preferably made from a titanium alloy. For the purpose of this study, titanium alloy has excellent corrosion resistance, which is important in the marine environment of Johor. It can resist the corrosive effects of saltwater over time. It is also strong and has a high strength-to-weight ratio to provide a strong and lightweight structure that houses the internal components of the ADCP.

6. How to Choose the Right Equipment for Current Measurement?

Usage is the first consideration when choosing the right equipment for current measurement in Johor. Where the measurements are to be made from a moving vessel, a ship-borne ADCP is suitable. It is capable of providing real-time current data while the ship is in motion.

Bottom-mounted ADCP is a good option for measurement at a fixed location and near the seabed. The other advantages are it can continuously monitor the current at a particular point.

A buoy-type ADCP is appropriate in cases where the area of measurement needs to be large and is not restricted to a particular depth.

Selection of Frequency For water depths up to 70m, a 600kHz ADCP is the right fit. For depths between 70m and 110m, a 300kHz ADCP suits best. Very deep waters, up to 1000m, would warrant using 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.