How can we measure the Coastal Currents of Tirur?

1. Where is Tirur?

Tirur is a town in Malappuram district in Kerala, India. Geographically, it is in the southwestern part of India, bordering the Arabian Sea. Again, this place belongs to a naturally well-off, geo-ecologically important, and diverse part of the earth.

The town is verdant with greenery all around, and agriculture has been an important source for the inhabitants. The local economy is supported by a combination of farming and fishing activities. The people of Tirur have a unique cultural identity that is deeply intertwined with the land and the sea. The adjacent Arabian Sea is a vast and dynamic body of water. The coastline near Tirur is characterized by sandy beaches and estuaries. These estuaries serve as an important part of the local ecosystem, being a site for breeding of different species of fish and other marine organisms.

The sea is an important part of the identity of the town. The waves crashing on the shore create a rhythmic symphony that is a constant backdrop to the lives of the locals. The climate of Tirur is also influenced by the sea, with the sea breezes moderating the temperature and humidity levels. The area is known for its vibrant festivals and traditions that often have a connection to the sea and the agricultural cycle.

2. What is the condition of the coastal currents in the vicinity of Tirur?

A number of factors control the coastal currents in the vicinity of Tirur. The monsoon winds form a major influence. During the southwest monsoon, strong winds blow and drive the surface currents. These wind-driven currents have the potential to affect the distribution of nutrients and sediments along the coast.

Tidal forces, too, are important. Semi-diurnal tides occur in the Arabian Sea off Tirur. The tides accordingly cause tidal currents that, together with the wind - driven currents, interact. Seabed topography near Tirur is another factor affecting current patterns. The underwater topography, like sandbars and channels, may deflect and modify the currents.

This is also dependent on the inflow of fresh water from the rivers and streams that fall into the sea nearby. The density difference between the fresh water and the salt water of the sea may also lead to complex current patterns. Moreover, the larger-scale oceanic circulation in the Arabian Sea may indirectly affect the local coastal currents.

3. How to Observe the Coastal Water Flow of Tirur?

The different ways in which coastal water flow could be observed in Tirur include, but are not limited to, a surface drifting buoy. In the surface drifting buoy method, a buoy is sent into the water and followed for some time. The buoy position could then be found by means of GPS or other location devices. Observing the displacement of the buoy estimates the speed and direction of the current in the surface water. However, this is a surface-layer-limited approach, and the movement of the buoy can be affected by factors such as wind and waves.

The other approach is the anchor-boat method. A boat is anchored at a location, and current meters are deployed from the boat to measure the current at different depths. This technique offers higher resolution of the current profile at a given point, but is confined to the vicinity of the anchored boat and might not be able to catch the full spatial variability of the currents.

The ADCP current meter technique is the more advanced and efficient technique of measurement of coastal water flow. ADCPs are able to measure simultaneously the velocity at more depths. They operate based on emitting sound waves and analyzing the Doppler shift in the reflected waves, whereby the current profile from the surface down to the seabed is obtained comprehensively.

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

The basic operation of an ADCP current profiler is based on the Doppler effect. It sends acoustic pulses into the water. These pulses interact with moving particles in the water-sediment, plankton, and other small organisms. When the particles are moving towards the ADCP meter, the frequency of the reflected wave is higher than the emitted frequency. Conversely, when the particles are moving away from the ADCP, the frequency of the reflected wave is lower. By measuring this frequency shift, the ADCP profiler calculates the velocity of the water at different depths.

Most ADCPs have many transducer elements, which transmit beams in various directions. This permits the device to measure three-dimensional current structure. By using these beam measurements in concert, one is able to produce a much better model of the current than with only a single beam measurement.

5. What is needed to get high-quality measurements of currents in Tirur Coastal Areas?

High-quality measurement of the coastal currents in Tirur needs certain characteristics, the reliability of the materials used for the equipment in order to survive the harsh marine environment, small in size and light in weight to easily deploy and retrieve the device, and low power consumption in order to have long-term operation in a remote or difficult-to-access location.

The ADCP flow meter casing is preferably made from titanium alloy. Titanium alloy has excellent corrosion resistance, which is an important attribute in the corrosive seawater environment. It is strong enough to cope with pressures exerted by the water column and the forces of waves and currents. Its relatively low density helps keep the weight of the equipment low, making it easier during installation and maintenance.

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

The choice of equipment for current measurement depends on the specific application. For ship - based measurements, a ship - mounted ADCP is a suitable option. If the focus is on near - seabed currents, a bottom - mounted ADCP can be considered. For surface and upper - water - column measurements, a buoy - mounted ADCP is a good choice.

Different frequencies are suitable concerning the ADCP frequency and water depth. A 600 kHz ADCP is good for a water depth of approximately 70m, while 300 kHz ADCP is ideal up to about 110m. Also, the 75 kHz ADCP can measure the current at water depth to about 1000m.

There are several well-known ADCP brands such as Teledyne RDI, Nortek, and Sontek. However, a Chinese brand-China Sonar PandaADCP is also a great option. It is made of all - titanium alloy material and offers an excellent cost - performance ratio. You can visit their website at https://china-sonar.com/ for more details.

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