How do we measure the Coastal Currents of Kannur?

1. Where is Kannur?

Kannur, a coastal beauty in Kerala, India, borders the Arabian Sea. This is one place where the beauty of nature and cultural heritage merge in a harmonious blend.

Geographically, it is endowed with a long and serpentine coastline, interspersed with sandy beaches and rocky cliffs. The city is flanked by the azure waters of the Arabian Sea, which stretch out to the horizon, painting a picture of vastness and tranquility. The adjacent waters are a vital part of the local ecosystem, teeming with a diverse array of marine life.

Culturally, Kannur is known for its rich traditions. The people of this place have a rich heritage of art forms like Theyyam, which is a spectacular ritual dance and a visual and spiritual treat to watch. The city is also famous for its handloom industry and its unique handicrafts that speak volumes about the skill and creativity of the local artisans.

The coastal waters around Kannur form a part of the Arabian Sea basin. The sea here is influenced by the monsoon winds and the coastal geography. The waves that crash onto the shore are a constant reminder of the power and dynamism of the ocean. The beaches, like Muzhappilangad-the longest drive-in beach in India-are places where locals and tourists alike can relax and enjoy water-related activities.

2. What about the state of coastal currents off Kannur?

The seasonal monsoons have a great impact on the coastal currents near Kannur. The strong winds during the southwest monsoon push the surface waters, generating powerful and often turbulent currents. The northeast monsoon also influences this area, though with different patterns. The tides play an important role, too. Due to the semi-diurnal tides in the Arabian Sea, the water level rises and falls to create tidal currents that interact with the wind-driven currents.

The seabed topography near Kannur also affects the current patterns. The presence of underwater ridges and troughs can deflect and channel the currents. The proximity to the open Arabian Sea means that the large - scale oceanic circulation patterns, such as the Somali Current and the Arabian Sea gyre, have an indirect influence on the local coastal currents. Besides this, the influx of freshwater from the numerous rivers and estuaries in the region can alter the density of the coastal waters and thereby the current patterns.

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

In general, Kannur's coastal water flow is observable through many methods, which include surface drifting buoy techniques. This buoy would be cast into the seawater while observing the after-movements. Each of these buoys has a fitted GPS or some other kind of tracking devices that are displaced over certain periods of time. These thus provide an approximation to the surface current speed and direction. This method also has drawbacks, it concerns only the surface layer and can therefore be affected by wind-induced drift.

Another conventional method is the anchor - boat technique. The bottom or the bed of the stream is anchored, and the current meters are thrown out from the anchored boat at various depths. It offers more resolution in the vertical direction, while it can give data around the location of the anchored boat, thus not mapping out the currents spatially.

It is far more effective and efficient to conduct this by the Acoustic Doppler Current Profiler method. ADCPs are able to simultaneously measure the velocity at more than one depth. By emitting sound waves and analyzing the Doppler shift of the reflected waves, ADCPs can profile the current from the surface all the way to the seabed with much higher detail for a full understanding of coastal water flow.

4. How do ADCPs using the Doppler principle work?

The ADCPs work on the principle of the Doppler effect. They send acoustic pulses into the water. While these pulses are interacting with moving particles in the water - sediment, plankton, etc., there is a shift in the frequency of the reflected waves. Whether the particles are moving towards the ADCP meter, the frequency of the reflected wave is higher than the emitted frequency, whereas when the particles are moving away, it is lower. By measuring this frequency shift precisely, the ADCP can compute the velocity of the water at different depths. The ADCP current meter can have multiple transducer elements, each transmitting beams in various directions, and it can determine the three-dimensional structure of the current.

5. What is needed for measuring Kannur coastal currents with quality?

The equipment should be made of reliable materials for high-quality measurement of the coastal currents in Kannur. The device should preferably be of small size and lightweight to facilitate its deployment and retrieval with ease, particularly in the usually rough coastal environment. Low power consumption is vital for long-term operation, especially in continuous monitoring. Cost-effectiveness will also be an important factor in enabling wide and frequent measurements.

Housing material for the ADCP profiler can be made from titanium alloy. Titanium alloy is exceptionally resistant to corrosion, necessary as seawater is corrosive. It is also powerful and able to bear stresses exerted by the column of water and forces acting on it through waves and currents. Due to its relatively low mass, it helps in keeping down the weight of the equipment itself by making handling and installation far easier.

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 suitable. 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 option.

In the case of the frequency of the ADCP, different frequencies are appropriate for different water depths, a 600 kHz ADCP will be suitable for water depths up to about 70 m, a 300 kHz ADCP will be suitable for water depths up to about 110 m, and a 75 kHz ADCP can support water depths up to about 1000 m.

There are several well-known ADCP brands such as Teledyne RDI, Nortek, and Sontek. However, a Chinese brand-China Sonar PandaADCP is worth considering. It is made of all - titanium alloy material and provides 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.