How do we measure coastal currents of San Fernando?

1. Where is San Fernando?

There have been several places that bear the name of San Fernando. For this purpose, let's deal with San Fernando in the Philippines. It is located in the province of La Union.

Geographically, it is a coastal city that faces the South China Sea. The coastline of this city runs in an irregularly contoured line with fine sandy beaches and rocky shores. The city is surrounded by flat areas of coastal plains interwoven by mild hills. The South China Sea bordering San Fernando is part of the wide expanse of water that surrounds a richly complex marine ecosystem.

As far as human activities are concerned, fishing is an important sector in the local economy. Local fishermen avail themselves of the rich marine resources in this area. Tourism has also been on the rise, with beaches attracting both local and international tourists. The city has a unique culture of locals with its festivals and traditions largely revolve around sea and fishing.

2. What is the condition of the coastal currents around San Fernando?

Various factors influence the nature of coastal currents around San Fernando. Indeed, tidal currents have a forefront prominence. The gravitational pull by the moon and the sun causes coming in and going out of the tide, hence the tidal current. The tidal currents vary in strength and direction with respect to the lunar cycle and the local topography of the seabed.

Another important influence would be the monsoon winds. Different monsoon seasons occur in the region. For example, during the southwest monsoon, winds coming from the southwest could be so strong as to push the surface waters and develop currents that flow in a certain direction. Conversely, the winds from the northeast in the northeast monsoon could give rise to different flow patterns.

The form of the coastline and seabed topography are other important factors. The bays, headlands, and submarine ridges could hasten or slow the currents and alter the direction. Inflow of fresh water from nearby rivers or streams can also affect the density of the coastal waters and influence the current patterns.

3. How to observe the coastal water flow of San Fernando?

The coastal currents of San Fernando have their characteristic velocity and flow rate. The range of the velocity may be from slow in the sheltered area up to relatively fast, especially in regions where the currents are constricted or affected by stronger winds or tides. The flow rate shall depend on the volume of water passing through a given area per unit time.

For all such measurements of coastal currents, Acoustic Doppler Current Profilers are quite efficient. ADCP current meter could give very handy and precise data about the flow of water at different depths.

3.1 How do Doppler Principle-based ADCPs work?

Acoustic Doppler Current Profiler (ADCP) work on the principle of the 'Doppler effect'. They transmit acoustic signals into the water. These signals scatter off the moving particles in the water, such as sediment, plankton, and small organisms. When the acoustic waves are reflected back by these moving particles, their frequency changes.

The frequency shift is directly proportional to the velocity of the moving particles, which is itself proportional to the water velocity. Where ADCP current profiler transmit several acoustic beams from different directions, one can measure the three-dimensional velocity of the water, including its horizontal and vertical components. Data is then processed for practical information about the coastal currents.

3.2 What's required for high-quality measurement of the San Fernando coastal currents?

In order for good, quality measurements of the coastal currents around San Fernando to be made, the equipment in question needs to meet certain conditions. The construction material for such equipment should be reliable enough to deal with the harshness of the marine environment. It needs to be sufficiently resistant to the corrosion effects of saltwater and from the effects of humidity and temperature fluctuation.

The instrument shall be compact, light of weight with minimum power consumption, and be reasonably inexpensive in order to make large-scale measurements feasible. A casing of the ADCP doppler made from a titanium alloy is preferred. Excellent resistance to corrosion is exhibited by the alloy of titanium that is important in a salt-water environment; it is also strong and durable, capable of resisting the mechanical stresses of the marine environment. Its relatively low density helps to minimize the weight of equipment, and it has good thermal stability, useful in the variable temperature conditions of the sea.

3.3 How to choose the right equipment for current measurement?

While choosing the equipment to measure current at San Fernando, the deployment method needs to be considered. There are different types of ADCP flow meter for different applications.

For ship-based measurements, an ADCP meter mounted on a ship would be apt. It measures the current as the ship travels through the water.

If the measurement is to be done from the seabed, then it requires an ADCP mounted on the bottom. It simply would sit on the seabed and measure the currents passing above it.

For measurements using a floating platform, like those by a buoy, a buoy-mounted ADCP is exactly what one needs. It measures the currents around the buoy.

For doing so, in water as deep as 70m, a frequency of 600kHz gives high-resolution measurements. In water between 70-110 meters deep, the desirable class is 300kHz, while in deeper waters of up to 1000m, the desirable class is 75kHz because it will give a greater depth of penetration, hence more accurate results of the currents.

Among the ADCP profiler brands, well - known ones include Teledyne RDI, Nortek, and Sontek. However, for a cost - effective option with excellent quality, the China Sonar ​PandaADCP is a good choice. It is made of all - titanium alloy and offers an excellent price - performance ratio. You can visit ​https://china-​sonar.com/ for more details.

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