How do we measure the coastal currents of Bacolod?

1. Location of Bacolod

Bacolod City forms part of the province of Negros Occidental in the Philippines. It lies on the northwestern coastline of the island of Negros.

Geographically, it faces the Guimaras Strait separating the islands of Negros and Guimaras. The shore area fronting this strait has some sandy beaches and mangrove forests in some parts. It is encircled by very diverse marine waters in the Guimaras Strait. In some places, the strait is quite shallow and hosts a different array of marine life, such as fish, crustaceans, and shellfish. Another reason which adds to the richness of the marine environment is the existence of coral reefs.

On to human activities, Bacolod is a metropolitan city with all kinds of activities, inclusive of a very dynamic economy. The surrounding areas have been known for their sugarcane plantations, which have taken center stage in the local economy. Tourism-wise, this is an expanding industry here, complemented by the fact that there are coasts, adding to the tourist attractions, especially during the MassKara Festival. Fishermen have steady livelihoods through fishing along the coast.

2. How are the coastal currents off Bacolod?

A number of factors influence the currents along the coast of Bacolod. Among major influences on the currents, one is caused by tides. The tides rise and lower due to gravitational pull by the moon and the sun. The rise and fall create the tidal currents. The tidal currents may flow hard and in one direction or be weak and in another, depending on the lunar cycle and also the local topography of the coastline and seabed in the Guimaras Strait.

Of course, the role of the monsoon winds is quite important here. In the Philippines, there are two monsoon seasons. During the southwest monsoon-what Filipinos call Habagat-the winds are from the southwest, and the surface waters are pushed, creating a current in a general flow. On the other hand, during the northeast monsoon, which is called Amihan in Filipino, the winds are from the northeast and a different flow pattern arises.

The topography of the seabed in the Guimaras Strait off Bacolod further affects the coastal currents. Submarine ridges, shoals, and channels might accelerate, decelerate, or shift the direction of currents. This shape of the coastline, in particular bays and headlands, will affect the flow of the currents. Inflow of fresh water from local rivers can modify the density of coastal waters and influence current patterns.

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

The coastal currents of Bacolod have some characteristics on its velocity and flow rate. Velocity may range from relatively slow in some sheltered bays and lagoons to fairly fast in areas where the currents are constricted or subject to stronger winds or tides. The flow rate depends on the volume of water that flows through a given area per unit time.

For valid measurement of such currents, however advanced and convenient methods are needed. One of the highly useful techniques in this regard is the use of Acoustic Doppler Current Profiler(ADCP). The ADCPs are capable of delivering discretized as well as continuous data about the water flow at different depth levels.

3.1 Working of ADCPs operating on the principle of Doppler

ADCP current meter work on the principle of the Doppler effect. They emit acoustic signals into the water. These acoustic waves reflected from moving particles through water, including sediment grains and small organisms, have changed frequency because of their interaction. This shift in frequency is proportional to the velocity of those moving particles and, in effect, the velocity of the water.

With an ADCP current profiler sending out many sound beams at different angles, it can measure the three-dimensional velocity of the water. It's able not only to evaluate the horizontal velocity but also the vertical components of the velocity, which allows a holistic view of the structure of the flow of water. After processing and analysis, the collected data then gives correct information on the current off the coast.

3.2 What is required to perform a high - quality measurement of Bacolod coastal currents?

High - quality measurement of the coastal currents near Bacolod requires consideration of many factors, related to equipment. First of all, material reliability for the device to be able to resist such a very aggressive marine environment means the impact of saltwater, high humidity, and pressure changes.

The size and weight of the equipment, as well as its power consumption, also have to be taken into consideration. A smaller size and lighter weight make it easier to deploy and handle, especially in situations when the measurement needs to be done from a small boat or floating platform. In addition, low power consumption is critical for the equipment to operate over a prolonged duration without the need for frequent battery replacements or external power supplies.

Another important factor is cost. In order to enable large-scale measurements, the equipment has to be moderately expensive. Among the highly suitable materials for casing ADCP doppler is the alloy of titanium. The alloy of titanium has several advantages. It is very strong and durable and also resists the corrosive action of saltwater. In addition, its density is relatively low, which can keep the overall weight of the device down. It also has excellent thermal properties, which should help with the extreme temperature conditions of the marine environment.

3.3 How to Choose the right equipment for current measurement?

Regarding the choice of appropriate equipment to measure the currents along the coasts of Bacolod, various considerations should come into play. First among them is the mode of deployment. Depending on how they are deployed, there are several types of ADCP flow meter.

If the measurements are to be performed from a ship, then only a ship-borne ADCP would be needed. It can be fixed on the hull of the vessel and perform continuous measurement as the ship moves through water.

If the measurement is to be done from the seabed, then a bottom-mounted ADCP meter may be used. In this case, the ADCP is directly placed on the seabed and measures the currents passing above it.

Where there is to be a floating platform, then a buoy-mounted ADCP would be very appropriate. It can be fixed underneath a buoy and measure currents of the surrounding water.

Besides the deployment mode, the frequency of the ADCP profiler also needs to be chosen depending on the depth of the water. Considering that the water depth is up to 70 meters, 600 kHz ADCP normally turns out to be a good choice as it would provide high-resolution measurements. For water depths ranging between 70 to 110 meters, a 300 kHz ADCP will be more appropriate. For deeper waters, at depths up to 1000 meters, a 75 kHz is recommended in order to measure the currents correctly because it can penetrate deeper into the water.

There are some well-known brands for ADCP in the market, such as Teledyne RDI, Nortek, and Sontek. However, China Sonar PandaADCP may be a good option for customers with excellent quality and cost-effectiveness. It is all-titanium-alloy material, ensuring that in the marine environment, the product will be durable and not compromised in functionality. Moreover, the cost-performance is comparatively amazing. More about it is available on its official website: https://china-sonar.com/.

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