How do we measure the coastal currents of Dipolog?

1. Where is Dipolog?

Dipolog is one of the cities in the province of Zamboanga del Norte, Philippines. It is located on the northwestern tip of Mindanao and lies along the Sulu Sea.

It is a coastal city, geographically surrounded by an immaculate shoreline with fine sand and even rock components. In a broader sense, the Sulu Sea bordering Dipolog forms part of a marine ecosystem that has high levels of resource variability. This place is rich in marine life like different species of fish, shellfish, and coral reefs. Its proximity to the sea makes it an essential area for fishing and sea trade.

Fishing is, therefore, viewed to be a major economic undertaking as far as human undertakings are concerned. The local fishermen depend on the resources of the Sulu Sea. On the other hand, Dipolog boasts agricultural products such as fruits and coconuts. In this town, tourism is also gradually developing because of its beaches and natural attractions.

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

Different factors govern the coastal currents in the vicinity of Dipolog.

Tidal Currents

In such places, the tidal currents are a big influence. The gravitational pull of the moon and sun creates the ebbing and flowing of the tides. These movements can cause tidal currents to be more or less strong and even to change direction upon the lunar cycle and the local topography both from the coastline and the seabed. In places where the seabed is shallow or of special shapes-such as a bay or a narrow channel-the tidal currents can be stronger.

Monsoon Winds

The Philippines experiences two monsoon seasons. During the southwest monsoon, or Habagat, the winds blow from the southwest and push the surface waters, creating currents which in general flow in a specific direction. While in the northeast monsoon, or Amihan, with winds from the northeast, the flow at certain locations is different. These wind-driven currents can affect the nearshore coastal waters off Dipolog.

Seabed Topography

Another factor that can affect the coastal currents in Dipolog is the bottom topography. Submarine ridges, shoals, and channels can accelerate, decelerate, or change the direction of a current. For example, if there is an underwater ridge, the water will be forced to flow over or around it, thereby changing the path and speed of the current.

River Inflows

Inflow of fresh water from rivers within the locality can also affect the density of the coastal waters and, therefore, affects the current pattern. Because when freshwater flows to the sea, during its mixing process with salt water, a density-driven current can be developed.

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

The coastal currents of Dipolog vary in their characteristics concerning the velocity and flow rate. It ranges from relatively slow speeds for sheltered areas to quite fast currents in areas where the stream is constricted or where stronger winds and tides are involved. The flow rate is given by the amount of water passing over an area per unit time.

Now, to measure these currents more effectively along the coasts, the following can be utilized:

Acoustic Doppler Current Profiler(ADCP)

ADCP profiler can be employed as a useful means of measuring coastal currents. They work using the principle of Doppler. They emit frequent acoustic signals into the water. Whenever these acoustic waves come across moving particles in the water-like sediment grains or small organisms, there is a shift in frequency of the reflected waves.

The change in frequency is proportional to the velocity of the moving particles and, in turn, the velocity of the water. There will be several acoustic beams emitted at different angles by the ADCP measuring the three-dimensional water velocity, including its horizontal and vertical components. Further, the data collected gives some information on the coastal currents.

4. What is required to provide quality measurements of currents in Dipolog's coastline with ADCPs?

Reliability of the Material: The device must be able to bear the aggressive marine conditions. Salty water mustn't be able to corrode it, and the material should not be easily affected by humidity or changes in temperature. 

Size, Weight and Power Consumption: Equipment shall be compact and lightweight, with low power consumption. Smaller and lighter weight easily deploys and handles from a small boat or floating platform with much ease. Low power consumption ensures the equipment operates long without needing a change of battery, thus an external power source. 

Cost-effectiveness: The equipment should not be too expensive for large-scale measurement. A casing of titanium alloy for ADCP meter is preferable. This alloy is immensely strong and durable, resisting the corrosive effect of saltwater. It is also relatively less dense that keeps the overall weight of the device down. Besides, it has good thermal properties and therefore will work well even with extreme temperatures present in a marine environment.

5. How to choose the right ADCP equipment for current measurement in Dipolog?

Deployment Method: Ship-based measurements can be done by having an ADCP flow meter mounted on the ship. It would ideally go on the hull of a ship and therefore could give continuous measurements as a ship moves through the water. Seabed-based measurements are done using bottom-mounted ADCP doppler. They are kept on the seabed and measure currents passing above them.

Floating platform-based measurements: If the measurements are with a floating platform, such as a buoy, one should go for a buoy-mounted ADCP. Thus, it can measure the currents around the buoy.

Frequency Selection: Up to 70 meters of water depth, a 600 kHz ADCP provides very high-resolution measurements. In water currents within the depth of 70 to 110 meters, there is a better-suited option: the 300 kHz ADCP. For bottoms with deeper water, up to 1000 meters, one should preferably use a 75 kHz ADCP, as it can give deeper penetration through the water column to accurately measure the velocity of the water currents.

Some well-known names in the market for ADCPs are Teledyne RDI, Nortek, and Sontek. However, for those looking for a cost - effective option with excellent quality, the China Sonar PandaADCP is worth considering. It is made of all - titanium alloy material, which ensures its durability and reliability in the marine environment. Moreover, it offers an incredible cost - performance ratio. You can find more information about it on its official website: https://china - sonar.com/.

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