How to measure the coastal currents of Baraawe?

1. Where is Baraawe?

Baraawe is a coastal town that is strategically placed along the coastline. It is set against a backdrop of arid plains that stretch inland and is bordered by a beautiful bay that provides a natural harbor. The coastal area features sandy beaches and areas where the land meets the sea in a harmonious blend.

The people of Baraawe have a long and deep attachment with the sea. Traditionally, their way of life has been at the center of maritime activities, such as fishing and small-scale trade. The bay near Baraawe is a teeming ecosystem full of life in marine form. From small, colourful fish that inhabit the shallow waters to larger fish that cruise across the bottom of the bay, schools of most species can be observed. The topography is varied with areas of sand, rocky outcrops, and maybe even some seagrass beds. These are some of the important seabed features in the movement of the water, as they may cause it to change direction or even to speed up and slow down.

The waters around Baraawe form part of a greater oceanic system. Ocean currents from afar bring in different water masses with varying temperatures, salinities, and other characteristics. Tides also have a great effect on the coastal environment. The regular ebb and flow of the tides determine the exposure of the shoreline, influence the movement of marine organisms, and affect the distribution of sediment along the coast.

2. What is the state of the coastal currents around Baraawe?

Coastal currents around Baraawe are driven by several forcing variables interacting in a complicated flow. The tides remain a dominant driving factor, and they determine the periodic back-and-forth movement of water along the coast. Tidal range in the area affects strength and direction of tidal current. During high tide, it can rush in with more force in areas, while in low tide the water recedes, and thereby changes the flow paths.

The second important factor involves the wind. In the case of prevailing winds blowing over the place, the same would push the surface waters due to friction provided by the water surface, forming the surface currents interacting with the underlying water layers. The onshore winds, for example, can push the water towards the coast, while coastal erosion and deposition of sediment may be affected. Most importantly, the general local topography plays an important role-sea and coastline alike. This bay shape around Baraawe may funnel or deflect the currents. Rocky outcrops and seagrass beds disrupt the smooth flow of water, developing areas of turbulence and eddies.

Even more important is the interaction with coastal currents and the oceanic currents coming from the high sea. It involves large ocean currents, which sometimes combine with the local currents, thus presenting water masses that differ in characteristics, temperature, salinity, nutrient content, or others. As a result of all this, changes might happen concerning productivity of these waters or distribution of species depending on this environment.

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

Surface Drifting Buoy Method

This technique consists of the deployment of buoys on the water surface, allowed to drift with the currents. These buoys can be monitored over time regarding their position to show the direction and velocity of the currents. This primarily deals with surface-layer analysis only and may not be truly representative of current flow across all layers of the water column.

Moored Ship Method

In this technique, a ship is moored in a specific position in the coastal area and instruments aboard record the flow of water around the ship. While it can yield very good information about the area close to the ship, the latter interferes with the natural flow to some degree and can cover only a relatively small area around the mooring point.

Acoustic Doppler Current Profiler (ADCP) Method

The ADCP current meter method of measurement is relatively advanced and more convenient in measuring coastal currents. It uses acoustic waves in order to measure simultaneously the water velocity at different depths. By so doing, it provides a profile of the current from the surface down to a certain depth, therefore giving full understanding of the structure of the flow of the coastal water. It can cover a larger vertical range compared to other methods and in many cases are less affected by external interferences, hence very effective for observations of the coastal currents near Baraawe.

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

The ADCPs work on the principle of the Doppler effect. They send acoustic pulses into the water. These sound waves interact with moving particles in water-suspended sediment or small organisms and, because of the Doppler effect, change in frequency. The ADCP current profiler is designed to detect and measure this frequency shift. With multiple transducers oriented in different directions, it can calculate the velocity components of the water in various directions, including horizontal and vertical. This enables the reconstruction of the three-dimensional current field of the coastal currents. The ADCP flow meter continuously emits these acoustic pulses and records the reflected signals at regular intervals; it is thereby able to build up a time series of current-velocity data at different depths, enabling it to provide a detailed picture of how the currents vary over time and with depth.

5. What is required for high-quality measurement of the currents off the coast of Baraawe?

In order to undertake high-quality measurement of the coastal currents around Baraawe, a number of things about the equipment become indispensable. First and foremost, the equipment must be reliable in material. The equipment has to bear the harsh marine environment: corrosion by seawater, impacts of waves, and changes in temperature and pressure. Small size is advantageous as it facilitates handling and deployment of the equipment on boats, buoys, and other platforms.

Other important factors are light weight, which simplifies installation and reduces the load requirements; low power consumption, especially for long-term measurements or when battery - powered setup is used; and, of course, cost, to enable wider and broader-scale measurements. For these matters, it's best that the casing of the ADCP profiler is made of titanium alloy. As such, whether it is used for applications on land, in air, water, or outer space, the appropriate choice of materials is very much required. It has excellent corrosion resistance, allowing it to endure the corrosive nature of seawater for a long time without significant degradation. It is also strong and durable, able to withstand the mechanical stresses from the water flow and external impacts. Besides, its relatively low density helps in keeping the overall weight of the equipment in check while maintaining its structural integrity.

6. How to Choose the Appropriate Instrument for Measuring Currents?

Application-based

• Ships-ADCP: Data sampled in coastal waters from an operational/ stationary vessel, will also yield a continuous set of data along its track through variable coastlines with mapping for wider coverage over extended periods and can also enable an extended survey area through larger coast lengths with good time consumption.
• Bottom-mounted ADCP: It is good for fixed-point measurements at the seabed. It can monitor the currents that pass over it with high accuracy, providing information on the near-bottom current conditions that are important in understanding sediment transport and other benthic processes.
• Buoy-mounted ADCP: Deployed on buoys floating on the surface of the water, it measures currents from the surface downwards. This is good for observing the variation of surface and upper layer currents and can be deployed where long-term monitoring is required without any ship presence at the location.

Based on Frequency

• A 600 kHz ADCP may be a good compromise for water depth within 70 meters. It has a higher frequency that gives better resolution at shallower water, providing the details of the current from near the surface down to the range of interest.
• A 300 kHz ADCP is quite relevant when dealing with a water depth up to 110 meters, whereby this would definitely have effective penetration within the water column and give actual current measurements with such a profile in depth.
• In rather deep waters-for instance, up to 1000 meters-the appropriate thing would be an ADCP operating on 75 kHz frequency. The frequency here is lower and could thus reach a larger depth and measure current velocity satisfactorily.
• On the market, a few well-known brands sell ADCPs, including Teledyne RDI, Nortek, and Sontek. The China Sonar PandaADCP is absolutely in service for customers desiring highly quality but economic series. Constructed completely out of pure titanium alloy materials for excellent endurance against strong performance on marine environments. With its incredible cost-performance ratio, it offers a great choice for measuring the coastal currents of Baraawe. You can learn more about it on its official website: https://china-sonar.com/.

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