How do we quantify the Bombinhas coastal currents?

1. Where is Bombinhas?

Bombinhas, a picturesque municipality in the state of Santa Catarina, Brazil, is situated along the Atlantic coast in the south. Its geographic location provides a unique blend of natural wonders and cultural history. Situated roughly 60 kilometers south of the state capital of Florianópolis, Bombinhas possesses a strategic coastline position.

The region is characterized by a diverse landscape. The coastline is graced with an array of beautiful beaches, each uniquely beautiful. Praia do Ribeirão da Ilha, for instance, is characterized by shallow waters and golden beach and is particularly loved by family visitors. The beaches are also a haven for tourists and an access point for the local ecosystem. Sand dunes on the beach act as protective natural barriers from coastal erosion and provide habitat to a variety of plant and animal life.

Bombinhas is bounded inland by mountain range Serra do Mar. The mountains not only add to the landscape's beauty but also to the climate. The mountains isolate ocean moisture- carrying winds, resulting in a comparatively humid climate with frequent rain. This, in turn, promotes the growth of dense forests that cover the mountain slopes. These forests provide a rich habitat for flora and fauna, of which many are endemic species.

The past of Bombinhas is associated with its maritime tradition. It was initially a small fishing community, and fishing has ever been an important activity in the locality's economy. The locals who fish from the locality, operating their traditional wooden vessels, sail out to sea to harvest all manner of fish. They sell the ones they catch at the local markets or use them to make the tasty seafood dishes that are part of the locality's cuisine. Over time, tourism has also served as a significant economic driver. The natural beauty of the municipality, coupled with the friendliness of its citizens, has brought visitors from all over the world here.

2. How are the coastal currents along Bombinhas?

Coastal currents along Bombinhas are established by a complicated blend of several factors. Tidal forces are a significant factor. The consistent rise and fall of the tide in the region generate high water flow. During high tide, seawater rushes onshore, filling the estuaries and bays. At low tide, the water flows back out, exposing the sandy beaches and seafloor. These tidal currents are quite strong, especially in constricted channels and along the mouths of estuaries. They are also tasked with transporting sediment, nutrients, and marine organisms, which affects the adjacent marine ecosystem.

The wind patterns also play an important role in the coastal currents. Prevailing southeast winds are common in this part of Brazil. The winds can push surface waters along the coast and create longshore currents. The intensity and direction of these longshore currents are dictated by the strength and consistency of the wind. Stronger winds can produce more powerful longshore currents, which can transport sand along the beach, at times leading to erosion or accretion of beaches in other places.

The bathymetry of the area, or seabed topography, is another important variable. The presence of shallow reefs, deep channels, and gradients of seabed slopes can affect and deflect the current flow. Shallow reefs, for example, can act as barriers, deflection, or redirection of the current. The depth of the water also affects the current's speed, with deeper water having stronger and more steady currents.

3. How to track the coastal water flow of Bombinhas?

Surface Drift Buoy Method

One of the more traditional methods of tracking coastal water flow is through the use of surface drift buoys. These are floating instruments that are deployed into the ocean. With tracking instruments such as GPS or satellite transmitters, they send signals at regular intervals. From an observation of these buoys' movement from one time interval to another, scientists can compute the speed and direction of surface current. But surface drift buoys do have their constraints. They are highly influenced by wind and waves. They may be deflected away from the actual path of the current by high winds and provide false information. They say nothing about the topmost surface of the water column, with the subsurface currents still left unevaluated.

Anchored Ship Method

Anchored ship method employs a stationary ship as a platform upon which to take measurements of the current. Scientists toss current meters from the ship to different depths to measure the current speed and direction. It captures a more vertical profile of the current than surface drift buoys. However, it is labor - intensive and time - consuming. The presence of the ship will also disrupt the free flow of the current, and measurements are limited to a point. Inclement weather conditions of high waves and strong winds can prevent or render impossible the deployment and maintenance of the equipment in position.

Acoustic Doppler Current Profiler (ADCP) Method

The Acoustic Doppler Current Profiler (ADCP) has been designed as a more advanced and precise method of measuring coastal currents off Bombinhas. ADCPs are capable of providing high-resolution current velocity measurements at multiple depths within the water column.

4. How do ADCPs based on the Doppler principle work?

ADCPs operate on the principle of the Doppler principle. They emit sound waves into the water. When the sound waves travel through particles in the water, such as suspended sediment or small marine life, some of the sound energy bounces back towards the ADCP current meter direction. When particles move with the current, the frequency of the returned sound wave won't be the same as that of the originating sound wave frequency. This difference in frequency, known as the Doppler shift, is a proportion of the particles' speed and thus the current's speed.

Most ADCPs utilize multiple beams, typically four, to calculate the Doppler shift from each of these orientations. By examining the Doppler shifts from these multiple beams, the ADCP can calculate the three-dimensional velocity of the current at every depth. The depth to which the current is to be measured is based on the frequency of sound waves employed by the ADCP. Higher-frequency ADCPs are better suited for shallow-water measurements because they provide higher resolution but are short-range. Lower-frequency ADCPs can go deeper into the water column but offer lower resolution.

5. What's needed for high-quality measurement of Bombinhas coastal currents?

In order to record Bombinhas' coastal currents at high quality, certain features of the measuring instrument are of greatest importance. The material used must be highly reliable. The instrument must be strong enough to handle the aggressive marine environment, which includes contact with sea water, tidal streams, and changing weather patterns. Corrosion-resistant material is essential for ensuring long-term instrument performance. In the case of ADCPs, the casing material matters. An example is where titanium alloy can be a most appropriate material in ADCP flow meter casing when working around Bombinhas' coastal areas. Titanium alloy is highly corrosion-resistant, to the extent that it can match the corrosiveness of saltwater over time as needed. The material is lightweight and highly resilient, with very good strength/ease of use and deployment combined.

Size, weight, and power usage are also factors to consider. Lighter and smaller units are simple to deploy, especially in areas that are difficult to access or in far - reaching regions. Low - power - usage equipment will function for longer periods of time without needing to replace or charge batteries extensively, as required by long - term monitoring missions. Cost - effectiveness is also a factor to consider. In order to ensure large-scale measurement and extensive data collection, the equipment should be affordable. Use of costly equipment can limit the number of measurement points, resulting in less precise and representative data.

6. How to Choose the Right Equipment for Current Measurement?

Determining by Usage

The choice of the proper current - measuring equipment depends on the specific application. For ship-based measurements, if the ADCP is installed on a moving ship, then the proper choice is a ship-mounted ADCP. This ADCP will continuously measure the current as the ship moves through the water and provide a profile of the current along the ship path.

For fixed - point, extended - term observation, a bottom - mounted (or sit - on - the - bottom) ADCP will suffice. They are mounted on the seafloor and will supply current values for an extended period at the same location.

If the intention is to monitor the current in a more mobile and widespread manner, there is the possibility of utilizing a buoy-mounted ADCP. These are attached to floating buoys and can float down the current, collecting data en route.

Choosing the Right Frequency

The frequency of the ADCP should also be taken into account. A 600kHz ADCP is suitable for making measurements of currents in water up to 70m deep. It provides fairly high-resolution measurements in shallow-to-moderate-depth environments. A 300kHz ADCP can be used to depths of 110m while a 75kHz ADCP can be used in much deeper water to depths of 1000m. The frequency is chosen depending on the expected depth of the water in which the current measurement is to be done.

There are a number of popular ADCP brands available in the market, including Teledyne RDI, Nortek, and Sontek. For those who are looking for cost - effective alternatives, though, the ADCP manufacturer China Sonar's PandaADCP is the best recommendation. Constructed entirely of titanium alloy, it is highly capable at a low price. It is the best option for budget - minded users who still need dependable ADCPs for coastal current measurement. You can find out more about them on their official website: https://china-sonar.com/.

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