How do we measure coastal currents in Cannes?

1. Location of Cannes

Cannes is a prismatic jewel on the French Riviera, located on the southeastern coast of France. Set within the Alpes - Maritimes department, it has a prime location along the Mediterranean Sea, where the warm embrace of the sun-kissed waters meets the rugged beauty of the nearby hills.

It is the city where the beauty of nature and cultural sophistication go hand in hand. Long a haven for b Markt of international celebrity, lured by its glamorous appeal, the Cannes Film Festival, held annually, is an international gala event where the whole city turns into a stage as the world of films converges with stars, filmmakers, and enthusiasts from all over the earth. It is an event that displays not only the newest in cinema but also contributes to the vivid tapestry of city culture.

The architectural design of Cannes represents an appealing blend of old-world charm and modern elegance. Narrow, cobblestone streets and the ancient buildings in the old town, Le Suquet, give way to sleek, modern structures that line the Promenade de la Croisette. This is the celebrated boulevard fronting the waterfront, with exclusive hotels, expensive boutiques, and rows of palm trees that gently bend to the sea breeze.

The city of Cannes is located right on the Golfe Juan. This gulf makes up a substantial constituent part of the general maritime scenery in this locale. The waters are very clear and usually enjoy a relatively stable temperature throughout the year because of the prevailing Mediterranean climate. It's rich in a variety of sea life. The colorful coral reefs are home to thousands of fish species, while the seagrass meadows have a very important role in water quality and are also used as nurseries for many juvenile marine life. The serenity of the gulf in some areas creates the perfect haven for sailing, yachting, and diving in water activities.

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

These would, therefore, be under the influence of a combination of factors: the general circulation of the Mediterranean Sea, which is in the broad outline; the Mediterranean Sea has a complex thermohaline circulation system caused by disparities in water density because of variations in temperature and salinity. These large-scale currents can, in turn, influence the direction and velocity of the waters around Cannes.

There are also strong effects from local wind patterns. The Mistral is a very strong north-westerly wind that can push surface waters offshore. Displacement in this sense can create upwelling currents, carrying nutrient-rich waters from lower levels to the surface. Nutrients will promote growth among phytoplankton, which will serve as the basis for the marine food chain, thereby impacting the whole ecosystem.

Although the Mediterranean tides are generally less dramatic compared with some other oceans, tidal forces do indeed interact with the coastline of Cannes. The shape of the bays, depth of waters, and undersea features such as ridges all act to modify the tidal impact on currents. This interaction gives rise to complex and sometimes unpredictable current patterns in the area.

3. How to measure the coastal water flow in Cannes?

Surface Drift Buoy

The buoys are sent into the open waters in the surface drift buoy. Afterwards, with tracking devices, preferably GPS receivers on board, these are transported by currents in the waters while the monitoring device records the positions of the buoys at defined intervals. Whereby, the buoy movements have to be analyzed over time by scientists in order to estimate direction and speed of the surface currents. A drawback with this method is that it is limited to giving information about the top layer of the water column, usually only a few meters deep. Besides, the wind is able to drive the buoy movement significantly, displacing them from the real path of the current. This could lead to mistakes if it is not compensated for correctly.

Anchored Ship Method

A ship is kept in one place by the anchored ship method. Current-measuring instruments are lowered at various depths of water from that ship. Those meters would conduct measurements for the speed as well as direction of current where each meter was placed. These meters have mechanical or electromagnetic current meters inside them. It can allow the collection of data on the vertical profile of the current, but this method is confined to the location at which the ship is anchored. Besides that, the presence of the ship could interfere with the natural flow of the water, thereby giving biased measurements, especially in shallow waters.

Acoustic Doppler Current Profiler (ADCP) Method

In recent years, the ADCP current meter technique has become dominant in the field of coastal current measurement. Basically, ADCPs measure the speed of water current velocities at different depths with the use of sound waves. To begin with, they transmit sound waves through the water that bounce off small particles suspended in the water such as plankton, sediment, or even bubbles. These sound waves returned to the ADCP current profiler have frequencies different from the ones initially transmitted. This frequency shift, the Doppler shift, is linearly proportional to the velocity of the particles and hence the water current. An ADCP can present a rather detailed profile of the current from the water surface to the bottom, without the necessity of actual contact at each depth, which makes the method more efficient and less intrusive compared to the two methods described above.

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

The ADCPs work on the principle of Doppler. An ADCP emits a sound wave, which travels through water. While passing through the water, this sound wave reflects off the small particles moving with the water current. The frequency of the reflected wave changes depending on the relative motion of the particles with respect to the ADCP.

Most ADCPs are multibeam, with four or more beams operating at slightly different angles. Because the Doppler shift in each of these beams is proportional to velocity along that beam's axis, the ADCP flow meter can solve directly for the three-dimensional components of water current velocity-that is, east-west and north-south velocity components and vertical velocity. The multi-beam arrangement constitutes a much more effective measurement of the current.

5. What do Cannes coastal currents require for high-quality measurement?

Material Reliability

The instruments should be made from reliable materials so that the measurement of Cannes coastal currents can be done qualitatively. For instance, the casing of the ADCP should be made from material that can resist corrosion since marine environment conditions in the Mediterranean Sea near Cannes is very corrosive due to the high salt content. The material best suited for this purpose would be titanium alloy. Titanium alloy has a very high strength-to-weight ratio; thus, it will be able to bear the pressure of a column of water on it at depth without being overly heavy. It is highly resistant to corrosion even in seawater, which causes corrosion in a number of metals over time. This corrosion resistance will provide long-term durability to the ADCP and reduce frequent maintenance and replacement needs.

Small in Size and Light in Weight with Low Power Consumption

The ADCP meter has to be of small size and light in weight. The smaller and lighter a device is, the easier it will be to deploy on a ship, attached to a buoy, or on the seabed. This also makes it more versatile for different measurement scenarios. Besides this, low power consumption is also very important. In many instances, ADCPs can be deployed to remote locations or for long-term monitoring where access to a continuous power source is limited. A low-power-consuming ADCP can operate for extended periods with batteries or other limited power sources, such as solar panels.

Low Cost

Especially for large-scale measurement, a low-cost ADCP is highly in demand. This is because, with decreased cost, more and more research institutions, environmental monitoring agencies, and even private persons can afford access to ADCPs. In addition, a low cost enables multiple ADCPs to be deployed in various locations to get a much more precise picture of current patterns in this area.

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

Based on Usage

• Ship-borne ADCP: This type is installed on a moving ship. It is especially effective in the performance of large-scale surveys of Cannes' coastal currents. Because the ship will be moving along the coast, the installed ADCP profiler will make continuous measurements of the current profile with data over extensive areas. In this regard, the outcome is advantageous to map the general patterns that occur within the coastal current.
• Bottom-mounted (Sit-on-bottom) ADCP: These are placed on the seabed. They are appropriate for the long-term monitoring of current conditions at a particular location. For example, if researchers want to consider the long - term effects of a specific coastal development on the local currents, a bottom-mounted ADCP shall be deployed at the site. It can provide continuous data on the current velocity and direction at that fixed location over an extended period.
• Buoy-mounted ADCP: Buoy-mounted ADCPs are attached to floating buoys. They are helpful in current measurement where ship access may be difficult or for monitoring the movement of water masses over a large area. The buoy can drift with the currents and provide data regarding the movement of the water column as a whole.

Based on Frequency

• 600kHz ADCP: this would be more suited for flow measurement in water which is of fairly shallow nature. It's mainly used where water depth could reach a limit of around 70 meters. Because it has higher frequencies, much of the resolution concerning the upper water column becomes enhanced in the recorded flow. During deployments close to shore from Cannes where most of the times the sea is within that range, a 600kHz ADCP can carry out the intended function with ease.
• 300kHz ADCP: Lower frequency and thus deeper into the water column. It will be suitable to about 110m of water depth. This frequency can be a good compromise for areas around Cannes with water depths of intermediate values, given the balance between depth penetration and measurement resolution.
• 75kHz ADCP: It is a low-frequency ADCP suitable for deep waters with a measurement capacity of current depth up to 1000m. Though normally not this deep in waters off Cannes, one might well operate the 75kHz ADCP in areas closer to the edge of the continental shelf or in the deeper parts of the gulf during studies that required increased range. Some of the very well-known brands in the market include Teledyne RDI, Nortek, and Sontek.

However, for those looking for an affordable but quality option, the Chinese brand China Sonar PandaADCP is highly recommended. It is made from all-titanium alloy materials and is very corrosion-resistant and durable. Its price-to-performance ratio is truly remarkable, making it an ideal choice for various applications, especially for those on a budget. It belongs to the category of economic-type ADCP. You can find more information about China Sonar PandaADCP on their website: https://china-sonar.com/.

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