Measurement of the Coastal Currents of Beziers

1. Location Description

Beziers is the most picturesque medieval settlement on what used to be Hérault in southern France. Geographically, it commands an elevated positioning overlooking the sweeping planes and facing at an angle over the beautiful expanses of Languedoc-Roussillon and in that manner assumes more the look and character of beautiful Mediterranean climes contrasted with rustic countryside scenery and ambience.

The region is rich in historical and cultural heritage. With its history tracing back to the ancient Roman times, Beziers has a lot of historical landmarks, including the Saint - Nazaire Cathedral, which shows the city's past glory. The local culture is alive, filled with festivals, local cuisine, and traditional crafts.

Geographically, in the immediate waters, Beziers is not a coastal city but is near the Mediterranean Sea. The nearby coastal areas are characterized by beautiful bays and inlets. In the vicinity lies the large coastal lagoon known as the Étang de Thau. This lagoon is connected to the Mediterranean Sea with channels, creating a unique aquatic ecosystem. The coastal waters are a mix of calm lagoon-like areas and the more dynamic waters of the open sea, which are influenced by the tides and the general circulation patterns of the Mediterranean.

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

Besides tides, there are numerous other major factors responsible for coastal currents, especially near Beziers. One major factor is tides. Although the tidal range is not as significant in the Mediterranean Sea compared to some other seas, there is still periodic movement of water that results from tides. During periods of ebb and flow, the tides either reinforce or oppose the other current-forming forces.

The other important factor is the wind. Regional prevailing winds like the Mistral and Tramontane can drive the surface currents. When the winds are strong, it may push the water along, developing large-scale movement of the coastal waters. For example, a persistent on-shore wind may cause an accumulation of water near the coast, while an off-shore wind can result in the movement of water away from the land.

The shape of the coastline and the bathymetry of the seabed further influence coastal currents. Irregularities in the shoreline, including headlands and bays, can cause a deflection in currents and a change in direction. The depth of the water, determined by the bathymetry, influences the speed and flow pattern of the currents. Deeper waters may allow for faster-flowing currents, while shallower areas can slow them down.

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

Surface Drifting Buoy Method

It involves deploying the buoys on the water surface. The buoys will carry with them tracking devices such as GPS. If the buoy is taken by the water current, it moves, carrying its tracking device with it and its position at different instances is recorded. By analyzing the movement of the buoy, one can estimate the direction and speed of the surface currents. This method is limited to the surface water currents only because it does not give any detail about the currents in other depths.

Anchored Ship Method

The anchored ship method involves a ship anchored at a place. From it, current-measuring instruments are thrown in the water to different depths. These instruments could measure the speed and direction of currents at each depth. The information obtained from this technique gives a far better view about the vertical profile of the currents but is again confined to a single point where the ship is anchored.

Acoustic Doppler Current Profiler (ADCP) Method

The ADCP method has recently gained popularity. In ADCPs, ultrasonic waves of short periods are employed in determining the current velocity at different water levels. They have been deployed from ships, moored on the seabed, and installed on floating platforms. The ADCPs offer a more efficient and accurate way to measure currents in larger areas compared to the previous two methods. They can provide continuous measurements of the current profile from the surface to a certain depth and, thus, are favored for most modern coastal current studies.

4. How do ADCPs Using the Doppler Principle Work?

ADCPs work on the basis of the Doppler effect. The instrument sends out a sequence of acoustic pulses into the water. As these sound waves meet the particles-sediment, plankton, and small bubbles in the water-the particles scatter the sound waves back to the ADCP.

If the particles are in motion-that is, being conveyed by the water current-the scattered sound waves will have a different frequency from the frequency of the emitted sound waves. This frequency shift is called the Doppler shift. By measuring the Doppler shift, the ADCP can calculate the velocity of the particles, and hence the velocity of the water current where the particles are present.

Generally, ADCPs come with more than one beam-3 or 4 beams. Since each beam is set to measure the Doppler shift in different directions, an ADCP is thus capable of delivering three-dimensional series of velocity from a water current. It offers better resolution of flow conditions from currents where the horizontal and vertical components may vary greatly.

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

Equipment Reliability

For the measurement of high-quality Beziers coastal currents, the ADCP equipment must be highly reliable. Since the ADCP is to operate in a marine environment, which is usually harsh because of saltwater corrosion, temperature variations, and wave action, the materials used in the ADCP must be able to bear such conditions.

Size, Weight, and Power Consumption

The size of the ADCP should be small; a smaller size will allow for easy deployment and minimal interference with the natural flow of the water. The design should also be lightweight, especially when it comes to being deployed from a small vessel or attached to a floating platform. In addition, the power consumption should be low. This is important for long-term and autonomous measurements to reduce the need for frequent battery replacement or interconnection with a large-scale power source.

Cost-Effectiveness

The cost of the ADCP should be as low as possible, especially for large-scale measurements. A low price enables wide deployment, offering more information on the currents at the coast.

Casing in Titanium Alloy

The casing is one of the most important features of an ADCP. A casing made of a titanium alloy is highly recommended. There are a number of reasons for this: Titanium alloy is very resistant to corrosion, an important feature when a piece of equipment may be exposed to saltwater for a long time. It has a high strength-to-weight ratio, which means it can be both strong enough to protect the internal components of the ADCP and relatively lightweight. This combination of properties makes the titanium alloy the perfect material for ADCP casing, warranting reliability and durability in rough marine conditions at Beziers.

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

Based on Usage

Ship-borne ADCP: This type is fitted for large-scale surveys in large areas. It is fixed on a ship and can measure currents while the ship is on its movement; hence, it's ideal to delineate current patterns in large scale.

Bottom-mounted ADCP: The other type is also referred to as either a moored or bottom-deployed ADCP, which is placed at the seabed. This form is good to go for making long-term fixed-location measurements. It can provide current conditions continuously in terms of a specific site it deals with.

Float-mounted ADCP: These are mounted on floating platforms or buoys. They can be applied for areas that have either impractical fixed-position or ship-based measurements, for instance, locations with strong current conditions or sites very far from one another.

Based on Frequency

Frequency is an important factor to be considered in an ADCP:. The 600kHz ADCP serves best for water as deep as 70m and gives higher resolution in shallow water. In waters as shallow as 110m, the balance between resolution and depth range is reasonable, hence ideal, with a 300kHz ADCP. For waters as deep as 1000m, the appropriate apparatus is the 75kHz ADCP since this lower frequency penetrates deeper into the water.

Currently, there are a good number of well-acknowledged ADCP brands such as Teledyne RDI, Nortek, and Sontek. However, one great China Sonar ​PandaADCP will be developed for those looking for an affordable yet quality ADCP. What's more, it is made entirely out of a titanium alloy-a difficult material that is durable enough to assure dependability. In general, this is an economic ADCP that is offering good performance with incredible cost-effectiveness. Please visit their website for more information at ​https://china-sonar.com/.

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