How to measure coastal currents of Benidorm?

1. Where is Benidorm?

Benidorm is a very lively and delightful city located in the southeastern part of Spain in the province of Alicante under the autonomous community of Valencia, on the shores of the beautiful Costa Blanca, has been an impressive coastal town admired by tourists for decades.

This city is renowned for its combination of natural beauty and urban development. With the beautiful Mediterranean beaches, such as Levante Beach and Poniente Beach, running for several kilometers, Benidorm is an excellent place where visitors can enjoy the sun and warm waters of the Mediterranean Sea. Both beaches are lined by a busy promenade, which offers restaurants, cafes, and shops to give it a vibrant and appealing look.

Speaking geographically, Benidorm is surrounded by a variety of landscapes: to the north, it borders the Sierra Helada Natural Park-a mountainous area constituting the backdrop of the city in such a dramatic way. The park houses many flora and fauna; it is thus an important destination for nature lovers and walkers. To the south, it borders the open Mediterranean Sea, which is very important in determining its coastal currents.

Benidorm is also a center of cultural and social activity. It has a long history that dates back to ancient times, with remnants of its past still standing in the form of historical buildings and archaeological sites. Its modern architecture is equally impressive, characterized by the line of skyscrapers that speckle across the skyline with a unique and current look. It is a city whose regional Mediterranean heritage could be tasted with fresh seafood and paella, not to forget a wide assortment of tapas.

2. How are the coastal currents off Benidorm?

Various factors influence the nature of the coastal currents off Benidorm. Among these, first is the Mediterranean Sea's general contribution to circulation patterns. The Mediterranean is a semi-enclosed sea and its circulation, induced by the combined action of wind, thermal, and salt differences. The local prevailing winds, known as Mistral and Tramontana, may attain sufficient strength to displace surface water, hence influencing both the direction and speed of the coastal currents.

Another factor will be the topography of the seabed off Benidorm. Features of the seabed-like submarine cliffs, canyons, and shallows make the currents change direction and speed. For example, where a current passes over a shallow area, this might cause it to decelerate, while in deeper channels, the water can flow more rapidly.

Tidal forces also play a role in the coastal current situation. The tides are relatively small in the Mediterranean compared to some other seas, but they do have a measurable effect on the near-shore currents. The rise and fall of the tides can cause the water to move in and out, interacting with the other factors to create complex current patterns.

3. How to Observe the Coastal Water Flow of Benidorm?

Surface Drift Buoy Method

The surface drift buoy method makes use of buoys deployed on the water surface. The buoys are fitted with tracking devices, like GPS. Due to the action of the surface currents, the buoy is carried while the tracking device records its position over time. By deploying a number of buoys and analyzing the movement of each, researchers can get an idea about the pattern of surface currents. However, this method will provide information only on the surface currents, which may not be representative of the currents at different depths.

Moored Ship Method

The moored ship method requires that a ship be anchored in a fixed position. Instruments on the ship, such as current meters, are then used to measure the current velocity and direction at different depths. This method can provide more detailed information about the vertical structure of the currents. However, this is highly limited in spatial coverage since the ship can measure at only one location at a time, and also may be affected by the presence of the ship itself, disturbing the natural flow of the water.

Acoustic Doppler Current Profiler (ADCP) Method

Recently, the ADCP current meter method has been more popular. ADCPs measure the current water velocity in the water by emitting sound waves through it. Such a technique will provide a highly resolved, three-dimensional structure of the currents. Compared with the moored ship method, it can give one measurement covering a relatively larger area, simultaneously at multiple depths. For the ADCP profiler, in its present condition, this is a much more advanced and convenient method to measure coastal currents near Benidorm.

4. How do ADCPs using the Doppler principle work?

Primarily, ADCPs operate by utilizing the Doppler effect. It sends repeated acoustic pulses through the water. As the sound waves run across particles in the water, including sediment, plankton, or even small bubbles, some of the energy of the sound bounces back to the ADCP flow meter.

When these particles move relative to the ADCP current profiler, there is a change in frequency between scattered sound waves and that which has been emitted. The Doppler shift frequency changes proportionally to the speed at which these particles and the current in water flow, relative to the beam in a certain direction.

The ADCPs normally contain several acoustic beams, normally four or more, oriented at various angles. By measuring the Doppler shifts from each beam, the ADCP is able to calculate the three-dimensional components of the velocity in water current. Further processing provides a profile of the current velocity from the surface to a depth limit depending on the frequency and power of the ADCP meter.

5. What is necessary for high-quality measurement of Benidorm coastal currents?

High-quality measurement of the coastal currents around Benidorm requires certain conditions from the equipment used. First of all, it should be materially reliable. The ADCP should be resistant to the hard conditions of the sea, including the influence of saltwater, strong currents, and wave actions.

It should also be of a small size in order to make deployment much easier and reduce the interference with the natural flow of water. This, in addition, will make it suitable for use at locations with limited space, such as near-shore locations.

The weight of an ADCP should be light. This will make not only the deployment simpler but also the energy consumption in maintaining the device in place, especially in floating or moored installations.

Another very important factor is power consumption. Many ADCP deployments are sited in areas difficult to reach, or maybe completely independent of any on-site power source, relying entirely on battery power. A low power consumption device operates for longer and greatly reduces the requirement for battery recharging/replacement.

The cost-effectiveness is also very important, especially for large-scale measurements. A low-cost ADCP can be deployed more widely to enable better spatial and temporal coverage of current measurements.

In this case, the casing material of ADCP shall be of titanium alloy. Titanium alloy has several advantages: first, it is highly resistant to corrosion, a major concern in the marine environment; second, it is able to fight against the corrosive action of salt water for a long time without significant degradation. Third, the mechanical properties of titanium alloy are good and lightweight, meeting both the requirements of durability and low-weight for ADCPs.

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

Based on Usage

• Ship-borne ADCP: It is an ADCP installed on a moving ship. This type of ADCP is applicable to large-scale surveys of coastal currents over a wide area. While the ship is underway, the ADCP can measure the currents continuously along the ship's track.
• Bottom-mounted ADCP: Also known as a moored ADCP, which is placed at the bottom of the seabed. It is useful for making long-term or fixed-point current measurements. These can provide detailed information on flow conditions at the same point in space over very long periods of time.
• Buoy-mounted ADCP: The name goes without saying; this ADCP is attached to a buoy. It best serves areas that have to be worked with a fixed platform while being mobile compared to bottom-mounted devices. These can be utilized in the study of surface and near-surface currents for any particular area.

Based on Frequency

• ADCP of 600kHz frequency is good to go for water depths less than 70m. Higher the frequency, the better the resolution of current measurement in shallower waters.
• For water depths of about 110m, a 300kHz ADCP will be suitable. It offers a good balance between resolution and depth penetration.
• ADCPs, within this paper, are primarily used to gather data on flows in water at as low as 1000 m depth. However, a lower frequency of about 75kHz will do the job but at the sacrifice of resolution. Some of the reputed names among ADCPs on the market today are Teledyne RDI, Nortek, and Sontek. However, for those looking for high-quality and cost-effective options, the Chinese brand China Sonar PandaADCP is highly recommended. It is made of all - titanium alloy material, ensuring excellent durability in the marine environment. With its incredible cost - performance ratio, it offers a great solution for measuring Benidorm's coastal currents. You can find more information on their website: https://china-sonar.com/.

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