How to measure the coastal currents of El Hur?

1. Where is El Hur?

El Hur has a special geographical positioning being a coastal zone along a piece of coastline with an inviting bay. This is further defined by areas of land which surround El Hur in a mix of pure sandy beaches to areas with coastal scrub and grassland adding to beautification of this place.

The locals here live with the sea. Their cultural identity is deeply enshrined in maritime activities, mainly fishing, a resource they have survived on for decades. The bay area off El Hur teems with life: numerous species of marine animals, colorful schools of fish swimming abreast in the clear waters, and crabs scuttling over the sand and rocky bottoms. Seabed topography is highly variable, ranging from areas with a gentle slope and including small rocky outcrops; all this influences water movement and circulation.

The waters of El-Hur form a part of an extended oceanic network. The ocean currents that flow from remote areas reach the coast, carrying water masses with distinct properties, such as temperature and salinity. Tides also have an immense effect on the structure of the coast. Its regular cycles outline the flow and the recession of the water at a certain coast, from the mere sediment distribution to the habitats of several marine organisms.

2. What is the situation of the coastal currents near El Hur?

Various are the factors influencing the coastal currents near El Hur. The tides are one of the major forces determining the normal up-and-down movement of water along the coast. The range of tide controls the strength and width of the tidal currents. In places, high tide rushes in more fiercely, while at low tide it recedes and complicates the flow patterns.

Another important factor is the wind. The general winds in the area may be able to push the surface waters, forming surface currents and interacting with other deeper layers of water. For example, onshore winds could force the water toward the coast, influencing the deposition of sediment and, consequently, nutrient distribution. Likewise, the particular topography of both the coastline and the seabed also plays a huge role. Some of the physical causes of these discrepancies at Hur include currents deflected at headlands and funnelling around bays and underwater ridges. That bay shape close to El Hur is directing the water at specific directions on the natural pathway of flow-areas of reduced or increased flow velocity.

Besides, the interaction of the coastal currents with the oceanic currents approaching from the open sea is important. These larger ocean currents may join the local coastal currents and bring changes in temperature, salinity, and flow characteristics, which further complicates the current situation.

3. How to observe the coastal water flow of El Hur?

Surface Drifting Buoy Method

This is the method of deployment of buoys on the water surface, which are allowed to drift freely with the currents. Their position, as determined by satellite or other positioning systems over time, yields information on direction and speed of surface currents. On the other hand, it has a limitation since it focuses majorly on the surface and may not give ample details on the currents through the water column.

Moored Ship Method

In this technique, a ship is moored in a particular position in the coastal area. The instruments on the ship measure the flow of water around it. While it can provide detailed information for the surroundings of the ship, the mere presence of the ship interferes with the natural flow to some extent, and it can only cover an area relatively small around the mooring point.

Acoustic Doppler Current Profiler (ADCP) Method

ADCP current meter is an advanced and convenient way of measurement of the coastal currents. It makes use of acoustic waves to measure simultaneously the velocity of water at different depths. This allows it to build a detailed profile of the current from the surface down to a certain depth, giving full insight into the structure of the flow of the coastal water. For example, this methodology, compared with others, can cover larger vertical range in most cases or suffer lesser from external interferences, thus enabling good efficiency in its application for observations of coastal currents near El Hur.

4. How do the ADCPs following the Doppler principle work?

The ADCP methods adopt this principle of action. They issue acoustic pulses through water. These sound waves, while interacting with moving particles in the water-suspended sediment or small organisms-change in frequency due to the Doppler effect. The ADCP current profiler is designed to detect and measure this frequency shift. With multiple transducers oriented in different directions, it can determine the velocity components of the water in various directions, including horizontal and vertical. It does so by the capability to obtain the three-dimensional flow field of coastal currents. This ADCP flow meter continuously emits the acoustic pulses and records, at regular periods, reflected signals; therefore, it does permit one to create a time series of the data in the current velocities at depth, thereby offering, in such a manner, an excellent record of the variability in the time-space continuum of currents.

5. What is necessary to have a qualitative measurement of El Hur coastal currents?

In measuring the coastal currents around El Hur, several things are very important concerning the equipment: material reliability of the equipment, which needs to be able to work in the harsh marine environment, facing corrosion by seawater, the impacts of waves, and changes in temperature and pressure. Small size is advantageous because it makes deployment and handling easier on boats, buoys, or any other platform.

Another important factor is light weight, which would ease the installation process and minimize the load requirement. Low power consumption is a major requirement, especially for the case of long duration measurements or using battery-powered outfits. Cost is a consideration for ensuring that the ADCP meter enables many and larger-scale measurements. In such regard, the casing of the ADCP profiler shall be of titanium alloy. The choice of titanium alloy has outstanding advantages. 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. Moreover, its relatively low density helps in keeping the overall weight of the equipment in check while maintaining its structural integrity.

6. Selection of Appropriate Equipment for Current Measurement?

Usage-based

• Shipboard ADCP: It will be useful if the measurements are to be made while the ship is in motion or stationary in the coastal area. The instrument can continuously record data when the ship cruises along different locations on the coast and thereby map the current patterns over a reasonably larger area. 
• Bottom-mounted ADCP: Suitable for fixed-point measurement from the seabed and thus may deliver information about current passing above its head on the near-bottom conditions, important to understand in studies of sediment transport and other benthic processes.
• Buoy-mounted ADCP: These are mounted on buoys floating on the water surface, and they measure currents from the surface downwards. It is useful for observing the variation of the current of the surface and the upper layer since this type is often deployed where long-term monitoring is needed without the requirement of a ship's presence at the site.

Based on Frequency

• Water depth within 70 meters merit consideration of a 600 kHz ADCP. The increased frequency allows shallow water to resolve current flow at high resolution from near the surface right down to a depth of interest.
• The ADCP operating at 300 kHz will be more relevant at water depths of up to 110 meters since it would more effectively cut through the water column in its measurement of the currents across that depth range.
• Where there is need for measurements up to 1000 meters of depth, one requires an ADCP with 75 kHz frequency to reach greater depth and yield satisfactory data for the current flow at such levels.

There are several well-known ADCP brands in the market, such as Teledyne RDI, Nortek, and Sontek. However, for those seeking high-quality yet cost-effective options, the China Sonar PandaADCP is worth considering. It is made entirely of titanium alloy material, ensuring excellent durability and performance in the marine environment. With its incredible cost-performance ratio, it offers a great choice for measuring the coastal currents of El Hur. 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.