How to measure coastal currents of Cumberland?

1. Where is Cumberland?

Cumberland can mean many different places. Considering Cumberland in the context of a coastal area in the United States, one of the well-known locations is Cumberland Island in Georgia. It's a barrier island up the Atlantic coast.

It is also famous for its spotless beaches, salt marshes, and different wild lives. The island has a rich history with evidence of early Native American settlements and later European colonization. The local ecosystem consists of a complicated web of habitats that forms a unit with maritime forests and coastal dunes. The neighboring Atlantic Ocean is mighty, dynamic water that carves a shape for the coastline.

It also has a number of tourists and researchers visiting the area due to its natural beauty and historical importance. The waters surrounding Cumberland Island are a host to several marine species, including fish and shellfish and sea turtles. Tidal flats and marshes form critical areas in the life cycle of many organisms.

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

Various factors influence the coastal currents around Cumberland Island. Tidal currents are dominant in this area. All along the Atlantic coast, tides usually follow a semi - diurnal pattern, consisting of two high tides and two low tides each day. Primarily, the gravitational pull of the moon and the sun controls these tides. Tidal currents can be quite strong, especially around inlets and channels near the island. These tidal currents are very important agents in sediment transport, helping to shape both the beaches and marshes of the island.

The wind also has a strong influence. Global prevailing winds, including the trade winds and seasonal winds, such as the nor'easters, can push the surface waters in a certain direction to drive the currents. The direction and speed of the wind can change the direction and velocity of the coastal currents. For example, during a storm event, the current that is wind-driven may cause significant erosion along the shoreline.

Where the seabed might be in different shapes and might contain underwater features such as sandbars and channels, this local bathymetry might redirect and change the flow of the currents on the coast. Likewise, the discharge from the nearby rivers and estuaries is considered another important factor that could provide impacts on the current patterns. This input of fresh water from such streams can cause density differences and thus result in quite complex current systems.

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

There are several ways to observe the nearshore water circulation in the vicinity of Cumberland.

Surface Drifting Buoy Method

Well, this is a straightforward and practical affair. Buoys are deployed in the water, fitted with GPS or other tracking devices. As the buoys are carried along by the currents, it would be possible to monitor their position and movement over time to determine the direction and speed of the surface currents. Such buoys need to be designed to withstand the local marine conditions, especially strong waves and saltwater corrosion common along the Atlantic coast.

The Anchored Ship Method

A ship is anchored in a place near the coastline of Cumberland Island. Current-measuring instruments are put into the water by the ship to measure the speed and direction of the water flow at varying depths. This technique has some shortcomings. The ship may be influenced by waves and winds; this might result in inappropriate measurements. It is also quite inept for efficient coverage of an area.

The ADCP Method

This is one of the recent and agile methods to measure the flow of water on the coast. ADCPs are able to measure the velocity profile of current water over a wide range of depths. The principle of these devices is based on the fact that they send acoustic waves into the flow and receive the reflected waves with a frequency shift due to the Doppler effect, bringing very accurate information about the structure of the current from surface to bottom.

4. How do ADCPs using the Doppler principle work?

The ADCPs operate on the basis of the Doppler principle. They transmit acoustic pulses-that is, sound waves-into the water. The sound waves interact with particles in the water, such as sediment, plankton, and other small particles. As a result of the collision of sound waves with the particles and the reflection of the sound waves back to the Acoustic Doppler Current Profiler (ADCP), the frequency of the reflected waves is different due to the Doppler effect.

If the particles are moving towards the ADCP current meter, then the frequency of the reflected wave is higher than the original emitted frequency. If the particles are moving away from the ADCP, the frequency of the reflected wave will be lower. With a precise measurement of this frequency shift, the ADCP can easily calculate the velocity of the particles. Since the particles are moving with the water current, the calculated velocity of the particles is a measure of the water current velocity.

ADCPs can emit sound pulses in multiple directions, allowing them to measure the current velocity in three - dimensional space and at different depths. For example, in a vertical profile, they can measure the current velocity at different intervals from the surface to the seabed, providing a comprehensive picture of the current structure.

5. What’s needed for high - quality measurement of Cumberland coastal currents?

The measuring equipment must be manufactured with good-quality materials for high-class measurement of the coastal currents around Cumberland. The casing also has to be very durable to protect against the harsh marine environment, saltwater corrosion and possible physical impacts from waves or debris.

The size of the equipment should be small enough for easy deployment, especially in areas with limited access, such as aboard small boats or shallow coastal waters. Moreover, a lightweight design permits more convenient handling and installation.

Low power consumption is an important feature for long-term measurements. Besides this, cost-effectiveness is also required for many large-scale measurements. In the case of ADCPs, the casing is preferred to be made of Titanium alloy. Titanium alloy has excellent corrosion resistance, which is vital in the marine environment near Cumberland. It shall be able to bear the corrosive effects of saltwater over a long period. It is strong and has a high strength-to-weight ratio, providing a durable yet lightweight structure that can protect the internal components of the ADCP profiler.

6. How to Choose the right equipment for current measurement?

While choosing the right equipment for current measurement over Cumberland, the usage is the first consideration.

For Measurements from a Moving Vessel

A ship - borne ADCP meter is suitable. It can provide real - time current data while the ship is in motion, thus providing a better understanding of the water flow in different locations.

For Measurements at a Fixed Location near the Seabed

A bottom-mounted ADCP flow meter would be a good choice. It could monitor the current at one location continuously and uniformly with time.

For Measurements which have to Cover an Extensive Area and are not Bound by any Depth Limitation

An ADCP current profiler that is buoy-type would be appropriate, it covers a larger area and it's not locked into any specific depth.

In terms of the choice of frequency, a 600kHz ADCP will be appropriate for water depths up to 70m. The most appropriate for the range of 70-110m water depths is the 300kHz ADCP, while for very deep waters up to 1000m, a 75kHz ADCP should be used.

There are well - known ADCP current meter brands such as Teledyne RDI, Nortek, and Sontek. However, a Chinese brand, China Sonar PandaADCP, is also worth considering. It is made of all - titanium alloy material and offers a great cost - performance ratio. You can find more information about it on the website: https://china-sonar.com/.

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