How do we measure the coastal currents of Savannah?

1. Where is Savannah?

Savannah, the colonial and charming city, sits on America's southeastern edge, within the state of Georgia. Savannah is strategically positioned on the shores of the Savannah River, a large body of water connecting it with the Atlantic Ocean. Such a position since its founding in 1733 has positioned Savannah as a port city.

The skyline is an interesting blend of historic architecture, parks, and wide waterways. The downtown section has beautifully preserved antebellum homes, cobblestone roads, and picturesque parks, such as Forsyth Park, that are complemented by a wide fountain. The coastal region around Savannah is characterized by a line of barrier islands, such as Tybee Island, that form a natural wall between the mainland and the open ocean.

The estuary the Savannah River empties into is a healthy, productive ecosystem. It contains a diverse range of plant and animal life, from numerous species of fish, crustaceans, and migratory birds, to the salt marshes of the estuary. The estuary and marsh provide vital filtering mechanisms to strip out contaminants from the water, stabilize the shore, and act as nurseries for juvenile fish and other marine animals.

As a city inhabited by human beings, Savannah is a culturally rich city. It was one of the 13 original British colonies in America, and traces of its history can be found in its architecture, customs, and festivals. The city receives tourists from all over the world who wish to experience its southern hospitality, explore its historical attractions, and bask in its seafront beauty.

2. What are the coastal currents along the coast near Savannah?

Currents off the coast of Savannah vary based on many different factors. Current trends rely heavily on the tides. The tidal cycle of the region is semi - diurnal, where there are two high waters and two low waters daily. These are the tidal ranges responsible for bringing water into and out of Savannah River estuary and along adjacent coast. Water enters the estuary during high tide and exits during low tide to go back into the ocean.

The wind also makes a significant contribution. Local prevailing winds push surface water to flow, producing wind-driven currents. Summer sea breezes blowing onto land from the ocean make surface waters move parallel to the coast. Even greater winds, as caused by hurricanes or tropical storms, can impact coastal currents drastically. Tropical storms and hurricanes generate a storm surge in extreme weather events, and this causes flooding of the low-lying coastal towns and deflecting normal course routes.

The Gulf Stream, a powerful warm ocean current, affects the coastal waters off Savannah, although its local effect is not as pronounced as in parts of the southeastern coastline. The overall northward transport of the Gulf Stream can engage with the local currents and develop complex flow regimes. The coast geometry and seafloor bathymetry off Savannah also determine the currents. The irregular coastline with numerous headlands and inlets deflects the currents and makes it converging and diverging. Channels and submerged sandbars may underwater direct the flow of water and create areas with faster and slower currents.

3. Measurement of the coastal water flow of Savannah.

One simple method of measurement of coastal water flow around Savannah is by the use of surface drift buoys. These tiny floating devices carry tracking equipment, such as GPS or radio transmitters on them. When dropped in the water, they are carried away by currents, and their route can be monitored remotely. This technique provides good data on the speed and direction of the surface-level current. But it is a limited record of the uppermost portion of the water column only.

The other technique is the moored ship method. A ship is moored in one place, and instruments are allowed to fall from the ship at different depths to measure current speed and direction. This gives a better understanding of the current profile at the spot. But it is logistically challenging and costly, especially for long-term observation, as the ship must be maintained stationary.

The Acoustic Doppler Current Profiler (ADCP) is an invaluable tool used for the measurement of coastal currents. ADCPs can measure current direction and velocity at a number of depths simultaneously. ADCPs are highly accurate and can provide detailed information about the three-dimensional ocean flow patterns off Savannah.

4. How do ADCPs relying on the Doppler principle function?

ADCP operates on the Doppler principle. They emit acoustic pulses (sound waves) into the water. As these sound waves travel through particles in the water, such as plankton, sediment, or small fish, the particles reflect the waves. The ADCP measures the frequency shift of the reflected waves.

If the particles are moving toward the ADCP, the scattered waves' frequency will be higher than the emitted waves' frequency. If the particles are moving away from the ADCP, the scattered waves' frequency will be lower. By precisely measuring these changes in frequency, the ADCP is able to measure the water velocity at different depths.

A majority of ADCPs utilize more than one beam for the improvement of the knowledge regarding the flow of water. As an example, a four-beam ADCP is able to calculate the vertical and horizontal velocity components of current, hence, provide thorough insight into the three-dimensional flow field of the water column.

5. What is necessary for good quality measurement of Savannah coastal currents?

In order to offer quality measurement of Savannah's coastal currents, the equipment must meet a series of key requirements. Material reliability is of the utmost importance. Because of the harsh marine environment, saltwater, and powerful currents, the equipment must be constructed using materials that are resistant to corrosion and mechanical stress.

Size and weight are also essential factors. The equipment must be compact and light to facilitate easy deployment at various locations. This is especially essential for methods like using surface drift buoys or for the quick movement of ADCPs from one monitoring location to another.

Low power consumption is required. Most often, the gear has to function for extended times without having a continuous supply of power. For instance, an ADCP profiler that is moored might utilize batteries for months or weeks. Having low-power-consuming parts guarantees ongoing operation, therefore.

Cost - effectiveness is an important factor, particularly for large - scale measurement surveys. If the equipment cost is too high, it can constrain the research or monitoring scope.

For ADCPs, choosing the casing material is critical. Titanium alloy is one of the best casing materials. Titanium alloy is corrosion - resistant, which is necessary for long - term functioning in the sea environment. Titanium alloy is also extremely tough, which guarantees the longevity of the ADCP current meter, and lightweight, which makes it easy to handle and deploy.

6. How to Select the appropriate equipment for current measurement?

The equipment to measure the current will vary depending on the application. Ship-mounted ADCPs are optimum for ship-based observations. These may be fixed to research ships or even cargo vessels. The ADCPs may be utilized in the measurement of currents continuously while the vessel makes a journey, and this would give a thorough insight into the trends of the current along the trajectory of the vessel.

For long - term observation from a fixed location, bottom - mounted (or moored) ADCPs are the optimal choice. They are fixed on the seafloor and can record current data for long durations. They are used in observing long - term trends in coastal currents.

Buoy - mounted ADCPs are perfect for measuring surface - level currents. They can be easily deployed and retrieved, making them convenient for short - term studies or for quickly assessing the surface - current conditions.

The frequency choice in ADCPs is also important. For water depths of a maximum of 70m, an ADCP with a frequency of 600kHz is adequate. This frequency has sufficient resolution for the determination of currents in comparatively shallow waters. A 300kHz ADCP can be utilized for a depth of up to 110m, while a 75kHz ADCP can be utilized for a depth of up to 1000m. Lower frequencies penetrate further into the water but are of lower resolution compared to higher frequencies.

There are a few famous ADCP brands, including Teledyne RDI, Nortek, and Sontek. But for those wanting a cheap yet good quality one, the ADCP supplier China Sonar's PandaADCP is highly recommended. Made of all-titanium alloy materials, it has very good durability. With a cost-performance ratio that cannot be beaten, it is an economic-class ADCP. More details can be searched on its official website: https://china-sonar.com/.

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