How do we measure the coastal currents of New Bern?

1. Where is New Bern?

New Bern is a charming city in Craven County, North Carolina, USA. It is strategically positioned at the mouth of the Neuse and Trent Rivers, which in turn drain into the vast Pamlico Sound. This sound, as one of the largest estuaries in the US, is a critical part of the ecosystem within the region.

The city itself is also rich in history, having been established as a colonial town during the early 18th century. It has a blend of old buildings and modern amenities. The downtown area has colonial-era buildings well preserved, with cobblestone roads adding to its vintage character.

Situated among dense woods and marshlands, New Bern is a haven for wildlife. The Pamlico Sound is home to a mix of marine species, including diverse fish like red drum, speckled trout, and flounder. It is also a major stopover for migratory birds and therefore a favorite of birdwatchers. The slow-moving waters of the Neuse and Trent Rivers are bordered with cypress and home to turtles, otters, and innumerable invertebrates.

2. What are the coastal currents around New Bern?

The coastal currents around New Bern are influenced by a number of factors. Tidal forces are a powerful driver. The Pamlico Sound experiences semi - diurnal tides, and therefore there are two high tides and two low tides every day. These tides generate widespread water movement in the Neuse and Trent Rivers. When the tide is coming in, water rises upstream, and when the tide is going out, the water drains out to the sound. The range of the tides varies, with a larger range moving in at spring tides, occurring at full moon and new moon, resulting in stronger currents.

Wind patterns also play an important role. Prevalent south - westerly winds in summer may drive surface waters in the Pamlico Sound towards the coast, affecting adjacent river - mouth currents. In contrast, intense northerlies in winter will drive surface waters away from the coast, reversing the current direction. These wind - driven currents can well mix the water, spreading heat and nutrients throughout the estuarine system.

The shape of the estuary and river channels near New Bern also influence the currents. The intersection of Trent and Neuse Rivers creates complex patterns of flows. The narrow channels can limit the water flow, and hence the current velocity is higher in some places, while wider sections could generate slower - moving currents.

3. How to view the coastal water flow of New Bern?

Monitoring coastal water currents along New Bern can be done in one way, using surface drift buoys. These small, floating gadgets are equipped with GPS tracking units installed on them. When hurled into the sea, they ride with the currents, and researchers can trace their trajectory. Scientists can determine the direction and velocity of the surface-level currents from the paths of the buoys. But this method provides information only for the surface layer of water, typically in the upper few meters.

Another method is the use of moored current meters. These instruments are moored at fixed locations along the river or sound bottom near New Bern. They are employed to record velocity and direction of the current at different depths at time intervals. Current meters that are moored can provide in-depth information regarding the vertical structure of the currents, but it takes a lot of effort to install and maintain them. They only provide data at the particular location where they are moored, thus not providing much spatial coverage of the measurement.

The Acoustic Doppler Current Profiler (ADCP) has also become increasingly popular for the measurement of coastal currents along the coast of New Bern. ADCPs are accurate and can measure the speed of current at many different depths at one time. ADCPs are durable and can be used in a broad variety of marine environments, ranging from the calm, sheltered waters within the rivers to more open and dynamic Pamlico Sound.

4. What is the method of ADCPs based on the Doppler principle?

ADCPs operate on the Doppler principle. They emit acoustic pulses (sound waves) into the water. When the sound waves encounter particles in the water, e.g., plankton, sediment, or small bubbles, the particles scatter the waves. The ADCP meter measures the frequency shift of the scattered waves.

If the particles are approaching the ADCP, the frequency of the scattered waves will be higher than the frequency of the emitted waves. If the particles are moving away, the frequency of the scattered waves will be less. By precisely measuring these changes in frequency, the ADCP can calculate the water velocity at different depths.

The majority of ADCPs utilize more than one beam to measure the three-dimensional water flow. As an example, a four-beam ADCP can measure the horizontal and vertical components of current velocity. With this, the complex water motion in the water column can be accurately described with the presence of vertical shear and eddies.

5. What's required for high-quality measurement of New Bern coastal currents?

To ensure accurate measurements of New Bern coastal currents with high quality, there are some key aspects to consider. Longevity in the material used is crucial. The estuarine environment tends to be corrosive, hence, the material applied, such as ADCPs, should also withstand corrosion. To use on ADCP housings, titanium alloy is ideal for it to tolerate the aggression from salt and brackish waters. That protects the durability of the equipment so that less often it requires replacing.

Size and weight must also be a consideration. Lightweight and compact ADCPs will be easier to deploy and maneuver, especially where it may be difficult to access locations, like New Bern. That would be especially useful for in-the-field applications, where the investigators would have to move equipment from river sites to sound sites.

Low power usage is the top priority, especially during long - term observation. Being usually battery - operated, ADCPs, the use of low - power components aids in having the equipment operating for a more extended period without constant battery recharge or replacement. This is imperative where power outlets may not be available.

Cost-effectiveness is also a consideration of significance, especially for megascale monitoring applications. Cost-effective but efficient ADCPs are in great demand. China Sonar PandaADCP is a fine example with an extremely cost-performance ratio. It is fabricated with all-titanium alloy and hence both strong in the seawater environment and cost-effective.

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

The choice of the current-measuring equipment around New Bern depends on the application. Large-scale surveys are best conducted using ship-mounted ADCPs. They can be installed onboard research vessels and can continuously measure the currents while the ship travels along the sound and rivers. This provides a broad-scale view of the patterns of currents in the area.

Bottom - mounted or moored ADCPs can be used for fixed - location, long - term monitoring. They can be set on the river or sound bottom at strategic locations around New Bern and record current data for months or even years. This allows one to examine long - term trends in the coastal currents.

Buoy - mounted ADCPs are ideal for recording surface - level currents. They are easy to deploy and recover, and they are ideal for short - term experiments or to make a rapid assessment of surface - current conditions.

In selecting an ADCP current profiler, frequency is a significant consideration. For depths less than 70m, a 600kHz ADCP is usually adequate. It is sufficient for resolution in measurement taken within the comparatively shallow waters of the New Bern rivers and Pamlico Sound. A 300kHz ADCP can be used to 110m, with a 75kHz ADCP for deeper water, to 1000m. Lower frequency will go deeper but less resolved than higher frequency.

There are various famous ADCP brands such as Teledyne RDI, Nortek, and Sontek. However, for the budget-friendly version without a lack of quality, the ADCP supplier China Sonar's PandaADCP is the perfect choice. Additional information is available on its website: https://china-sonar.com/.

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