How do we measure Everett's coastal currents?

1. Where is Everett?

Everett, a vibrant city in Snohomish County, Washington, enjoys a prime spot on the waterfront of Port Gardner Bay, an inlet of the Puget Sound. It is situated approximately 25 miles north of Seattle and is a key economic and industrial hub in the region. Its development as a city has been closely linked to its access to waterways, and the port has played a key role in its growth.

The area was originally inhabited by the Snohomish tribe, whose livelihood depended heavily on the sea and land. Their legacy continues to be sensed in the names of places and the local culture. The European Americans migrated to the area in the mid - 19th century, attracted by the region's richness in natural resources, particularly timber. Everett's situation on the Puget Sound provided an ideal location for logging and shipping operations. Over time, the city evolved into a major industrial center, with a diverse economy that includes aerospace, manufacturing, and tourism.

These marine waters off Everett are part of the Puget Sound ecosystem, a biologically diverse system of water bodies made up of bays, channels, and inlets. The seafloor topography of the sound is uneven, with shallow water nearshore, deeper basins in the center, and numerous islands and reefs. These create a heterogeneous habitat that supports an impressive variety of marine life, from salmon and herring to seals, sea lions, and an abundant bird community.

2. What is the state of the coastal currents near Everett?

The state of the coastal currents near Everett is governed by a combination of natural and man-made features. Tides play a significant role. The Puget Sound experiences a mixed tidal regime, both semi-diurnal and diurnal. The tidal ranges are quite variable, reaching up to 15 feet in certain places. During high tides, water rushes into Port Gardner Bay, creating strong flood currents. During low tides, water rushes out, creating ebb currents. Both tidal currents are extremely strong in the narrow channels and between the many islands in the sound.

The local waters are also affected by the broader oceanic currents in the region. The flow of water through the Strait of Juan de Fuca, connecting the Puget Sound to the Pacific Ocean, affects the region's temperature, salinity, and current patterns. Prevailing wind patterns, such as the westerlies, can push surface waters toward the shore, and strong easterly winds can produce upwelling, which brings cold, nutrient-rich water to the surface.

Anthropogenic features such as breakwaters, marinas, and ports can disrupt natural current flow. The Port of Everett is one of the largest ports in the Puget Sound and contains a huge infrastructure of piers, docks, and channels. These structures can create local eddies, deflect water movement, and affect sediment and nutrient distribution. For example, the placement of breakwaters to protect the port from large ocean swells can alter the natural bay circulation.

3. How to monitor the coastal water flow of Everett?

Surface Drifting Buoy Method

One of the ways to monitor the coastal water flow near Everett is by utilizing surface drifting buoys. The buoys are designed to float on the water surface and move with the currents. They are equipped with GPS tracking equipment and transmit real - time location data. Scientists calculate from this data the direction and speed of the surface currents. This technique does have its drawbacks. Wind can cause the buoys to drift from the actual current, and the measurement of the subsurface flow will then be incorrect. Also, surface drifting buoys provide information only about the uppermost level of the water column and provide an incomplete picture of the structure of the currents as a whole.

Anchor Moored Ship Method

In the anchor moored ship method, a ship stays at a fixed location. Scientists hang current meters over the side of the ship at different depths to measure the speed of the current. This method provides depth - specific information about the currents. It is, nevertheless, time - consuming and expensive as it entails keeping a research vessel in one location. The data is also only representative of the area in the immediate neighborhood of the ship, and it is difficult to obtain a comprehensive view of the coastal currents over a large area.

Acoustic Doppler Current Profiler (ADCP) Method

The Acoustic Doppler Current Profiler (ADCP) is a more recent, more convenient method of measuring coastal currents. ADCPs use the Doppler shift of sound waves to measure water current velocities at different depths. ADCPs send sound signals into the water column. As the signals bounce off particles in the water, the shift in frequency of the returning signals is used to calculate the velocity of the water. ADCPs possess the ability to provide a complete image of the current structure from the surface to nearly the seabed. This makes them very apt to study the complex coastal currents near Everett.

4. How do ADCPs that use the Doppler principle work?

ADCPs rely on the Doppler effect principle. ADCPs contain piezoelectric transducers, which emit sound waves into the water. As the sound waves encounter particles such as plankton, sediment, or bubbles in the water, a portion of the sound energy is scattered back to the ADCP current meter. The time it takes for the sound waves to travel to the particles and back provides an estimate of the distance to the particles.

The answer to the current velocity measurement is the Doppler shift. If the particles are moving with the water current, the frequency of the sound waves that are scattered and received by the ADCP will be shifted from the frequency of the waves that were sent out. The size of this frequency shift is directly proportional to the water velocity in the acoustic path. To be able to measure three - dimensional velocities, most ADCPs use a minimum of three beams. Modern ADCPs also carry multiple sensors on board, including temperature sensors to compensate for the effect of water temperature on the speed of sound, compasses to record the direction the instrument is pointing, and pitch/roll sensors so that accurate measurements can be taken even in rough seas. The returning signals are amplified, digitized, and processed to calculate the current velocity at different depths.

5. What's needed for high - quality measurement of Everett coastal currents?

To conduct high - quality measurement of Everett's coastal currents, the measuring device needs to meet several requirements. Materials reliability is critical. The ADCP casing needs to be a material with resistance to the aggressive marine environment. Titanium alloy would be an excellent material. It also has high corrosion resistance, which is a necessity for long-term deployment in seawater. Titanium alloy is lightweight and strong, making it easy to handle and deploy. Its strength ensures that the ADCP flow meter will withstand mechanical stress from water movement and potential impacts from trash."

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Size, weight, and power usage are also important. A smaller, lighter ADCP is more versatile, as it can be deployed on a variety of platforms, from small research ships, buoys, or underwater robots. Lower power usage allows longer-term deployments, especially when operating on battery power. Price is also a factor. A cheaper ADCP allows large-scale measurements, increasing the spatial and temporal resolution of the data being gathered.

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

Types Based on Mounting

• Ship - mounted ADCP: Mounted on a moving ship, this type is ideal for large - scale surveys of the coastal waters near Everett. As the ship moves, the ADCP current meter can continuously measure the currents, providing a large - scale picture of the current patterns.
• Bottom - mounted ADCP: Mounted on the seafloor, this is suitable for fixed - point, long - term monitoring. It can provide valuable information on the long - term trends and variability of the currents at a specific point.
• Buoy-mounted ADCP: These ADCPs are mounted on a buoy and are free to move with the water, allowing measurements where fixed-point measurements are not possible. They are deployed in areas with high tidal currents or in regions where the measurement platform needs to be more mobile.

Frequency Selection

ADCP frequency is chosen based on water depth. A 600kHz ADCP will function in water depths as low as 70m. In the relatively shallow coastal waters near Everett, a 600kHz ADCP will provide detailed current profiles. In water depths up to 110m, a 300kHz ADCP would be preferable. This provides a greater range and still provides an acceptable level of accuracy. In dealing with deeper waters in the central Puget Sound, the 75kHz ADCP is the preferable option as it will penetrate more into the water column.

A few of the leading brands of ADCPs in the market are Teledyne RDI, Nortek, and Sontek. But for one who wishes to opt for an affordable yet high-quality brand, the ADCP manufacturer China Sonar's PandaADCP is the best option. Made of all - titanium alloy, it enjoys excellent durability in the marine environment. With an excellent cost - performance ratio, it is an ideal instrument for researchers, coastal managers, and any user needing reliable current measurement data. For more information, refer to https://china-sonar.com/.

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