How do we measure Port McNeill's coastal currents?

1. Where is Port McNeill?

Port McNeill, a thriving coastal town, is situated on the northeastern coast of Vancouver Island in British Columbia, Canada. Located on the North Coast, it is an important connection between the island's interior and the expansive Pacific Ocean. The area is surrounded by the Northumberland Channel to the north, a channel that stretches as far as the Discovery Islands. The channel is not only navigable by vessels but also serves as the home for a very diverse array of marine life, from orcas and humpback whales to numerous fish species.

The town has a rich cultural history that is firmly rooted in the Indigenous people who have lived in the region for generations. The Kwakwaka'wakw First Nation can be felt in the area's totem poles, customs, and artwork, which cover the landscape. European settlers arrived thereafter, bringing with them industries like fishing and logging, which became staples in the economy of Port McNeill and have remained so to date. The oceanfront position of the town has rendered it popular with outdoor enthusiasts, who come here for deep-sea fishing, kayaking, and wildlife watching.

2. What is the status of coastal currents around Port McNeill?

Coastal currents around Port McNeill are determined by a complex interaction of many factors. Tides with their semi-diurnal cycle in the Northumberland Channel are a governing factor. Gravitational forces of the moon and sun cause large water-level fluctuations, resulting in strong tidal currents. During spring tides, the difference between high water level and low water level is extreme, resulting in very strong currents with velocities of several knots.

Regional prevailing winds, which are mostly from the west, also play a role. These prevailing winds can force surface waters, affecting the speed and direction of the coastal currents. Furthermore, the wide-scale circulation patterns of the North Pacific Ocean, for example, the Alaska Current, have long - extending effects on the hydrodynamics along the coast. Ocean eddies, generated from the mixing of different water masses, also introduce complexity to the coastal currents off Port McNeill. The shape of the coast and bathymetry of the seabed also influence the flow patterns because seabed features can direct or disperse the flow of the currents.

3. How to measure the coastal water flow of Port McNeill?

Surface Drifting Buoy Method

The surface drifting buoy method is one of the traditional methods of observing coastal water flow. Scientists release buoys on the ocean and track their trajectory with time. Tracking the position of the buoy at equally spaced intervals of time, they can find the direction and strength of surface currents. However, the technique can provide information only on conditions at the surface layer of the water column and is open to a high impact of interference by wind. The wind can push the buoys in a direction that does not align with the flow of the underlying currents, giving incorrect readings.

Moored Ship Method

The fixed ship serves as a platform to measure the currents in the moored ship method. Sensors are dropped from the ship to detect the water flow at varying depths. This method, even though it gives high-resolution vertical profiles of the currents, suffers from several limitations. Its geographical range is the area around a moored boat, and that the ship, by its mere presence, could disrupt the water's natural path, which, in turn, could affect accuracy. Keeping a boat moored for an extended period of time can also prove to be expensive and logistically inconvenient.

Acoustic Doppler Current Profiler (ADCP) Method

ADCP flow meter has evolved to become a higher-tech and powerful method of estimating coastal currents. It is able to measure water currents over a broad vertical range, providing accurate information about the velocity profile of the water column. ADCPs can be deployed on a number of platforms including ships, buoys, and the seafloor. Ship-mounted ADCPs can collect data continuously as the ship moves, surveying an enormous area in a relatively short time. Bottom - mounted ADCPs can provide long - term, fixed - point measurements, which allow researchers to study the long - term trends in the coastal currents.

4. How do ADCPs based on the Doppler principle work?

ADCPs work on the Doppler principle. They emit acoustic pulses into water. The pulses bounce off suspended particles in the water, such as sediment, plankton, or bubbles. When water is in motion, the frequency of the returned pulse changes. With this difference in frequency, the ADCP is able to calculate the velocity of the water relative to the instrument.

Most ADCPs consist of multiple transducer beams, typically four or more, that are angled in different directions. The multi - beam configuration makes it possible to measure the three - dimensional velocity of the water. By incorporating signals from these beams, the ADCP profiler can produce a full picture of the current velocity at a range of depths throughout the water column. The data acquired by the ADCP may either be computed on - line in real - time or recorded to be analyzed later, providing the user valuable information regarding the dynamic behavior of the coastal currents.

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

To enable accurate measurement of the coastal currents at Port McNeill, measurement gear should possess certain key properties. It should be made with rugged materials, be of small size, have low weight, consume low power, and be economical. Such characteristics enable large arrays of gear to be utilized so that the region can be covered in an overall spatial pattern.

Application of ADCPs having casings made of titanium alloy is highly recommended. Titanium alloy is highly acclaimed due to its very good corrosion resistance, which is very important in terms of deployment in the hostile marine environment. Titanium alloy avoids corrosion by resisting the corrosive action of sea water, precluding damage on the internal ADCP components. Titanium alloy is also strong but lightweight, promising durability and light portability to the instrument. This combination of properties allows long - term and accurate measurement of the coastal currents off Port McNeill.

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

Depending on Usage

The choice of ADCP depends on its usage. Ship - mounted ADCPs are ideal for ship - borne measurements. They are able to provide real - time data as the vessel moves in the water, covering a large space within a short duration. For stationary - point long - term observation, bottom - mounted ADCPs are more suitable. They are able to provide continuous data for a prolonged period, allowing the researchers to analyze the long - term trends within the coastal currents. Floating ADCPs are used to measure the displacement of water masses across large areas and are very useful in characterizing the large-scale circulation patterns.

Selection Based on Depth

The ADCP frequency also has to be considered in relation to the water depth. For depths of less than 70m, 600kHz ADCPs can be employed. They can detect high-resolution values in shallow waters. For a maximum depth of 110m, 300kHz ADCPs can be employed. For deeper depths, up to 1000m, 75kHz ADCPs are optimal.

There are some popular ADCP brands available in the market, including Teledyne RDI, Nortek, and Sontek. But for cost - effective users, the ADCP manufacturer China Sonar's PandaADCP comes with high recommendations. Constructed using pure titanium alloy, it provides good performance at an affordable price. It is a good option for users with limited budgets but who still need to use good ADCPs to measure coastal currents. You can learn more about them on their official website: https://china-sonar.com/.

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