Mapping Lake Melville

Bonnie Learning
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Project will help shipping lanes, future projects

Dave Street (left) and Al Smickersgill are mapping the ocean floor of Lake Melville in central Labrador, updating the last set of surveys taken in the 1950s. The pair of hydrographers work for Canadian Hydrographic Services, and are based in St. John’s, but are working out of North West River until October.

It’s a beautiful day on the water in North West River, and Al Smickersgill and Dave Street are ready to tackle the day once again.

Smickersgill and Street are hydrographers with the Canadian Hydrographic Service (CHS), and are based in St. John’s.

But since June 16, the pair — along with skipper Mike Pope — have been mapping the ocean bottom of Lake Melville in central Labrador, which hasn’t been updated since the last surveys taken in the 1950s.

The 31-foot long hydrographic surveying launch “Pipit” leaves the public dock at North West River each morning (weather permitting) and heads out the bay.

When they get to a certain location, the boat stops so the hydrographers can release a probe into the water — which sends out over 1,000 individual beams — to determine the sound velocity.

“We do a sound velocity test each day, two to three times a day over different areas,” explained Street.

“Determining sound velocity is important as it helps to calculate the depth of the water.”

Street notes since the last hydrographic surveys were taken over 50 years ago, much has changed with the bottom of Lake Melville.

“There’s been a lot of silting from the rivers, river mouths have changed ... we are focused on getting accurate readings within five centimetres. It’s basically a picture of the bottom of the ocean floor.”

Smickersgill explained once the probe determines the sound velocity, the information is downloaded into their Global Positioning System (GPS) on-board the vessel, which then maps the bottom of the ocean floor.

He notes Lake Melville  — which measures approximately 80 miles long by 20 miles wide — has proven somewhat difficult to map.

“The size and shape of Lake Melville is so long and narrow, and there are so few places — such as islands — to take shelter if the weather gets unpredictable.”

While the pair’s goal is to map all of Lake Melville, their main priority is to map the shipping lanes running to the area.

“We’ve done work in the past in northern Labrador, for example, with regards to Voisey’s Bay and mapping fjords so that ships have an alternate route to use if need be.”

 

Publicly available

Smickersgill added the data collected from their work is available to anyone who may need it, including government departments, the fishing industry, and oil companies.

“It’s basically there for coastal marine management,” he said.

“Governments can use it for habitat managements, or fish stock assessment, oil companies can use it for determining laying of pipes, and so on.”

Street said some mapping work was carried out in Lake Melville in 2012-2013 through the University of British Columbia and Memorial University of Newfoundland.

“We’re basically picking up where they left off.”

Street said there are three vessels being used for the operation — the Pipit, the Plover and the Teal, with the first two using the Simrad Multi-Beam Sonar System, and the latter using the Interferometric Sonar System.

“Both systems give is 100 per cent coverage of the ocean bottom, and 100 per cent high resolution — there is no chance of missing anything, whereas years ago, it was just a profile, using sextons and single beam echo locators.”

Street explained they also collect data such as tide tables, currents, and water levels.

Once all the data is collected, he said, it would not only be used in the production of paper charts, but also two digital charts — the Raster Nautical Chart and the Electronic Nautical Chart.

“All the data will be corrected for tidal information and other factors,” said Street.

Both Street and Smickersgill are expecting to finish their work by October.

bonnie.learning@thelabradorian.ca

Organizations: CHS, Global Positioning System, University of British Columbia and Memorial University of Newfoundland Simrad Multi-Beam Sonar System Interferometric Sonar System

Geographic location: Lake Melville, North West River, Dave Street Labrador Northern Labrador

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