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Sediment Traps and Meanders Back in PEI Rivers

Sediment trap and a rock deflector new tools to improve wild Atlantic salmon habitat

Some rivers in the Cornwall, P.E.I., area have some new features this fall, designed to attract more wild Atlantic salmon.

The fish is in the process of being listed as a species of special concern on P.E.I., under the Species at Risk Act, because of damage that has been done to its habitat.

“The natural habitat would have been cobble, and it would have been rocky,” said Karalee McAskill, co-ordinator for the Cornwall and Area Watershed Group.

“There would have been lots of pools and riffles, places for them to eat, rest, find mates.

“Right now, what we have is a channel which used to be habitat, and it’s full of sand and fine silt. It smothers all of the food sources. It fills in all of the pools and the habitat, and you’re left with a barren area,” McAskill said.

“It’s basically like a 401 for fish. They can just fly through it, but there’s nothing really there that they can stop and call home.”

One of the projects is a sediment trap, newly constructed on Watts Creek, in the North River watershed.

McAskill said it will help get silt and fine sediment out of the water, making it better habitat.

“The rushing water that you get in the springtime after everything melts, it comes in with a load of sediment in it,” McAskill said.

“When it hits that sediment trap, it slows right down and then drops out all of that extra sediment. And then the clean water carries back through the main channel.”

Returning the meander

McAskill said there are other sediment traps being used by watershed groups across the Island, but the rock deflector is a new concept.

It’s made of large sandstone rocks, which will help restore some of the natural features of the river, where the salmon can live and breed.

“It’s deflecting the water around the rocks and in doing so it’s going to increase the velocity of the water, pick up the sediment and flush it downstream,” McAskill said.

“When it’s turning around the rock, it’s also creating kind of a meander. So it’s going to help that system, which is very straight right now,” McAskill said.

“It’s going to help the natural meander return over time, and it will also create pools on the downstream and opposite bank, and those pools will attract large fish.”

Recycled rocks

McAskill said what’s different about the deflector is that it’s installed without any wooden cribbing, or rebar, or the wire cages used for a gabion wall.

“It’s a standalone structure made of completely sandstone, and that way, as the years pass, there’s not going to be anything man-made left in the river, just a natural wearing of time,” McAskill said.

“The deflector will probably look different, but at least there won’t be any rebar or wood that people could get hurt on. ”

McAskill said it’s also unique that the large sandstone rocks were donated by the P.E.I. Department of Transportation, from the Cornwall bypass project.

“Sandstone is in high demand, everyone on this Island would love a big piece of sandstone like this. So I knew we were getting some gold.”

‘Historic issue’

Kris Hunter, of the Atlantic Salmon Federation, said the Cornwall projects are “fantastic” and fit in with other efforts to conserve and restore wild Atlantic salmon.

“Unfortunately, P.E.I., partly because of the geology and partly because of its history of its land use, has got a real big problem with sediment,” said Hunter, program director for Nova Scotia and Prince Edward Island.

“The idea of the trap is to deal with that historic issue of sediment.”

Hunter said he also likes that the rock deflector is using recycled rocks.

“That’s one of the other challenges on P.E.I. is we don’t have an abundant supply of gravel and boulders, which are often the tools that we use to build these in-stream structures,” Hunter said.

“It gets very costly to try and bring that in. They’ve decided to recycle some of these materials, and put them to new use.”

McAskill said the cost of the two projects was about $25,000, with another $10,000 in-kind from the provincial government and P.E.I. Watershed Alliance.

She said she’s also grateful to the landowners who allowed them to build the new structures on their properties.