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An environmental assessment has put forward seven options to secure the quickly eroding land along the Carp River near the Fitzroy Harbour Community Centre (FHCC).
The City of Ottawa hosted an open house at the FHCC on Oct. 26 to present their options to the public and gather feedback.
About eight metres of land has been washed away from 1999-2008 along a 175-metre strip of the river, and only about one more metre can be lost before affecting the outdoor hockey rink along the edge of the Carp River near the community centre.
Project manager Kevin Cover said that he first came out to observe the river in July, and the EA has progressed quickly since then to deal with the issue.
“Erosion is a natural process,” Cover said. “We need erosion. But when it becomes a safety risk, that’s when it becomes a problem.”
Over the past decade, the river began to flow along a different, lower route that cuts along the shoreline and eats away at the land. What used to be a slope leading down to the water has now become a cliff.
“You wouldn’t want to be standing on the edge of it in the middle of the summer,” Cover said, when the water level is at its highest.
Cover and his team have proposed seven possible options. The one that looks most promising, said Cover, involves a partial river channel retraining, to reroute the water back to the way it originally flowed.
Doing so would involve filling in the lower ground where the water is now flowing from, providing a blockade to reroute the river.
While it would be a fairly expensive solution, it would do minimal damage to the riverside and would cut down on erosion significantly.
“Basically, we’d be redirecting the water and putting it back where it should go,” Cover said.
Karen Taylor is president of the FHCC, and said that she’s glad the problem is being dealt with.
“It’s been slowly eroding for a number of years now,” she said in an interview this summer. “They finally had to do something about it because it’s getting out of hand.”
Public input and comments will be incorporated into the final solution. A detailed study will be released at the end of November, followed by a 30-day review period where community members can still offer feedback.
The final design will be drafted sometime during the winter of 2012, and construction should begin in the summer of 2012.
To submit feedback or learn more about the EA process, contact Kevin Cover at 613-580-2424, ext. 22830 or e-mail him at kevin.cover@ottawa.ca.
SEVEN OPTIONS:
Option 1: Do nothing. The riverbank would continue to experience the natural process of erosion, but this alternative would not reduce the loss of land or improve public safety.
Option 2: Re-grade and re-vegetate the slope. Workers would decrease the riverbank slope by cutting out a portion of the top and using it to fill in the base. The bank would be re-vegetated by adding layers of brush, which would also protect against erosion.
Option 3: Reconstruct and rip rap the stream bank. Rip rap are basically lots of little rocks which would be placed along the base of the riverbank to protect the land and improve its stability. This option also includes re-vegetating the top of the riverbank with grasses, shrubs and trees.
Option 4: Create a gabion basket retaining wall. The gabian basket technique uses steel wire mesh to create cages filled with rocks, which are used to support the base of the riverbank. Cover said that the gabion baskets will rust over time and need to be replaced, making the maintenance fee of this alternative fairly high. The top of the riverbank would be re-vegetated and flattened also.
Option 5: Re-grade the slope and add rock deflectors. These deflectors would be rock groynes, or a pile of rocks placed at the base of the eroded riverbank. They would stick out like docks and reduce the speed of the water along the eroding land. As Cover put it, “They’re speed bumps for water.” In this alternative, the riverbank would also be flattened and re-vegetated with grasses, shrubs and trees. Over time, the area between the groynes would accumulate sediment and plant material, further deflecting the flow of the river.
Option 6: Partial river channel retraining. Workers would fill in the area where the river is now flowing, and divert it back to its previous streamline. The strip of land installed to divert the water is called a “fill terrace,” and it would be lined with large rocks. Cover said that in his professional opinion, this is the best option to solve the Carp River erosion issue.
Option 7: Full river channel retraining. The most extreme alternative of the bunch, this option would see the bedrock blasted out beneath the desired river path to make it deeper and easier to cross. The current river flow region would be filled in to block water from entering and causing more erosion. This option would be the most costly.
All options include the rebuilding of bars along the river – like sand bars, but with deposited materials – that had previously been built but have moved around as the river flow changed. These bars will be moved to unblock certain areas and help to redirect the water flow in the desired direction.
View article and photos here.