Improving Habitat Along an Urban River
The Mallard Point side channel (also known as the Poplar Island side channel) is the longest side channel on the Bow River between Bearspaw and Carseland. The channel is located within Fish Creek Provincial Park in Calgary, Alberta. A combination of natural and human‐caused changes to the river have resulted in periods of high flows and low flows in the side channel. Flooding in 2013 re‐invigorated the side channel after a decade of very limited flows but exacerbated channel instability due to a lack of healthy streamside (riparian) vegetation.
Since the flood re‐activated the side channel so that it could now capture sufficient flows to support the local fish and wildlife, TUC’s goal of improving the health of this site moved to Phase 2 which included stabilizing the river bank at a key location to ultimately improve fish habitat and channel stability.
TUC decided to use bioengineering techniques to meet the goals of stabilizing the bank, and improving riparian health and fish habitat. Bioengineering is the use of natural and even living materials to achieve some engineering function. Before work could begin, the entire worksite along the river bank was isolated using large metal sheet piles. This allowed the construction crew to use heavy machinery on the river bank without causing water quality problems downstream. After the site was isolated, a fish rescue took place to remove fish from the construction area. For the next couple weeks, crews excavated eight trenches perpendicular to the river bank and installed three large root wad logs in each trench with the root end of the trees in water to provide cover for fish and also protect the bank from excess erosion.
In between and over top of each log structure, the bank was regraded to form terraces with the soil held in place with natural fibre “logs” along the bank. In between each soil wrap, over 2000 live willows were laid down to form “brush layers”. On the top of the bank, even more willows and poplars were planted to bring back some native woody plants that will ultimately help to provide more stability and enhanced habitat for years to come.
TUC will continue to monitor the site to ensure it is functioning as designed and conduct additional work such as weed pulls or tree planting as necessary. In the fall of 2015, the Bow River Chapter of TUC conducted a spawning survey within the side channel and counted a record number of Brown Trout redds. This will be repeated in the coming years.
Partners and Sponsors
This project was completed with the help of many partners and sponsors including the federal Department of Fisheries and Oceans’ Recreational Fisheries Conservation Partnership Program, Alberta Conservation Association, the Calgary Foundation, Shell Fueling Change, Enbridge, the 2013 National Fly Fishing Championships, CH2M Hill, Alberta Parks, the Friends of Fish Creek, BP Retirees, and the Bow River Chapter of TUC as well as many other volunteers. Project design was completed by Cascade Water Resources and construction was completed by Secure Energy Services.