Size: 1 km | Completion: 2015
During the course of a site development project, WalterFedy’s water resources team identified that the existing floodplain was not functioning effectively. Our client, Birdland Developments, also expressed a desire to enhance the natural habitat of the corridor and to incorporate a connecting section to the existing community multi-use trail network. This presented an opportunity to enhance the existing agricultural drainage ditch to create a healthy stream with a hydraulically connected floodplain.
To achieve these goals, our water resources team recommended a natural channel design with a natural cross-section, widening the overbank flow area and adding a meander, pools and riffles, and offline pools. The design was then developed in close coordination with the owner, the Grand River Conservation Authority, GSP Group, and LGL Limited. The solutions created by this design improve the quality of the terrestrial and aquatic habitats while providing an attractive feature for the community.
Improving Water Quality
In addition to enhancing the aesthetics of the stream, adding a meander increases the movement of the water. As the water travels down the stream, it continuously moves, squeezing and relaxing within the confines of the channel itself. Adding pools and riffles contributes to this movement, as the water has to change direction as it sinks into the pools and flows over the riffles. This vertical and horizontal movement also means the water has to travel further, expending more energy in the process. In water, energy presents as heat, so expending more energy means losing more heat. This cooling is furthered by the rocks placed in each riffle, causing the water to foam and bubble, introducing more air into the water and causing evaporation. As with movement, evaporation expends energy and heat. At the same time, the dissolved oxygen content in the water is enriched.
Offline pools were introduced to act as natural sediment traps in addition to providing a habitat for birds, frogs, and other wildlife. These pools capture sediment and debris from surface runoff, rainfall, or when the water level rises, improving water quality in the stream. When the water from the offline pools does eventually drain back into the stream, it percolates through the soil which acts as a natural filter.
By changing the path of the stream, introducing pools and riffles, and adding offline pools, the water flowing from the warmer stormwater pond upstream is cooler, cleaner, and enriched with oxygen as it flows through the reach, creating a desirable habitat for fish and other aquatic species.
Creating a Healthy Ecosystem
Compared to the former narrow, shallow drainage ditch, the enhanced stream and functioning floodplain provide an opportunity for a variety of plant species to grow. Different plants require different wetness conditions, which are difficult to achieve in a drainage ditch with little water that does not promote movement. The variation in stream depth and presence of a functioning floodplain, as well as the improved water quality, increases the diversity of plant species in the stream and along the banks. This provides erosion control, energy dissipation, sediment capture, and creates an attractive environment for pedestrians on the adjacent path, which was also constructed as part of this project. Plant life diversity also promotes animal diversity, offering food and creating a migratory pathway for animals that can travel north to south with coverage from plant life.
Through close coordination with our client and continuous consultation with the local authorities and our broader project team, we were able to introduce a new feature that mitigated project challenges and benefited the environment and the community.