Over the past half century, urbanization has caused drastic changes to the hydrology and geomorphology of streams and rivers. The Serpentine River is a low-elevation, rain-dominant river located in the City of Surrey, British Columbia. Over the years, urbanization of the watershed, particularly in the upper reaches, has degraded what once was high quality spawning habitat for five salmonid species. The current project is an evaluation of previous restoration efforts at seven study sites and a restoration plan to effectively increase spawning habitat in the Upper Serpentine River. Grain size analysis of the study sites found up to 57% fine sediment in the subsurface particles, attributing to siltation rates of 1.2-1.6 kg/m2/day. Erodible grain sizes at the study sites ranged from 29-164 mm, which mostly exceeded the median size of spawning gravel. These results were verified with a tracer rock study, which together concluded that instream structures were required to reduce tractive forces and increase gravel retention.
Newbury weirs, or constructed riffles, were proposed as treatments because their hydraulic characteristics increase flow resistance, promote gravel retention, and create intergravel flows. Newbury weirs involve large diameter rocks spanning across the entire stream, causing accumulation of gravel on the upstream side and pool formation downstream side. Substrate scoured at the pool will be deposited at the tail end of the pool, creating spawning habitat in accelerating and downwelling waters. Bank stabilization using dense live staking with a protective rock toe key was prescribed to reduce further channel incision and siltation. In the longterm, watershed-level priorities including passage through the Serpentine sea dam, monitoring for urban contaminants, and installation of green infrastructure was recommended.
The proposed treatments are relatively inexpensive, and if successful, will reduce repeat addition of spawning gravel and increase salmonid production in the Serpentine River. However, the value of the current project extends beyond fish productivity estimates. Monitoring data from restoration works can be used to inform future urban stream restoration projects and contribute to the continual improvement of restoration techniques. The effects of restoration on not only sediment form (ie. gravel depth and size) but also processes (ie. sediment scour and fill) should be investigated in the field to verify theoretical models.
Urbanization of areas alters the natural hydrology of the land through the creation of impervious surfaces, removal of vegetation, and construction of storm sewer systems. These alterations impact physical processes and the biological communities of our waterways through the introduction of pollutants, creation of uncharacteristic hydrological regimes, and habitat loss and fragmentation. Integration of natural areas in our built environments will mitigate some of these effects and reduce the degradation of streams in urbanized watersheds.
Guichon Creek flows through an urbanized environment, which includes the British Columbia Institute of Technology (BCIT) Burnaby campus. A tributary flows into Guichon Creek at the south end of campus and the majority of its flow is from a stormwater sewer which receives runoff from the residential area east of campus. The tributary is approximately 150 metres and runs between a community garden and a small gravel parking lot before entering Guichon Creek.
This project proposes restoration of a 2,000 m2 parcel of land between Guichon Creek and the tributary. Restoration activities involve removal of an existing parking lot, management of invasive hybrid Japanese knotweed (Fallopia x bohemica) and Himalayan blackberry (Rubus armeniacus), creation of an off channel wetland, and addition of natural in-stream structures to the tributary. Wetlands provide important hydrological and ecological functions that will contribute to the restoration efforts on Guichon Creek. This wetland will improve hydrological functions of the Guichon Creek floodplain through increased groundwater infiltration, creation of a storage area, and pollutant filtration. Improving these functions is also an important component of making stream ecosystems more resilient to climate change. The wetland will also provide ecological benefits such as improved water quality and creation of amphibian habitat. This project focuses on the creation of habitat for northern red-legged frog (Rana aurora) and the Pacific chorus frog (Psuedacris regilla).
Another important component of restoration in an urban environment is creating a connection between people and the environment. Restoration of this space provides opportunities for public involvement and environmental education and awareness. This creates a forum to discuss the effects of urbanization on streams and show people where the runoff from their neighbourhood ends up. Forming that connection between people and their environment is an important step to creating interest and involvement in environmental issues.