Since the 1860s the watershed of Spanish Bank Creek has experienced many ecological disturbances due to extensive old-growth logging and urban development. Most notably, these disturbances have altered the vegetative composition and hydrology throughout the watershed. The historic old-growth forest has been replaced by species typical of earlier seral stages, as well as invasive species such as English ivy (Hedera helix). This disturbed vegetation mosaic is characterized by an arrested ecological trajectory that perpetuates degraded conditions. Urban development has eliminated over a third of the historic length of Spanish Bank Creek and storm drains were installed to direct residential drainage into the stream. The combination of a disturbed forest and degraded hydrology intensifies runoff and associated sediment transport, and decreases the hydraulic retention time of the watershed. This has led to a significant decline in abundance of chum, coho, and cutthroat salmonids in Spanish Bank Creek.
Previous research has established how trees partition precipitation into throughfall, stemflow, and interception, however there are few studies examining the effects of canopy closure on throughfall within the context of ecological restoration. Thus, the objective of this paper is to determine if increasing canopy closure can be used as a restoration model to decrease throughfall, and consequently increase the hydraulic retention time of the watershed. Results indicated that greater canopy closure was associated with decreased precipitation throughfall.
From these results I formulated a restoration goal and several treatments that would increase canopy closure, and also ameliorate the degraded vegetative composition and hydrology of the watershed. The restoration treatments prescribed in this paper constitute five years of physical enhancements from which self-sustaining biological processes will continue to restore ecosystem function and structure. Successful implementation of these restoration treatments will positively affect regional biota, as well as users of the Pacific Spirit Regional Park who come to recreate, learn, and connect.
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.