Colwood Creek Watershed
The expanding human developments in the Colwood Creek watershed have created several interrelated concerns for the ecosystems in the area. Nevertheless, functional ecosystems and human use do not have to be mutually exclusive, if steps are taken to develop sustainably.
As more buildings and roads have been constructed, a greater area of land in the watershed has been transformed into impervious surfaces. Unlike forested land, which acts as a sponge to soak up rainwater, pavement, asphalt and roofs shed water. Rainwater then flows into storm drains that discharge into local creeks and into Esquimalt Lagoon, often carrying with it harmful chemicals such as automobile fluids. This pollution, along with pesticides and fertilizers washed off lawns and gardens, and sewage from malfunctioning septic systems, can be toxic to aquatic organisms and wildlife such as birds that feed upon them. Esquimalt Lagoon has limited tidal flushing, since it is only connected to the ocean through a narrow opening, therefore these substances can accumulate in the lagoon. Impervious surfaces are common in the mid portion of the watershed; Colwood Ck. is located among the shrubs on the left of the frame (photo: L. Townsend)
The problem of impervious surfaces is also associated with habitat loss and degradation and stream channel degradation. As riparian zones are cleared and replaced with urban structures and manicured landscaping, the soil is less able to store excess rainwater. This excess then rushes into streams and may cause erosion, particularly in streams whose channels have been excavated and cleared of wood debris; unlike human-made ditches, natural channels have features such as intact riparian vegetation, large woody material and meanders that help to dissipate the energy of high flows.
Another way in which stream channels and habitat have been degraded is through trampling of riparian zones. This problem is particularly noticeable in the otherwise relatively healthy forested area in the lower reaches of Colwood Creek. Here, walking trails are situated too close to the stream, where they create the potential for erosion and sedimentation, and prevent healthy riparian vegetation from growing (see photo below). A walking trail situated too close to Colwood Creek, on Royal Roads University property, causes trampling of riparian vegetation and erosion (photo: L. Townsend)
The solution to many of these problems lies in developing prudently and using sustainable technologies. For example (and see How can I help for links to more information):
- new developments can be concentrated in already-disturbed areas
- sensitive ecosystems and riparian zones can be protected with conservation covenants
- recreation areas can be designed to allow public enjoyment of natural areas but minimize impacts, for example with careful trail design and designated viewing platforms
- new developments can be laid out to minimize sprawl and maximize greenspace
- road widths can be minimized in residential developments
- pervious alternatives to asphalt and pavement can be used for sidewalks, parking lots and roads
- rainwater that washes of impervious surfaces can be captured, stored and released slowly into the ground, with techniques such as vegetated swales, rain gardens and constructed wetlands
- green roofs can be used to intercept rainwater falling on roofs, to nourish plants and potentially for reuse such as for flushing toilets