Innovative Rainwater Management
Urban development can change a region's hydrology (water flow amounts and patterns). Where natural vegetation and soils allows the gradual absorption and slow movement of rain and snowmelt, paved streets and buildings speed both water and pollutants to our waterways. Pollutants from commercial, industrial and residential activities that may appear insignificant at their source are moved by rain and snowmelt into storm drains that flush the wastes into rivers, lakes, or marine waters.
Pollutants commonly include nutrients, sediments, pathogens and toxins.
- Toxins include copper from brake pads, zinc, cadmium, rubber from tires, lead and hydrocarbons.
- Contaminants accumulated during dry periods are picked up by the next rainfall and quickly moved to the drainage system.
First rainfall discharges can be the most dangerous, because "first flush" concentrations of toxins are high. When we build more hard surfaces like roofs, roads and parking lots, we also increase the volume of runoff. These higher flows flush with great energy into our waterways, scouring out essential habitat such as fish spawning and refuge areas, and eroding stream banks.
Rainwater Management Techniques Used in the CRD
Biorentention Ponds & Rain gardens
Planters, rain gardens, bioswales and biorentention ponds are depressed landscapes designed to collect, filter and sometimes convey or detain stormwater. Stormwater has time to drop out sediments and filter back into the ground, akin to the natural hydrological cycle.
Creek Restoration & Naturescaping
Native plants thrive in our climate and rainfall patterns. They rarely needing irrigation once established. They need little or no fertilizer or pesticide, which has benefits for stormwater quality. Restoring ditches and creeks or bringing them back out of pipes where they have been buried allows them to perform more naturally when it rains. Restoration even allows us to use some low lying riparian areas for flood storage once again.
The vegetation planted on a greenroof and the soil it grows in, absorb rain and reduce the amount of runoff leaving a building site. Greenroofs help insulate the buildings below, cool and cleanse the air, provide micro habitat for birds and insects, and provide attractive spaces for building users and nicer views for those who overlook the roofscape of a town.
Disconnected downspouts, permeable paving, underground cleansing systems, storage and rainwater harvesting and re-use are other techniques that reduce impacts on our aquatic ecosystems.
© Image courtesy of Ron Layters