What Stormwater Management Involves
We manage stormwater both at its source (pollution prevention) and through conventional infrastructure – or "conveyance" and "end-of-pipe treatment."
Source control
"Source control" means managing stormwater and preventing pollution where rain falls on individual lots or nearby in the neighbourhood, such as along public roads.
Examples of source control technologies or practices
- rain gardens (plants and soils are built to absorb and use water )
- green roofs
- permeable pavement
- rain barrels
- rainwater harvesting
- treatment system for the reuse of stormwater as an alternate source of water
How source-controlled stormwater is used
- for watering vegetation, flushing toilets or other uses
- it's infiltrated into the ground
- it's vaporized into the air by evaporation and plant transpiration (called "evapotranspiration")
- it's temporarily stored at source-control facilities before being released at a controlled rate
- it's quality-treated for other uses
Low Impact Development (LID) and Green Infrastructure (GI) are terms that describe landscape-based methods that infiltrate (absorb into the ground), evaporate (vaporize into the air) or transpire (taken up by vegetation which releases it to air) stormwater.
Conveyance and end-of-pipe treatment
Conveyance and end-of-pipe treatment are also referred to as a conventional infrastructure or system.
Examples of conveyance facilities include storm sewers and roadside ditches.
Examples of end-of-pipe treatment include stormwater ponds and constructed wetlands that are built to treat stormwater for quality prior to discharge to streams and lakes.
Municipal stormwater management systems are designed to handle small and frequent rain events. Currently, the urban stormwater from frequent storms is collected in municipal storm sewers and conveyed to nearby streams and lakes.
Municipalities may also build major drainage systems to manage excess urban overland flow for large, infrequent storms (for example, a large storm that has a one per cent chance of occurring in a year). A major drainage system like this may consist of public roads or land reserved along the path of the overland flow. It may also share components with municipal stormwater management systems, such as ponds that may be additionally designed for flood management.
