Stormwater begins as rainfall and melting snow/ice. Stormwater on the ground is called runoff. In undeveloped areas, runoff will either soak into the soil, get absorbed by plants, evaporate or find its way to the nearest body of water.
In developed areas, hard surfaces like roads, roofs, driveways and parking lots prevent water from seeping into the ground. Instead, stormwater runoff flows to catch basins while picking up contaminants like motor oil, animal waste and cigarette butts along the way. Storm sewers carry the dirty water to stormwater outlets draining to creeks, streams and rivers. During a big storm, storm sewers can get overloaded and contribute to flooding.
Stormwater management reduces the risks caused by uncontrolled runoff. Municipal infrastructure like stormwater ponds temporarily hold water back. These man-made ponds collect runoff and slow down the flow. Dirt and other pollutants can settle and be broken down by plants and bacteria. Cleaner water leaves the ponds at a controlled rate, and there is less danger of flooding and erosion downstream.
In suburban and rural communities, stormwater ponds blend into the landscape. Some look like natural lakes and are a habitat for fish, ducks and birds. Others are designed to be dry most of the time; they simply look like a depression in a park or field. During a storm, they will fill up with rainwater to relieve the downstream drainage system. Other ways to manage stormwater are, for example, rain gardens, oil and grit separators, underground storage tanks, culverts and roadside ditches.
All residents, properties and businesses in Ottawa benefit from stormwater management. It keeps streets and basements dry, local waterways healthy and our drinking water sources clean. The City of Ottawa operates and maintains:
- More than 2,700 km of storm sewers
- 111,000 catch basins
- 1,600 stormwater outlets
- 133 wet ponds
- 100 dry ponds
- 83 underground facilities
- 12 stormwater pumping stations
- 1,200 km of municipal drains in rural areas
- More more than 6,000 culverts, mostly in rural areas