Rainwater Management

The traditional approach to drainage planning is to get rid of water as quickly as possible. This has led to erosion in streams and degradation of water quality. Coquitlam treats stormwater as a resource and manages rainwater to keep our watersheds healthy. Our rainwater management strategy helps to maintain base flows in streams, prevent erosion, improve water quality and protect fish habitat.  

The principle of the City’s strategy is to mimic the natural hydrology of a watershed by controlling and infiltrating urban runoff into the ground.

Rainwater Management Strategy Goals

  • Preserve the site characteristics, including natural terrain, drainage patterns, soil structure and native vegetation to the maximum extent possible;
  • Preserve the natural hydrologic cycle, including vegetative rainfall interception and evapotranspiration, and groundwater infiltration and percolation to the extent that subsurface conditions permit;
  • Mimic natural rainfall capture in areas of site disturbance; and 
  • Ensure the protection of property and public safely with the design of overflow capacity

Volume Reduction Targets

Coquitlam’s rainwater management target is to capture 75-90% of the average annual rainfall volume.  Together with water quality ponds for rainwater management, these measures will address run-off as well as water quality issues. Rainwater management is achieved through the use of source controls.

Source Controls

Source controls reduce the quantity and improve the quality of urban runoff at or near its source by using infrastructure or natural physical resources. Coquitlam requires source controls to be constructed at the time of new development in managed watersheds. Required measures are described in the table below.

Land Use Rainwater Source Control Measures
All single-family lots
  • 300 mm of topsoil in landscaped areas
  • Hard surfaces graded to landscape areas
  • Encourage the use of permeable paving material and rain barrels
Multi-family, Commercial, Institutional, Industrial
  • All of the above
  • On-site infiltration/retention trench or alternative measures
  • Designed to maximize stormwater volume reduction targets in applicable IWMP’s
City Roadways
  • 300 mm of topsoil in landscaped areas
  • Roadside surface swales in unobstructed boulevards, adjacent to parks and open spaces
  • Below grade retention trench in all other locations

Rainwater Source Controls

Roadside Swale

Roadside swales are shallow grassed or vegetated channels that capture, detain and treat road runoff and convey larger flows. The captured water is infiltrated to the ground to recharge the water table and provide base flows for streams. 

Roadside Swale

Rain Garden

Rain gardens are concave landscaped areas where runoff from roofs or paving is captured, treated and detained before being infiltrated into the soil below. Vegetation helps to filter out contaminants. Rain gardens are designed to have an aesthetic appeal as well as a stormwater function.

Rain Garden

Rain Barrel

Rain barrels collect rainwater that lands on your roof so that it can be used to water plants, lawns and gardens. Water that enters the ground rather than a storm pipe helps to maintain base flows in nearby creeks. Using a rain barrel also helps to conserve our drinking water supply by reducing the amount of tap water you use.

Rain Barrel

On –Site Infiltration Trench

On-site infiltration trenches collect the water from your perimeter drainage system and roof and return it to the ground rather than send it to a storm pipe.  The infiltrated water recharges the water table and provides base flows for streams. A slower return of water to the creeks reduces erosion and damage to aquatic habitat.

On Site Infiltration Trench

Roadside Infiltration Trench

Roadside infiltration trenches collect runoff from the road. The water is collected in an underground trench ground where it can be slowly infiltrated to the soil to recharge the water table and provide base flows for streams.

Roadside Infiltration Trench

Pervious paving

Pervious paving is a surface layer that allows rainfall to percolate into an underlying reservoir where it can be stored and slowly infiltrated to the ground. The surface can be porous asphalt or concrete, pavers, or grid structures.

Pervious Paving

Water Quality Ponds

The purpose of water quality treatment is to clean stormwater flows to an acceptable level for fish prior to discharge into receiving waters.  In order to meet water quality criteria, runoff from roadways, lanes, driveways, sidewalks and parking lots should be treated using rainwater management source controls.

Regional water quality ponds are used to make up for short falls in areas where source controls cannot fully meet the water quality treatment targets.

Standard drawings and specifications for the design and construction of source controls is available from the Development Services department.  Additional information for source control design is available in the Metro Vancouver Stormwater Source Control Design Guidelines report (May 2012, KWL).

Water Quality Pond

Engineering & Public Works Customer Service

Engineering Emergency Services for Water, Sewer and Roads

24 Hours a Day, 7 Days a Week

Phone: 604-927-3500

If this matter is urgent, please call our Engineering and Public Works Customer Service line at 604-927-3500 (24 Hours / 7 Days a Week).

Engineering Customer Service Email: epw@coquitlam.ca

Please Note - The Engineering and Public Works email address is only monitored during regular business hours (Monday to Friday:  8:00 a.m. - 5:00 p.m.).​