Sustainable Storm Water Management

Sustainable storm water management (SSWM) aims to collect, treat, infiltrate and or reuse rainwater as close as possible to the area where it falls and using natural systems. This Package considers stormwater as a valuable resource and tries to fully utilize it by controlling runoff where and when it is captured and making it available for use. The approach is based on the following principles [1]:

  • Reduce downstream flooding by attenuating runoff: reducing peak run-off rate and run-off volume (if possible).
  • Minimize the impact of development on water quality by using drainage systems that provide treatment benefits through natural processes
  • Providing integrated amenity, green space and biodiversity opportunities, and develop drainage designs that are sympathetic with the surrounding landscape character.
  • Ensure appropriate long term ownership, management and maintenance arrangements are in place.

Based on the above principles, this package focuses on two solutions that have different urban land use and ownership scopes. The first Solution contains guidance on integrated stormwater management planning at a city level, and on the coordination activities with other urban plans. It contains actions for developing Sustainable Urban Drainage Systems (SUDS) in public open spaces, such as markets, squares, and transport infrastructure such as road networks, pavements, highways, parking lots, transport terminals (bus, rail and air), etc. The second Solution focuses on actions for developing SUDS for residential, commercial and institutional buildings and facilities. It fits under the framework created by the first Solution, but it is complementary in the sense that it explores measures to enhance the intake of SUDS by the private sector.

Motivation / Relevance

Globally, cities are growing and with growth, the coverage of impervious areas is increasing. In Canadian cities, around 40% of the land use in a city consists of residential, commercial, institutional areas and 30-35% constitute of transport infrastructure [2]. These are the two major land use classes that consist of impervious surfaces and collect a large proportion of the rainfall in the city. Various studies show that, highly impervious area (75 to 100%) can increase urban runoff by approximately 50% [3] and if not captured are potential causes of waterlogging and floods in downstream areas.

Traditionally infrastructure planning in cities has often tended to dispose stormwater as rapidly as possible to avoid water logging and flooding that can adversely affect human health and cause damage to property. This approach is based on construction of vast stormwater channels and trunk sewer networks that combine stormwater with wastewater to be conveyed to a central treatment plant that often process huge quantities of wastewater which is finally discharged into downstream lakes, rivers or bays. The design, construction, operations and maintenance of such infrastructure is financially expensive, energy intensive and undermines the use of rain/storm water as a resource.

With the growing population in cities, the demand for water is also on the rise and the need to secure water resources for the future is becoming evident. If stormwater is collected, treated and infiltrated separately, it can be utilised as an additional water resource for the city. In doing so cities can increase water security, reduce costs for expensive infrastructure and reduce the potential risk of flooding. Additionally, creating a wetland system within the city to attenuate stormwater can improve carbon sequestration potential and provide additional recreational areas [4].

Main impacts

  • Reduce the flood risk in cities.
  • Contribute to increase local water resources
  • Abate the necessity for bulky capital investments for extension of water capture,
  • treatment, distribution bulk water transfer, etc.
  • Improving the aesthetic value of the city
  • Increase in property values in the city due to improved quality of life
  • Decrease the pressure on natural fresh water resources and ecosystems
  • Modulate temperature in the city and reduce the heat island effect
  • Improve urban biodiversity
  • Improve air quality

Benefits and Co-Benefits

  • Reduce the costs of treatment of wastewater
  • Reduction in the Local Government`s energy bill for wastewater treatment
  • Reduction in the energy consumption of buildings for cooling
  • Reduction in capital investments in expensive sewer networks
  • Reduction in per capita consumption of water (through reuse of stormwater)


Low hanging fruit
  • Storm water management in private lots and developments

    The solution aspires to deal with surface run-off at the point of which it occurs. This would be achieved by collecting, treating and infiltrating or reusing it where ever possible within the site or in the near vicinity using Sustainable Urban Drainage Systems (SUDS). Examples include using: decoupling of stormwater drains (from wastewater pipelines), green roofs, rain gardens, living walls, permeable pavements, rainwater retentions and reuse systems, and onsite infiltration systems. This solution is tailored to local governments that have the mandate to approve and enforce municipal building regulations or bylaws that require and/or incentivize the use of SUDS and rain water harvest in private buildings and facilities in the city. Learn More...

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  • Storm water retention and infiltration at city-scale

    This solution caters to local governments that have the mandate to manage stormwater in a city. It addresses the management of rainfall and runoff, especially, from public open spaces and transport infrastructure. The solution promotes the creation and enhancement of permeable surfaces, waterscapes and networks of open drainage channels and watercourses which slow down runoff and maximize infiltration and treatment by natural processes (e.g.: channels, swales, vegetated trenches, retention basins, wetland systems, multiple use green spaces, etc. Learn More...

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Additional Information