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Water Quality

Stormwater Runoff

Stormwater Runoff > Solutions > References and Links


Stormwater Runoff

Urban development can change the hydrology (water flow amounts and patterns) of an area to varying degrees. Where natural vegetation and soil structure once allowed the gradual absorption and slow through-put of rain and snowmelt, paved streets and buildings speed delivery of both water and pollutants to our waterways. Pollutants from commercial, industrial and residential activities that may appear insignificant at their source are transported by rain and snowmelt into storm drains that flush the wastes into rivers, lakes, or marine waters. These pollutants commonly include nutrients, sediments, pathogens and toxins. In developed areas, surface runoff is increased by changes in slope due to landscaping and increasing impermeable surface area of pavement and buildings. Contaminants accumulated during dry periods are picked up by the next rainfall and quickly moved to the drainage system. This is when discharges can be most dangerous, because "first flush" concentrations of toxins are high.

graph of streamflow and urban development

Change in streamflow with urban development (MELP [now WLAP] & MMA, 1994)


Many of us can contribute to polluted runoff in many ways, often without realizing it. Car washing and maintenance can release detergents, salts, anti-freeze, and oils onto the pavement and then into storm drains and ditches. Pollutants from vehicle exhaust and backyard burning eventually settle to the ground and are washed into adjacent waterbodies by the next rainfall. Wearing of disc brake pads can be a major source of copper in urban runoff. Households with lawns or gardens can use more chemicals on a given area than commercial growers. Half of all households with yards in British Columbia use fertilizers and one-quarter use pesticides. Excess amounts of these compounds find their way into the soil, ground water and adjacent surface waters.  
photo of polluted runoff


photo of warning sign "pollution"  

Industrial and commercial businesses also contribute to polluted stormwater runoff through accidental spills and leaks, and through use and discharge of potentially toxic compounds. Many industries are required by their liquid waste management permits to collect, monitor or treat stormwater. However, uncontrolled runoff from some industries remains a significant problem.

Highway stormwater runoff combines the worst of industrial and residential runoff in the variety and concentration of metals, particulates and petroleum compounds deposited by vehicles. Although stormwater runoff is generally more contaminated in urban areas, it also poses concerns in towns and rural areas, where erosion and sedimentation from roads, road-dust abatement chemicals and road salt contribute to pollution.


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Solutions

Watersheds are complex systems and the connection between human activities and the potential impacts on water quality are not always clear. The most effective and economic way to deal with NPS in an urban setting is to prevent the pollutants from reaching the water in the first place, rather than trying to remove them after-the-fact. Individually, people need to understand how their actions have the potential to contribute to NPS pollution. Once they know this, they can make decisions about changing the way they do things to minimize their impacts.
  photo of polluted stormwater runoff

Local planners, developers and elected officials also need to understand how their decisions can help prevent NPS pollution. In the past, stormwater has been considered a threat to property which should be removed quickly before flooding problems occur. In fact, stormwater is a valuable component of the water cycle and should be thought of as a resource rather than a liability. Stormwater can play an important role in recharging ground water supplies and maintaining stream base flows. However, it must be allowed to absorb into the ground rather than flow over impervious surface areas picking up the wastes of urban living on its way to streams, lakes and coastal areas.

Industry can address stormwater and other non-point sources of contamination by implementing pollution prevention plans for their operations.


Urban Design
Natural site features such as riparian corridors, streams, lakes, wetlands, surface depressions, soils and vegetation are integral to the hydrologic cycle. These features help to store, infiltrate, evaporate and cleanse stormwater runoff. Removal or modification of these features in conjunction with the increased impervious area associated with development causes adverse downstream impacts that include increased runoff flow rates and volumes, contamination of receiving waters, destruction of habitat and reduced ground water recharge. Preservation of key natural drainage and habitat features through careful planning can minimize the adverse impacts of development (GVSDD, 1999).

Buffer zones, setbacks and easements are approaches which can be used to protect the natural features discussed above. Buffer zones are strips of vegetation, either natural or planted, around water bodies. Such vegetated zones help reduce the impact of runoff by trapping sediment and sediment-bound pollutants, encouraging infiltration and slowing and spreading stormwater flows over a wide area. Setbacks are restrictions on development activities within a specified distance of a stream bank or other water resource. They can prevent or minimize erosion and gully formation, thus minimizing sedimentation and associated nutrient enrichment downstream. Easements are "green belts" around water ways which can be used to protect the water and also provide parks and recreational areas for residents. Easements may be negotiated with landowners and passed on to future owners as part of the deed to the property or purchased outright.

Reductions in impervious area can be undertaken by reducing the overall size of the developed area, and/or by reducing the amount of impervious surface created within the developed area. Disconnection of impervious surfaces can be undertaken by directing runoff from roofs and paved surfaces over vegetated surfaces before it reaches the drainage conveyance system.


Stormwater Treatment
The amount of a particular pollutant that can be removed from runoff depends on the nature of that pollutant. The removal of oil and grease from stormwater runoff may be accomplished by taking advantage of the fact that oil and grease will generally rise to the water surface under non-turbulent conditions; heavier sludges may sink under the same conditions. Some of the constituents typically found in urban runoff, such as lead and hydrocarbons, are largely associated with the suspended particulate fraction. Removal of suspended solids can therefore be expected to effect significant removals of other particulate-associated pollutants (e.g., lead and hydrocarbons) as well. The separation of suspended solids and associated pollutants from runoff waters may be achieved by using mechanical solid-liquid separation devices. Sediment particles can be removed by encouraging quiescent conditions, filtration or screening.

Many of the pollutants in runoff are associated with the smaller particle size fractions of the suspended solids, which are generally more difficult to remove by physical treatment processes than larger particulates. If sufficient time is allowed under suitable conditions, smaller particulates may aggregate to form larger particles in a process known as flocculation. However, many pollutants, such as nutrients, copper, zinc and cadmium often include a significant soluble component. Under certain conditions, soluble constituents may tend to condense and concentrate on the surface of solid particulates in a process known as adsorption.

  photo of stormdrain

A growing body of literature exists on biologically-enhanced methods of treatment for urban runoff. In addition to the physical removal of particulates through sedimentation and filtration, systems with a biological component can remove soluble pollutants such as oxygen-demanding substances, nutrients, metals and organic contaminants through uptake and transformation by aquatic plants and bacteria. Biologically-enhanced treatment systems for stormwater runoff include wet detention ponds, wetlands, biofilters (vegetated swales and filter strips), infiltration practices and urban forestry (MELP now WLAP], 1992). For more information on these systems and the physical removal processes described above, refer to the NPS Best Management Practices Compendium.


Residential Maintenance
There are a number of simple solutions we can incorporate into our day-to-day activities which will help protect stormwater quality:

Around your home:

  • Pave as little of your property as possible. Use gravel, interlocking stone or brick instead of concrete or asphalt.
  • Direct roof drains or gutter systems into rain barrels or over lawns (but not over onsite sewage systems) where bylaws allow — not to stormdrains or ditches.
  • Reduce your use of environmentally harmful cleaning products. Use alternatives such as baking soda, vinegar and hot water as drain cleaner or vinegar and water as an all-purpose cleaner.
  • Dispose of household hazardous wastes, such as paint, at collection or recycling depots; never dump them directly into storm drains.
  • If you have oil heating, regularly check your fuel storage tank for leaks and replace or repair the tank if necessary.
  • Drain your hot tub and swimming pool water slowly onto your lawn (but not onto your drainfield), not into storm drains. Where possible, dechlorinate the water before draining.
  • Sweep driveways and sidewalks instead of hosing them off.
  • Make sure your onsite sewage system is well maintained and meets your requirements; for more information click here.

Around your yard:

  • Collect pet wastes and bury them or flush them down the toilet (if you have an onsite sewage system, bury them away from the disposal field instead).
  • Reduce your use of fertilizers and pesticides. If you must use them follow instructions carefully and be careful using them near a waterbody.
  • Prune infested vegetation and use natural predators to keep pests in check. Pesticides can kill beneficial and desirable insects, such as ladybugs, as well as pests.
  • Compost yard and kitchen waste and use it to boost your garden's health as an alternative to chemical fertilizers.
  • Grow native plants in your garden - they require less water, fertilizer and pesticides.
  • Plant trees, shrubs and plants to slow water running off your property. This helps to prevent soil erosion and to increase water absorption.
  • Set your mower to cut only the top 1/3 of the grass. Your lawn will be healthier, absorb more rain and filter sediments.

Around your car:

  • Check your car's fuel, oil, brake, transmission, exhaust and cooling systems regularly. Fix leaks or problems immediately.
  • Use a dropcloth if you choose to fix it yourself.
  • Recycle used motor oil, antifreeze and batteries at collection centres.
  • Use phosphate-free biodegradable products to clean your car. Wash your car over gravel or grassy area, but not over an onsite sewage system. Go to a car wash if necessary.
  • Use your car less often. Walk, bike, carpool or take public transit.



photo of Cecelia Creek sign   Education
Concerted efforts to educate ourselves on how to prevent non-point source pollution is probably the most important aspect of addressing the issue. To effectively reduce our impact requires a fundamental change in attitude and behavior on a day-to-day basis. Many people fail to make the connection between the fluid leaking from their automobile, the stormdrain and the stream it eventually discharges to. They don't understand that septic systems which go unserviced will eventually fail and pathogens and nutrients will leach into nearby waterbodies, which may also be their source of drinking water. In an effort to have greener, healthier lawns and gardens many home owners over-apply fertilizers and pesticides — much of which is washed away with the next rainfall. These are simple examples but they illustrate the point — our everyday activities have the potential to impact our water resources.

Education programs need to be focussed on a target audience and often the most receptive audiences are school aged children. By exposing them to the fundamentals of environmental protection at an early age, we can instill a sense of awareness and responsibility, with respect to water and other natural resources, that will stay with them throughout their lives. Under the provincial Eco Education Program, the Water Crew visits intermediate grade classrooms (four to seven) and uses a combination of activities and interactive demonstrations to help the students identify human impacts on water and generate solutions to help protect water resources. Many other NPS education efforts are being initiated throughout the province by government agencies at all levels as well as community stewardship groups focusing on specific local issues.

photo of Water Crew presentation to elementary school children

Water Crew presentation to elementary school children

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References and Links

Best Management Practices Guide for Stormwater. 1999. Greater Vancouver Sewerage and Drainage District.

Community Greenways: Linking Communities to Country, and People to Nature. 1995. The Stewardship Series. Province of British Columbia and Department of Fisheries and Oceans.

Environmental Best Management Practices for Urban and Rural Land Development in British Columbia. 2004. British Columbia Ministry of Water, Land and Air Protection, Vancouver Island Region.

Land Development Guidelines for the Protection of Aquatic Habitat (PDF: 129 pages). 1992. Province of British Columbia and Department of Fisheries and Oceans.

Stormwater Planning: A Guidebook for British Columbia

Stream Stewardship: A Guide For Planners and Developers. 1993/94. The Stewardship Series. Province of British Columbia and Department of Fisheries and Oceans.

Tackling Non-Point Source Water Pollution in British Columbia: An Action Plan. 1999. Ministry of Environment, Lands and Parks (now, Ministry of Water, Land and Air Protection).

Urban Runoff Quality Control Guidelines for British Columbia (PDF: 6.03 MB / 138 pages). 1992. Ministry of Environment, Lands and Parks (now, Ministry of Water, Land and Air Protection).

 


Updated: May 2005


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