Stormwater

What is stormwater?
Willamette River Water TrailStormwater is runoff from rain and snowmelt which flows over the ground, driveways, streets, parking lots, and buildings that drains to streams, rivers, lakes, and the ocean.

Why should we be concerned with stormwater?
There are two main issues relating to stormwater runoff; one is the volume and intensity of the runoff water and the other relates to the potential contaminants that the water is carrying to a storm drain, lake, stream, wetland, or river.

What is stormwater management?
Stormwater management addresses delaying, retaining, treating, or infiltrating stormwater runoff. The loss of wetland and floodplain areas along with the corresponding increase in impervious surfaces necessitates the active management of stormwater runoff through the use of structural controls, such as water quality facilities and detention ponds, or other management measures within most urbanized areas, including privately owned systems. For helpful information about maintaining your stormwater system please refer to: (A Guide to the Stormwater Maintenance & Access Easement, A Manual for the Operation & Maintenance of Privately Owned Stormwater Facilities, and Stormwater Annual Inspection and Maintenance Report) owned systems.

Structural controls provide a means to manage the amount, intensity and contaminants contained within stormwater runoff. However, it is difficult to construct and operate a stormwater facility that will work as effectively as the natural system functioned prior to urbanization. Other measures that should be considered include, but are not limited to: restoring wetlands and floodplains, increasing the amount of typical and urban forest or native cover, reducing the amount of impervious cover, and minimizing our collective impact (e.g. responsible home and work practices) on any given watershed.

What is stormwater management?
Stormwater management addresses delaying, retaining, treating, or infiltrating stormwater runoff. The loss of wetland and floodplain areas along with the corresponding increase in impervious surfaces necessitates the active management of stormwater runoff through the use of structural controls, such as water quality facilities and detention ponds, or other management measures within most urbanized areas, including privately owned systems.

What is Low Impact Development?
Structural ControlsLow impact development (LID) is a comprehensive approach to engineering design and stormwater management. LID aims to replicate the pre-development hydrologic regime of watersheds through infiltrating, filtering, storing, evaporating and detaining runoff close to its source. LID incorporates a strategic plan into development that mitigates our impact on the environment while maintaining a diverse habitat for the community and wildlife.


How is the City managing stormwater?
Street and SidewalkThe Natural Resources Program works cooperatively with other city departments to plan and manage the drainage system in Wilsonville. The federal Clean Water Act, Safe Drinking Water Act, and Endangered Species Act direct the City to improve stormwater quality and protect watersheds, rivers, streams and drinking water resources.


Key Elements
Key elements of the city’s stormwater management program include:
  • 2012 Stormwater Master Plan - The 2012 Stormwater Master Plan identifies areas of the city that currently experience erosion, flooding, and water quality problems, or that can be expected to experience such problems with future development.
  • Public Works Standards (Section 3) - Public Works Standards (Section 3), outlines design and construction requirements for stormwater and surface water management. Provisions are intended to prevent or reduce adverse impacts to the drainage system and water resources. These requirements are intended to protect the beneficial uses, such as swimming, fishing etc., in the Willamette River.
  • 2012 National Pollutant Discharge Elimination System Permit - The federal Clean Water Act requires municipalities to obtain a National Pollutant Discharge Elimination System (NPDES) permit for stormwater discharges. View additional permit information.
  • 2012 Stormwater Management Plan - The city’s Stormwater Management Plan (SWMP) is the means for complying with the NPDES permit and managing the city's stormwater system. All stormwater facilities on private property are maintained by the property owner or Home Owners Association.
  • Total Maximum Daily Loads (TMDLs) - Total Maximum Daily Loads define the amount of pollutants that can be present in a water body without causing water quality criteria to be exceeded. Extensive water quality monitoring and modeling (for temperature, bacteria, and mercury) has been completed to establish Total Maximum Daily Loads for the Willamette River. The City’s March 2008 Willamette River TMDL Implementation Plan was approved by the Oregon Department of Environmental Quality (DEQ). On August 31, 2014 the City submitted its updated TMDL Implementation Plan to the DEQ.
  • Erosion Control Program - Wilsonville recognizes the importance of protecting the environment and providing for the long-term stewardship of our natural resources. The Natural Resources Program has responsibility for managing the Erosion Control Program.
PondAdditional Information
For helpful information about maintaining your stormwater system please refer to the following:
To report a clogged stormwater catch basin or pipe, contact Public Works at 503-682-4092 or fill out our online request form.