Stormwater runoff occurs when precipitation from rain or snowmelt flows over the ground. Impervious surfaces like driveways, sidewalks, and streets prevent stormwater from naturally soaking into the ground.
Stormwater can pick up debris, chemicals, dirt, and other pollutants and flow into a storm sewer system or directly to a lake, stream, river, or wetland. Anything that enters a storm sewer system is discharged untreated into the water bodies we use for swimming, fishing, and providing drinking water. Polluted stormwater runoff can have many adverse effects on plants, fish, animals, and people.
On-site retention and infiltration of stormwater using best management practices such as rain gardens, pervious pavement, and rain barrels decreases the surge of water to rivers and streams after rain events. These practices can reduce flooding in rivers and streams. To learn more about Polk County’s flood control program, visit the Be Flood Smart! web page.
Polk County administers a Stormwater Management Program (SWMP) that has been created for the area of Polk County located within the City of Salem urban growth boundary (UGB). This program was developed to meet the Municipal Separate Storm Sewer System (MS4) permit requirements of the National Pollutant Discharge Elimination System (NPDES), and is reviewed and updated annually. Polk County also implements a Total Maximum Daily Load (TMDL) Implementation Plan. The TMDL Implementation Plan is designed to reduce river and stream temperatures as well as the levels of bacteria and mercury that enter County rivers and streams. The TMDL Implementation Plan applies county wide. If you would like to learn more about Polk County’s SWMP or TMDL Implementation Plan, please contact Polk County Community Development at (503) 623-9237.
Roof tops, parking lots, and driveways create impervious surfaces that concentrate stormwater run-off. Stormwater flowing over these developments pick up oil and other particle matter that can be harmful to riparian ecosystems. In order to decrease the quantity and increase the quality of stormwater that enters the County rivers and streams, construction operators should plan how to minimize stormwater runoff from new development prior to beginning construction. The following links provide technical guidance in implementing practices that can be used to minimize the impact of development on County rivers and streams:
Trees and other vegetation provide stream bank stability and minimize erosion caused by rain events. Streamside vegetation shades the stream itself, thereby acting to reduce stream temperatures, and provides a natural filter for sediment that becomes suspended in stormwater.
Online training courses are available through the EPA website.