In growing cities like Portland, problems arise from uncontrolled storm water runoff. Development and inadequate drainage systems increasingly compound problems associated with moderate to significant rainfall. Storm water runoff from these rainfall events accumulate in many areas of our city, causing nuisance flooding and possible threats to public health and safety.
In addition to drainage issues, the rain that falls on our streets, houses, driveways, parking lots, buildings and other impervious surfaces run off and carry pollutants such as oil, gasoline, pet waste and heavy metals. Storm water runoff from lawns and other green spaces can carry pesticides, herbicides and fertilizers. Over time, these pollutants accumulate in the waterways causing significant damage to our creeks, streams and lakes.
The EPA now considers pollution from all different sources, including urban storm water pollution, to be the most important source of contamination in the nations waters. Uncontrolled urban runoff also contributes to hydrologic and habitat modification, two important sources of river impairment identified by the EPA.