Buildings, roads, parking lots and other hard surfaces prevent rain from soaking into the ground. If stormwater that washes over these impervious surfaces isn't properly managed, it can carry pollutants into rivers and streams. Stormwater runoff can also cause flooding and erosion, destroy habitat and contribute to combined sewer overflows (CSOs). The City of Portland promotes projects that mimic natural systems and integrate stormwater into building and site development to reduce damage from urban stormwater runoff.
The natural system approach also helps replenish groundwater and restore healthy watershed function. The city often works with private property owners, school districts and non profit groups on projects that keep stormwater out of the sewer system. These partnerships let the community share in solutions that enhance the urban environment by viewing stormwater as a resource rather than a waste.
Portland is building sustainable street projects around the city to better manage stormwater runoff and enhance neighborhoods. Green streets include stormwater curb extensions landscaped with plants that filter pollutants from stormwater runoff, swales that infiltrate and store stormwater runoff, lowered planter boxes, permeable pavement and street trees.
Ecoroofs replace conventional roofing with a layer of foliage in a growing medium over a synthetic, waterproof membrane. Ecoroofs decrease stormwater runoff and insulate to save energy. They also absorb carbon dioxide, cool urban heat islands, filter air pollutants, add habitat for birds and insects and provide urban green space.
Innovative Wet Weather Demonstration Projects
From 2002 to 2009, the U.S. Environmental Protection Agency funded over 30 Innovative Wet Weather Program stormwater management projects that that demonstrate sustainable, low-impact stormwater management solutions. Rain gardens, swales and stormwater planters are examples of sustainable inflow control projects that help the city meet requirements to control CSOs.