Green Stormwater Infrastructure

Managing stormwater with natural drainage


Rainfall rushing off hard surfaces like roads and parking lots can overwhelm our piped drainage system and cause back-ups and combined sewer overflows. The runoff also carries pollution directly into creeks, lakes, and other waterways. Green stormwater infrastructure (GSI) prevents overflows and pollution much like a forest would-by slowing and cleaning the water, and either reusing it or allowing it to soak back through the soil. Examples of GSI include roadside bioretention swales and street trees that manage street runoff; raingardens and cisterns that manage roof runoff; and green roofs and permeable pavement that are self-managing.   


The City of Seattle recently released a DRAFT GSI implementation strategy to guide our work in managing polluted stormwater runoff with green approaches. In 2013, Seattle City Council Resolution 31459 challenged Seattle to rely on GSI to manage stormwater runoff wherever possible and set an aggressive target to manage 700 million gallons of stormwater runoff annually with GSI by the year 2025-a seven fold increase over Seattle's 2012 baseline. 


The draft Strategy sets an interim goal of managing 400 million gallons of stormwater runoff annually with GSI by the year 2020, summarizes progress to date, outlines a set of strategies and planned investments for accelerating the adoption of GSI in Seattle, and articulates a two-year work plan for City of Seattle departments. OSE is accepting public comment on the Strategy until August 26.  

Electronic public comment form 

For more information, contact Pam Emerson,  206.386.4145.