Most of this creek was buried underground a century ago. What remains runs through Ravenna and Cowen Parks - a living reminder of what Seattle's watersheds used to look like. Every bioswale helps bring it back.
Serving the Ravenna Creek Watershed since 2026
Free AssessmentRavenna Creek is a story of what happens when a city forgets its water.
Ravenna Creek once flowed from Green Lake all the way to Lake Washington through Union Bay. It was a natural drainage corridor for the entire central-north part of Seattle.
Then the city lowered Green Lake by seven feet in 1911 and Lake Washington by nine feet in 1916. The creek lost its upstream source. Most of it was diverted into storm drains. Today, only 3,500 feet of open creek remain, running entirely through Ravenna and Cowen Parks.
The water that feeds it now comes from a small wetland in Cowen Park - and from the runoff of every yard, roof, and street in the surrounding neighborhoods. That's where bioswales come in.
Understanding what was lost helps us understand what can be rebuilt.
Ravenna Creek flowed freely from Green Lake southeast through a forested ravine to Union Bay on Lake Washington. The Duwamish people knew these waters long before the city existed.
The city lowered Green Lake by seven feet to create more parkland. This severed the creek's primary upstream water source, beginning the process of turning a living creek into a storm drain.
The Ship Canal project lowered Lake Washington by nine feet. The creek's downstream connection changed permanently. Most of the lower reach was piped underground.
Surrounding neighborhoods densified. Impervious surfaces increased. The creek that remained became increasingly dependent on stormwater runoff - often polluted - for its flow.
We can't undo a century of development. But we can change what goes into the creek. Every bioswale in the Ravenna Creek watershed filters pollutants and slows runoff before it reaches the last 3,500 feet of open water.
In a watershed with no natural headwater, your yard's runoff is the creek's water supply. Make it clean.
Seven-layer bioretention removes pollutants from your runoff before it enters the storm system that feeds Ravenna Creek. Clean water in, healthy creek out.
Bioswales absorb up to 90% of your stormwater on-site, reducing the sudden surges that erode the creek bed and overwhelm its capacity during storms.
Native plants, engineered soil, and natural hydrology. Your bioswale doesn't just manage water - it recreates a small piece of the watershed that was paved over.
Every neighborhood in the Ravenna Creek drainage area.
Home to the daylighted creek. The heart of this watershed's story.
Family neighborhood east of Ravenna Park. Established homes, mature lots.
The creek's lost headwater. What Green Lake can't drain, your yard can.
Southern edge of the watershed. Dense, impervious, high-impact bioswale territory.
Only 3,500 feet of Ravenna Creek still flows in the open. Every bioswale in this watershed sends cleaner water to those last visible stretches - and makes the case for uncovering more.
Seattle's largest urban watershed - 12 square miles, 10+ neighborhoods
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