SEATTLE’S THORNTON CREEK, A BLUEPRINT FOR ENHANCING BIODIVERSITY THROUGH A SYSTEMS APPROACH: “You can restore the hyporheic zone. You can restore natural processes to the extent that we are actually attracting salmon to the site to spawn. I think there really is hope for the future,” stated Katherine Lynch, stream biologist with Seattle Public Utilities (May 2022)

Note to Reader

The April 2022 issue of Scientific American magazine featured Canadian-born stream biologist Katherine Lynch and her innovation in bringing nearly dead urban streams back to productive life in Seattle. A key takeaway from the article is that the stream is a system. It includes not just the water coursing between the banks but the earth, life and water around and under it.

In 2004, Katherine Lynch had an epiphany. Rebuilding a missing hyporheic zone in an urban stream became her mission. In the article, Erica Gies told the story of Lynch’s journey to restore Thornton Creek’s hyporheic zone. Lynch believed she could create a blueprint for enhancing biodiversity while also reducing urban flooding and drought.

Radical reconstruction in Seattle is bringing nearly dead urban streams back to productive life

“(Katherine) Lynch had been tracking discoveries about a layer of wet sediment, small stones and tiny creatures just below the streambed called the hyporheic zone,” wrote Erica Gies. “Stream water filters down into this dynamic layer, mixing with the groundwater pushing up. Water in the hyporheic zone flows downstream like the surface water above it but orders of magnitude more slowly.”

“Lynch realized that few people trying to restore Seattle’s streams were thinking about the hyporheic zone, or that the channelizing of streams scours it away, or that putting streams in pipes disconnects the zone from the stream water above.”


To read the complete article written by Erica Gies,  author of Water Always Wins: Thriving in an Age of Drought and Deluge, download a PDF copy of To Revive a River, Restore Its Liver.


A Stream is a System

“A stream is a system. What a simply expressed thought. And so obvious. Yet not well understood. The lack of understanding on the part of decision-makers and land use practitioners has had consequences that continue to ripple through time,” stated Kim Stephens, Executive Director with the Partnership for Water Sustainability in British Columbia.

Kim Stephens was the project manager and principal author of Stormwater Planning: A Guidebook for British Columbia, released by the government of British Columbia in 2002. The Guidebook was developed to support the rainwater management component of Liquid Waste Management Plans (LWMP) as required by the Province.

“In the 1990s, the work of Richard Horner, Chris May and others at the University of Washington was a source of inspiration for Guidebook development. They pioneered a systems approach which proved transformational in correlating changes on the landscape with impacts on stream system condition.”

“Horner and May examined the interaction of all the variables, defined four limiting factors, and established an order-of-priority for the factors. This is the road map for action to protect and/or restore system integrity.”

“Yet, a generation later, my observation is that practitioners in the local government setting seem unaware that there is a road map, let alone understand why and how a stream is a system. If the work of Katherine Lynch helps draw lasting attention to this core concept, then this would be a major win.”

Twin Pillars of Stream System Integrity

“In 2015, the road map for protecting stream system integrity led the Partnership for Water Sustainability to develop the twin pillars concept as a way to shine the spotlight on the fact that the stream is a system,” continued Kim Stephens.

“What we do on the landscape has consequences for the stream. This is commonly understood. Yet the impacts continue, decade after decade, in part because so few understand the concept of a system. The Partnership vision is to reconnect hydrology and stream ecology through local government asset management. This requires a paradigm-shift.”

‘In the world of local government asset management, the drainage service is the neglected service, and the cost of neglect grows over time. Thus, the Partnership appreciates what Katherine Lynch is doing in Seattle to connect dots. “

“She is literally drilling down into the streambed to reinforce the case for the systems approach. In 1996, Horner and May published their seminal findings. The top two factors are changes in hydrology and loss of riparian integrity. A generation later, Katherine’s work adds depth to our understanding of what is happening within the stream corridor.”

Asset Management Context 

“In 2015, the Ecological Accounting Process was an idea. The EAP methodology and metrics recognize the importance of the stream in the landscape. It has been a 6-year journey to test, refine and mainstream the EAP methodology and metrics through a building blocks program of applied research,” explained Kim Stephens.

“Water Balance Accounting, pillar number one, addresses changes on the land draining to the stream. Ecological Accounting, pillar number two, addresses changes within a stream corridor. Integration of the two is the goal.”

“Asset Management for Sustainable Service Delivery: A BC Framework provides local governments with an incentive to go down this path. The provincial expectation is that local governments would integrate ‘natural assets’ into asset management processes. EAP shows them how to do it for stream systems and water assets such as wetlands.”

“In  the 1990s, listing of Coho salmon as an endangered species in Puget Sound was a catalyst for cross-border collaboration between BC and Washington State. But people either  forget it, never knew it, or are just plain oblivious. Circa 2000, Rich Horner and Chris May inspired me and others to develop the Water Balance Methodology and this is the technical foundation for the Stormwater Guidebook.”

“Now it is 2022 and Katherine Lynch’s mission is to rebuild the hyporheic zone in urban streams. Her passion provides us with an opportunity to remind our audience why a stream is a system and all that means for moving from stopgap remediation to long-term restoration.”

To Learn More:

Download a PDF copy of “Living Water Smart in British Columbia: Natural asset management… cutting through the rhetoric”. Published by the Partnership in May 2022, the article addressed the question, what does “managing natural assets” actually mean in a municipal asset management context? Local governments need real numbers to deliver outcomes. The article described a path forward.