The stability of a streambank is influenced by soil, groundwater and vegetation. Healthy, intact vegetation near streams helps reduce landslides and erosion which can negatively impact stream health. A well-vegetated riparian ecosystem can trap and store sediment and organic matter. 

Vegetation near streams provides shade which impacts stream temperature. The temperature of a stream affects the survival and productivity of aquatic species. Cool water is ideal for fish survival, growth and productivity. Reducing shade near a stream increases stream temperature.

Wood plays an important role in stream morphology (width, depth and size). Woody debris create dam pools, plunge pools, riffles, glides, undercut banks, and side channels. Different species need these different mini habitats in a stream. The wood debris changes stream velocity, traps sediment, alters stream course, and stabilizes banks. This creates complex and diverse stream environments which improve aquatic species health.

Organic matter from riparian ecosystems makes its way to streams via litter fall (leaves, moss, twigs etc.). Essential nutrients enter streams this way. These nutrients are consumed by species further down the food chain like microbes and invertebrates that are eaten by fish.

Riparian areas remove pollutants from runoff. A well-vegetated riparian ecosystem can remove excess nutrients, metals and pesticides before water enters the stream.

Background: The City is required to update its critical areas ordinance (CAO) to comply with Best Available Science (BAS). These amendments will be completed by using Washington State Department of Fish and Wildlife (WDFW) guidance documents Riparian Ecosystems, Volume 1: Science Synthesis and Management Implications and Riparian Ecosystems, Volume 2: Management Recommendations as a source for BAS developed to support local jurisdictions designate and protect riparian ecosystems as critical areas. The amendments are also required to complete the periodic update of the CAO mandated by the Washington State Department of Commerce Growth Management Services Unit (Commerce).

Staff anticipate a complete review of critical area regulations and shoreline regulations in 2027-2029. The State mandates that the Shoreline Master Program is updated every ten years, next due June 30, 2029.

WDFW recommends riparian management zones in Kenmore extend 200 feet from either side of a stream.

Key Policy Questions for City Council Consideration: The following questions are intended to guide discussion and decision-making on preferred policy direction and next steps.

GMA & Growth Targets

• How would each stream buffer option affect Kenmore’s ability to meet GMA-mandated housing and job targets through 2044?
• Would expanding stream buffers significantly reduce the City’s developable land capacity identified in the Comprehensive Plan?
• How should the City balance the Growth Management Act’s growth requirements with its environmental stewardship goals?

Environmental Protection/Regulatory Flexibility

• What level of ecological improvement does the City want to achieve relative to the land area encumbered by new buffer widths?
• How many additional parcels and acres would be impacted under each option, and are there mitigation or incentive tools to offset those impacts?
• Should the City establish differentiated standards for developed versus undeveloped parcels to minimize redevelopment constraints?
• Should existing flexibility tools (variances, buffer averaging, reasonable use exceptions) be expanded to accommodate redevelopment within constrained parcels?

What are the different types of streams and what are the current setbacks?

The Buffer Comparison table below summarizes the proposed buffer width options (low, medium, high) compared to existing buffer widths. 

Buffer Comparison Table (by Water Types)

Water Type	Stream Type	Existing Buffer Width (feet)	Proposed Buffer	Difference (feet)
Type S (Shoreline)	Lower portion of Swamp Creek, Sammamish River, Lake Washington	See KMC 16.65.020	See KMC 16.65.020 (no change)	See 16.65.020 (no change)
Type F (Fish bearing-salmonid)	Other water bodies used by or containing habitat suitable for salmonid fish	150 – Little Swamp Ck. 100 – all others	Low – 150 Medium – 200 High – 100 min to 231 max (RMZ)	L = +50 M = +100 H = Varies based on RMZ
Type F (Fish bearing-non-salmonid)	Other water bodies used by or containing habitat not suitable for salmonid fish	50	Low – 150 Medium – 200 High – 100 min to 231 max (RMZ)	L = +50 M = +150 H = Varies based on RMZ
Type N (Np and Ns)	Perennial or seasonal non-fish bearing streams	25	Low – 100 Medium – 100 High – 100 min to 231 max (RMZ)	L = +75 M = +75 H = Varies based on RMZ
Stream restored from a pipe	Streams located in pipes	25	25/50 daylit	+25

Np = Non-fish perennial stream

Ns = Non-fish seasonal stream

RMZ = Riparian Management Zone, measured from stream polyline (center) vs. ordinary high water mark (OHWM)

 

Summary of Stream Buffer Options: The Buffer Comparison table below summarizes the proposed buffer width options (low, medium, high) compared to existing buffer widths. 

 

Buffer Comparison Table (by Water Types)

Water Type	Stream Type	Existing Buffer Width (feet)	Proposed Buffer	Difference (feet)
Type S (Shoreline)	Lower portion of Swamp Creek, Sammamish River, Lake Washington	See KMC 16.65.020	See KMC 16.65.020 (no change)	See 16.65.020 (no change)
Type F (Fish bearing-salmonid)	Other water bodies used by or containing habitat suitable for salmonid fish	150 – Little Swamp Ck. 100 – all others	Low – 150 Medium – 200 High – 100 min to 231 max (RMZ)	L = +50 M = +100 H = Varies based on RMZ
Type F (Fish bearing-non-salmonid)	Other water bodies used by or containing habitat not suitable for salmonid fish	50	Low – 150 Medium – 200 High – 100 min to 231 max (RMZ)	L = +50 M = +150 H = Varies based on RMZ
Type N (Np and Ns)	Perennial or seasonal non-fish bearing streams	25	Low – 100 Medium – 100 High – 100 min to 231 max (RMZ)	L = +75 M = +75 H = Varies based on RMZ
Stream restored from a pipe	Streams located in pipes	25	25/50 daylit	+25

Np = Non-fish perennial stream

Ns = Non-fish seasonal stream

RMZ = Riparian Management Zone, measured from stream polyline (center) vs. ordinary high water mark (OHWM)

 

Summary of Policy Issues:  There are competing and overlapping goals related to the natural and built environment.  For the natural environment, which includes streams and associated buffers, the goal is to ensure protection, enhancement, and restoration. For the built environment, the goal is to ensure sufficient land is available to accommodate growth for housing and jobs and associated infrastructure (e.g. roads, parks, utilities).  The policy issue for the City Council discussion is how best to balance both goals.  The options for stream buffers have pros and cons and differing implications for ecological function, land use, regulatory framework and compliance with WDFW guidance.  These are summarized on the table below.  Additional information is provided in Attachment #1.

 

Summary of Policy Issues (by Buffer Options)

Stream Buffer Width Option	Ecological Benefit For Streams	Land Use Impact (Total Parcels)	Local Regulatory Framework	WDFW Standards
Low	High benefit for all streams	1208	Provides base stream standards and retains stream classification.	Meets standards for urbanized areas.   Closely aligned with RMZ average approach
Medium	Higher benefit for all streams	1420	-Provides base stream standards and retains stream classification. -Burden on applicants to demonstrate stream enhancement for buffer width reduction.	More aligned with RMZ average approach
High	Highest benefit for all streams	1744	-New classification approach. -Extensive mapping and review	Fully aligned with RMZ approach

Key Policy Questions for City Council Consideration: The following questions are intended to guide discussion and decision-making on preferred policy direction and next steps.

GMA & Growth Targets

• How would each stream buffer option affect Kenmore’s ability to meet GMA-mandated housing and job targets through 2044?
• Would expanding stream buffers significantly reduce the City’s developable land capacity identified in the Comprehensive Plan?
• How should the City balance the Growth Management Act’s growth requirements with its environmental stewardship goals?

Environmental Protection/Regulatory Flexibility

• What level of ecological improvement does the City want to achieve relative to the land area encumbered by new buffer widths?
• How many additional parcels and acres would be impacted under each option, and are there mitigation or incentive tools to offset those impacts?
• Should the City establish differentiated standards for developed versus undeveloped parcels to minimize redevelopment constraints?
• Should existing flexibility tools (variances, buffer averaging, reasonable use exceptions) be expanded to accommodate redevelopment within constrained parcels?

Click here for DRAFT Buffer Comparison Maps. 

Click here for Non-Conforming Buildings by Buffer Option Maps.

Council Action: 

7/28/2025 - First introduction to City Council.  In December 2024, the City Council adopted an updated Natural Environment Element of the Comprehensive Plan during the periodic update of the Plan.

11/24/2025  - City staff and team members from Osborn Consulting and Facet provided a short presentation before City Council discussion. City staff is requesting that the City Council review and discuss stream buffer width options in relation to key policy questions. Meeting recording. 

Next Steps:  At the January 12, 2026, City Council meeting, there will be further City Council discussion and direction on proposed stream buffer options. Following City Council direction staff will draft code amendments.  A public hearing is anticipated in February with adoption of the ordinance by March 2026.

Please contact Todd Hall, Principal Planner at thall@kenmorewa.com if you have questions.

WA Department of Ecology - Wetlands

WA Department of Fish and Wildlife – Riparian Ecosystems, Volume 1: Science Synthesis and Management Implications (2020)

WA Department of Fish and Wildlife – Riparian Ecosystems, Volume 2: Management Recommendations

City of Kenmore GIS Portal