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King County Flood Control District issues study of South Fork Skykomish River migration zone


View maps and ask questions about a 13-mile channel migration zone along the South Fork Skykomish River at an April 20 meeting with King County floodplain managers, King County Flood Control Supervisor Kathy Lambert and other County representatives.


The King County Flood Control District has issued a draftFlood Control Zone District Logo study of the South Fork Skykomish River’s channel migration zone (CMZ), mapping those areas geologists consider at risk due to natural changes in the river’s location.

The Flood Control District and County officials will host a public meeting to discuss the migration zone from 6-8 p.m. Thursday, April 20, at the Skykomish School Gym at 105 6th St. N. in Skykomish. Flood Control District Supervisor Kathy Lambert plans to attend the meeting.

Channel migration zones are mapped and regulated by King County as critical areas. The natural movement of a river across its floodplain can occur progressively – when erosion on one bank is matched by deposition on the opposite bank – or suddenly, when a channel jumps from one alignment to another.

This newly released study identified areas potentially at risk of channel migration along a 13-mile stretch of the South Fork Skykomish River, starting at the confluence of the Tye and Foss rivers and extending downstream through the town of Skykomish to the King-Snohomish county line.

“The CMZ mapping along the South Fork Skykomish will give residents critical information about natural hazards, and using this information will help the town of Skykomish become a more resilient community,” said Supervisor Lambert.

Josh Baldi, director of the County’s Water and Land Resources Division, said the CMZ mapping is based on detailed LiDAR images and other new information that have enabled geologists to better understand the river’s geomorphology.

“This science-based research helps people and communities near rivers understand the risks and do what is necessary to remain safe,” he said.

The draft CMZ study and accompanying map for the South Fork Skykomish will undergo a 45-day review and public comment period that ends May 15. Once incorporated by amendment into King County’s channel migration public rule, new land development applications within the CMZ will be subject to the County’s existing zoning code regulations.

The April 20 public meeting will give participants a chance to learn more about the channel migration zone along the South Fork Skykomish and hazard-area regulations. The first 30 minutes will be an open house, where participants can view maps and talk to staff, followed by presentations by County representatives from the Department of Permitting and Environmental Review (DPER), which oversees permitting; and the Water and Land Resources Division, which mapped the migration zone. A second open house will run from 7:40 p.m. until the meeting adjourns.

Attendees can submit written or oral comments at the public meeting. Written comments can also be sent to John Bethel at or sent to his attention at King County Department of Natural Resources and Parks, 201 S. Jackson St., Suite 600, Seattle, WA, 98104.

The draft CMZ report and map may be revised based on comments received. A final South Fork Skykomish River CMZ map will be adopted by DPER, consistent with provisions of the public rule.

In addition to regulating new land development within affected areas, the South Fork Skykomish CMZ map and study may inform implementation of South Fork Skykomish River risk reduction projects.

The draft study and maps can also be reviewed at the Skykomish Library and DPER’s office at 35030 S.E. Douglas St., Snoqualmie.

For more information about the draft South Fork Skykomish CMZ study, map or public meeting, contact John Bethel at If you have questions about the King County channel migration public rule or CMZ regulations, contact Steve Bottheim at 206-477-0372 or

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The King County Flood Control District is a special purpose government created to provide funding and policy oversight for flood protection projects and programs in King County. The Flood Control District’s Board is composed of the members of the King County Council. The Water and Land Resources Division of the King County Department of Natural Resources and Parks develops and implements the approved flood protection projects and programs. Information is available at