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King County has completed a draft Raging River Channel Migration Zone (CMZ) study and map which are now available for public review and comment. Although existing regulations are not being changed, your property may be newly impacted as a result of the new map. A public meeting to discuss the Raging River Channel Migration Zone was held on August 22, 2019, 6:00 – 8:00 p.m. at the Preston Community Center. The public comment period ended on October 6, 2019.

The purpose of the Raging River CMZ study and map is to identify areas along the Raging River from Highway 18 downstream to the Snoqualmie River near Fall City which are at risk from channel migration hazards. Channel migration is a natural process that occurs as a river slowly moves across the floodplain or rapidly shifts into a different location. Using historic information, a CMZ is the area in which the river channel is predicted to move over time. Channel migration is a type of flood hazard, different from inundation (floodwater) hazards (visit the channel migration page for more information).

Following are links to the draft map, the draft study and maps, and the draft amendment to the channel migration public rule (Please visit our Acrobat Help page for help with Acrobat).

Paper copies are available for review at the following two locations:

  1. King County Department of Local Services – Permitting Division, 35030 SE Douglas Street, Suite 210, Snoqualmie
  2. Fall City Library, 33415 SE 42nd Place, Fall City, WA (external link)

Public involvement

King County held a public meeting on August 22, 2019, at the Preston Community Center to present the draft Raging River CMZ study and maps, describe the proposed amendment of the public rule, and answer questions.

The deadline for public comments was October 6, 2019. Comments provided during the public comment period are under review.

Written Public Comments 
Email to: Jeremy Bunn at; or mail to: King County Department of Natural Resources and Parks, Attn: Jeremy Bunn, Project Manager, 201 South Jackson Street, Suite 600, Seattle, WA 98104.

CMZ map preparation and adoption process

The draft CMZ study and map may be revised based on comments received. A final Raging River CMZ study and map will be prepared by the Department of Natural Resources and Parks and provided to the Department of Local services for adoption consistent with King County channel migration public rule, under authority of the King County Code 2.98, 21A.02, and 21A.24. Once adopted, the Raging River CMZ study and map will be used to regulate land use within affected areas​ and to inform implementation of Raging River flood risk reduction projects.

The draft Raging River CMZ study and map were prepared using CMZ mapping methods specified in the King County Channel Migration Zone Public Rule, consistent with policies in the King County Flood Hazard Management Plan, Washington State Shoreline Management Act (external link), and the Washington State Department of Ecology Channel Migration Assessment (external link).


Item Date
Public Meeting August 22, 2019
Public Comment Period Begins August 20, 2019
Public Comment Periods Ends October 6, 2019
Maps become effective late-2019/early 2020

Effects of CMZ mapping on land use

King County prepares CMZ studies and maps to inform the public about channel migration hazards. The Raging River CMZ map will be used to review land-use proposals within the CMZ. An example of channel migration zone land use regulations is that new development generally is not allowed within the channel migration zone mapped as a severe hazard area, and new development may be restricted within the channel migration zone mapped as a moderate hazard area. These are existing land use regulations that are not being revised due to this Raging River CMZ study and map. Visit the channel migration zone page for more information.



For more information about the development of the draft Raging River CMZ study and map or channel migration mapping methods, please contact Jeremy Bunn, Project Manager, River and Floodplain Management Section, Water and Land Resources Division, Department of Natural Resources and Parks.

For more information about King County’s existing land use regulations in channel migration zones, please contact Steve Bottheim, Department of Local Services Permitting Division.