Critical Areas: Designation, Classification and Mapping of Channel Migration Zones
Department/Issuing Agency: Department of local Services and Department of Natural Resources and Parks
Effective Date: January 11, 2020
Type of Action: Supersedes LUD-17-1-2 PR and amends Chapter 21A-24, King County Code
Approved: /s/ John Taylor
Signed document (PDF, 190 KB)
A. These rules amend LUD-17-1-2-PR and are adopted under K.C.C. chapter 2.98, K.C.C. 21A.02.090 and K.C.C. 21A.24.274. It is the purpose of these rules to:
1. adopt criteria for channel migration designation, classification, and mapping; and
2. adopt channel migration zone studies and maps.
B. King County will prepare CMZ studies and maps for channels located within King County's shoreline jurisdiction.
C. The criteria for channel migration designation, classification, and mapping and the maps adopted by these rules are for use by King County in its review of permit applications under the King County Code. The criteria and maps do not apply to forest practices applications to the Washington Department of Natural Resources.
Applicability and Audience Property owners within the Channel Migration Zone Mapping Areas of the White, Raging and Cedar Rivers in King County. The maps identify the areas and parcels affected by land use, zoning, and permitting restrictions applicable within the Channel Migration Zones.
A. Channel migration hazard area, moderate: the portion of the channel migration zone, as shown on King County’s Channel Migration Zone maps, that lies between the severe channel migration hazard area and the outer boundaries of the channel migration zone.
B. Channel migration hazard area, severe: the portion of the channel migration zone, as shown on King County’s Channel Migration Zone maps, in which there is a higher level of channel migration hazard due to a high likelihood of continued, progressive bank erosion, rapid shifting of channel location or other imminent channel changes.
C. Channel migration zone (CMZ): the area along a river channel within which the channel can be reasonably predicated, based on best available science, to migrate over time as a result of a natural and normally occurring hydrological and related processes when considered with the characteristics of the river and its surroundings.
D. Department: “Department” means the King County Department of Local Services.
21A-24-277 Designation and classification of channel migration zones.
A. Channel migration zones shall be designated based upon a channel migration zone study prepared following the criteria in Appendix A to this rule.
B. Special studies to determine channel migration area boundaries on a specific property may be submitted to the department under section 21A-24-279A of this rule.
21A-24-278A Adopted channel migration zone maps.
The Channel Migration Zone maps and updates, reassessments or adjustments to those maps listed in Appendix B to this Rule are hereby adopted as the Channel Migration Zone maps for King County.
21A-24-279A Updates, reassessments or adjustments to Channel Migration Zone Maps.
A. To the extent practical, a completed CMZ study and map should be updated through its entire study length approximately every 20 years since its date of adoption, or more frequently if unpredicted channel migration render the study and map inaccurate through much of its study area. An updated CMZ study and map shall be prepared using the methods and criteria for channel migration designation, classification and mapping as for a new CMZ study and map, as specified in Appendix A. A completed CMZ study and map remains in effect until it is updated.
B. At the request of a property owner or on its own initiative, the department may reassess and adjust the boundary of a completed CMZ map within a smaller portion of the full CMZ study length and before the entire CMZ map is updated as follows:
1. A property owner may submit a critical area study to the department supporting the property owner’s request for a site-specific reassessment of the CMZ boundary. The critical area study shall be conducted using channel migration mapping methods and criteria specified in Appendix A.
2. The department, in consultation with the department of natural resources and parks, may reassess and adjust the boundary of CMZ or its component hazard areas if it determines that the conditions within a specific portion of an overall CMZ study area have changed to the extent that the existing mapped CMZ boundary is no longer accurate. The reassessment and adjustment shall be made using mapping methods and criteria specified in Appendix A.
3. If the department, in consultation with the department of natural resources and parks, approves an adjustment to an existing CMZ map under subsection B.1 or B.2 of this section, the adjustment will be documented by King County Water and Land Resources Division/River and Floodplain Management Section (WLRD/RFMS) staff in a letter and annotated portion of the adjusted CMZ map. The letter and adjusted map portion shall be kept on file in the records associated with the existing CMZ study and map for that area. KC WLRD/RFMS will record and post all CMZ adjustments to its website www.kingcounty.gov/floodservices. KC WLRD/RFMS shall provide a digital version of the adjusted CMZ boundary(s) to the King County GIS Center for inclusion in the King County digital mapping system. Updates, reassessments or adjustments to CMZ maps approved by the department under this subsection shall be adopted by the provisions of section 21A-24-278A. Public notice to affected and interested parties shall be done in accordance with the provisions of King County Code 2.98.060.A and associated executive policy INF-7-6-EP.IV. Implementation Plan
If a provision of the rules contained herein or its applicability to any person or circumstance is held invalid, the remainder of the provisions of these rules or the application of the provision to other persons or circumstances shall not be affected.
A. This rule will be maintained by the Departments of Local Services and Natural Resources & Parks, or their successor agencies.
VI. Consequences for Noncompliance
King County Department of Local Services, Permitting Division is responsible for enforcing compliance with King County’s land use, zoning and critical areas codes. If non-compliant development occurred within the newly designated Channel Migration Zones, Permitting’s enforcement activities would initiate.
• Appendix A: Preparation of Channel Migration Zone (CMZ) Study and Map
• Appendix B: King County Channel Migration Zone Maps Adopted by this Rule
• Appendix C: Washington State and King County Regulations Regarding Disconnected Migration Areas