Consultants working with river restoration and geomorphic specialists presented a proposal to update the county’s channel migration zone (CMZ) mapping using more recent data and mapping techniques, and to pursue Department of Ecology funding to underwrite the work.

Why the study was proposed: Chris Johnson and geologist Nick Blake told the board that the county’s existing CMZ maps date from 2005 and can over- or under-predict areas of severe channel migration. Blake said updated mapping would inventory infrastructure that constrains river movement, produce more defensible CMZ delineations, and help the county integrate flood-risk management, habitat restoration and project prioritization.

Commissioner and staff questions: Commissioners asked how revised CMZs would change regulatory setbacks and whether updated maps might impose new restrictions that could drive costs for property owners. Consultants said updated mapping can both shrink and expand regulated areas in different places and that the grant-funded process would include review steps and opportunities for the county to evaluate net benefits and regulatory implications.

County commitment: Presenters requested that the county indicate interest in partnering on the Ecology grant but emphasized that a county “letter of interest” is not an obligation to adopt any new map or to fund implementation. County staff indicated support for pursuing grant options but declined to obligate county matching funds without further details.

Next steps: Consultants will examine the grant’s match requirements and return with a plan; staff said they would bring a recommended path forward for board review once grant rules and potential match sources are known.