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WDFW tells Thurston planners to use riparian management zones and 'no net loss' standards
Summary
WDFW ecosystem services manager Cara Whitaker told the Thurston County Planning Commission that critical area updates should use site-potential tree height and a 100-foot minimum to set riparian management zone widths, apply protections across all stream types, and adopt monitoring to achieve 'no net loss' of riparian functions.
Cara Whitaker, ecosystem services division manager for the Washington Department of Fish and Wildlife, told the Thurston County Planning Commission that local critical-area regulations should rely on the agency’s best available science to protect riparian functions and avoid ‘‘no net loss’’ of ecological value.
Whitaker briefed commissioners on the Growth Management Act requirements for critical areas, WDFW priorities including riparian ecosystems, salmon recovery and habitat connectivity, and on technical guidance for Riparian Management Zones (RMZs). She recommended using the site-potential tree height at 200 years or a minimum 100-foot ‘‘pollution-removal’’ distance — whichever is wider — to set RMZ outer edges and apply RMZ protections to all stream types.
‘‘If a CAO designates and protects RMZs less than this width, there may be a net loss of riparian function,’’ Whitaker said, arguing that non-fishbearing headwater streams nonetheless deliver nutrients, wood and cool water to downstream habitats and therefore merit the same protections.
WDFW walked the commission through a mapping tool and field methods for determining site-potential tree height, explaining that a professional forester can validate values where on-the-ground conditions differ from mapped data. Whitaker also recommended a monitoring and adaptive-management program at the jurisdiction scale to track whether mitigation and restoration achieve the ‘‘no net loss’’ objective.
Commissioners asked technical questions about how successional changes and invasive species affect site-potential estimates and whether non-fishbearing streams should be treated differently. Whitaker said map outputs combine soil and species data and that regional WDFW staff can advise on local conditions; she offered to follow up with the agency’s science division for clarifications.
The presentation emphasized trade-offs and practicalities: while RMZ widths derived from long-term tree height help maintain bank stability and multiple riparian functions, Whitaker acknowledged in follow-up that jurisdictions will need to adapt guidance for prairie or oak-woodland landscapes where tree height and composition differ from forested sites.
The department provided slides and links to WAC citations and the WDFW Priority Habitats and Species program as implementation references; Whitaker noted those resources are intended to be used as technical guidance and technical-advice contacts are available for local planning staff. The commission asked staff to follow up on specific mapping and monitoring questions and signaled interest in integrating the guidance into the county’s CAO update.
