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Duval staff brief commission on sensitive areas ordinance update; proposes 100‑foot minimum riparian zone
Summary
Consultant and staff presented draft updates to Duval's Sensitive Areas Ordinance (DMC 14.42), reviewed best available science and Department of Fish and Wildlife recommendations for riparian management zones (RMZs), and proposed using a 100‑foot minimum RMZ rather than variable SPTH‑200 widths.
Duval — City staff and consultants briefed the planning commission Jan. 28 on proposed updates to Duval Municipal Code Chapter 14.42 (sensitive/critical areas). The update incorporates a Best Available Science (BAS) review done by Herrera Environmental Group and responds to Department of Fish and Wildlife (DFW) guidance on riparian protection.
Millian Van Devender of AHBL, the consultant working with the city, said the state requires jurisdictions to use current science when updating critical‑areas regulations and described DFW’s recommendation to adopt Riparian Management Zones sized to Site Potential Tree Height (SPTH 200). Van Devender explained the SPTH 200 approach and demonstrated a DFW GIS tool that maps variable RMZ widths based on soil and dominant tree species. "What they're now saying is that needs to be a riparian management zone, RMZ... the RMZ width needs to be based on site potential tree height, which is abbreviated as SPTH 200," he said.
City staff told commissioners the draft code in their packet takes a more predictable local approach: instead of adopting variable SPTH‑based widths (which in Duval would translate to RMZs ranging widely by site), the proposed ordinance would set a 100‑foot minimum RMZ, allow buffer reduction or averaging only where existing urban conditions have degraded ecological function, and keep performance‑based buffer options in some cases.
Key technical points: Van Devender outlined how SPTH is calculated (an estimated dominant tree height at 200 years) and why DFW considers that metric protective of riparian functions. He also showed examples where SPTH‑based RMZs would be substantially larger than Duval’s current buffer widths (one comparison increased a local stream zone from a 25‑foot buffer to a 235‑foot RMZ under SPTH mapping). Staff emphasized that the SAO updates would apply to future permits only and would not be retroactive to previously approved developments.
Commissioner concerns and process: Commissioners asked about property impacts if stream channels change and how the ordinary high water mark (OHWM) is determined; Van Devender said OHWM reflects stream fluctuations and is the baseline for measuring RMZs. He also noted the city issued a SEPA Determination of Nonsignificance and that the SEPA comment period was open (closing the day after the meeting), and that staff plans to bring the SAO back for a planning commission public hearing in March with a recommendation to council in April.
Next steps: Staff will collect and respond to SEPA comments, refine the draft as warranted, and schedule a public hearing before the planning commission. If the commission recommends adoption, the matter will proceed to city council for final action.
