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Home My WebLink AboutPC 9.3.25_CAO PC BriefingDOCKET #235 CRITICAL AREAS ORDINANCE (CAO) UPDATE Planning Commission Briefing September 3, 2025 Presented by: Mariah Kerrihard, Associate Planner 425-430-7238 mkerrihard@rentonwa.gov Image from Department of Ecology –Vantage Point Photography (2006) Issue: 1.The Growth Management Act (GMA) requires all cities and counties in Washington to adopt regulations protecting “critical areas” to preserve the natural environment, wildlife habitats, and sources of fresh drinking water. Critical areas regulation also encourage public safety by limiting development in areas prone to natural hazards like floods and landslides. 2.Every ten years, counties and cities are required to take legislative action to review and, if needed, revise their comprehensive land use plans and development regulations to ensure the plans and regulations comply with the requirements of the GMA. This update is due by December 31, 2025. 3.The level of review depends on several factors. •If the jurisdiction contains significant, extensive, and/or inadequately protected critical areas, a more detailed review of its policies and development regulations may be necessary. •If new sources of best available science (BAS) are identified (including any management recommendations associated with the new science), the jurisdiction should review those updates for applicability to its critical areas regulations. SUMMARY OF D-235 WHAT IS A CRITICAL AREA? Flood Plain – Department of Ecology https://ecology.wa.gov/water-shorelines/shoreline-coastal- management/hazards/floods-floodplain-planning Frequently flooded areas Wetlands Areas with a critical recharging effect on aquifers used for potable water Geologically hazardous areas Fish and wildlife habitat conservation areas Chinook Salmon – U.S. Fish & Wildlife Service https://www.fws.gov/media/chinook-salmon-mcallister-springs-wa-0 THREE MAIN AREAS OF CHANGE Area Update Rationale Code Updates Up to date terms and references Ensures scientific accuracy Channel Migration Zone (CMZ) Mapping Mapping expands river protections; includes procedures for boundary challenges Safer development for areas near rivers; aligns with state policy Wetland Buffers & Replacement Ratios Some buffer sizes and replacement ratios increased under the Department of Ecology guidance Greater environmental protection and updating to Best Available Science PROPOSED AMENDMENTS TO THE CAO 1.Code Update: •Updating terminology, clarifying document references, and ensuring current standards use best available science 2.Channel Migration Zones (CMZs): •Renton’s Shoreline Master Program contains some references to CMZs and associated land use restrictions. •CMZs are closely linked to floodplain regulations and can extend outside of SMP jurisdiction. •CMZ regulations introduced to the CAO will include opportunities to challenge the CMZ mapped by King County (2015) 3.Wetland Buffers: •Existing wetland buffers and replacement ratios may increase due to best available science. •Staff will provide a jurisdictional comparison to ensure proposed changes protect wetlands while not be creating overly restrictive standards. Cedar River 2025 Springbrook Trail boardwalk crossing Springbrook Creek in Renton, Wash. The public trail is part of the 130-acre Springbrook Creek Wetland and Habitat Mitigation Bank. The critical urban wetland corridor helps control floods, filters drinking water,provides fish and wildlife habitat, and offers residents a chance to relax outdoors. WHAT IS A CHANNEL MIGRATION ZONE? The area that a stream or river could be expected to occupy in the future due to lateral migration or channel avulsion. ➢Often delineated into hazard areas with regulations applied differently ➢Moderate ➢Severe ➢Regulation is for the purpose of prevention of loss of life and damage to property or infrastructure Cedar River – King County derived CMZ LATERAL CHANNEL MIGRATION Occurs when a stream or river moves laterally through bank and floodplain erosion 2015 2024 Skagit River CHANNEL AVULSION Occurs when a stream or river moves or cuts a new mainstem channel across the floodplain. It can happen quickly, or it can develop over time. 1990 2006 Cedar River – Near Ron Regis Park DIFFERENCE BETWEEN MIGRATION AND FLOODING ➢Flooding involves the inundation of the floodplain, areas that are typically dry, with excess water. It is a short-term, temporary condition. ➢Channel migration is the sudden or gradual movement of a channel across it’s floodplain. It can be described as the stream or river modifying or changing course. It is a long-term change. PROPOSED WETLAND BUFFER WIDTHS Category Wetland Characteristic Intensity of Impact of Adjacent Land Use Low Moderate High I and II Bogs and wetlands of high conservation value 125 feet 190 feet 250 feet Forested Based on score for habitat or water quality functions Habitat score of 8 to 9 150 feet 225 feet 300 feet Habitat score of 6 to 7 75 feet 110 feet 150 feet Habitat score of less than 6 and water quality score of 8 to 9 50 feet 75 feet 100 feet Not meeting any of the above characteristics 50 feet 75 feet 100 feet III Habitat score of 8 to 9 150 feet 225 feet 300 feet Habitat score of 6 to 7 75 feet 110 feet 150 feet Habitat score of 3 to 5 40 feet 60 feet 80 feet IV Any habitat score 25 feet 40 feet 50 feet Next Steps: •Briefing on amendments to Planning & Development Committee (09/08) •Planning Commission Public Hearing (09/17) •Planning Commission Deliberations & Recommendations (10/01) Presented by: Mariah Kerrihard, Associate Planner 425-430-7238 mkerrihard@rentonwa.gov Image from Department of Ecology – Vantage Point Photography (2006)