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Committee reviews critical areas code changes; debate over 1-foot vs. 2-foot floodplain freeboard and expanded riparian zones
Summary
Staff and a senior wetland biologist reviewed proposed amendments to the city’s critical areas code (AB24-130) that replace stream buffers with riparian management zones and propose increasing floodplain freeboard from one foot to two feet; council members asked for more local data and a Letter of Map Revision before deciding.
The committee received an overview of proposed amendments to the city’s critical areas code under agenda bill AB24-130, including replacing stream buffers with riparian management zones and a proposed increase in finished-floor freeboard in mapped floodplains.
Planning director introduced the item and said the planning commission has recommended the changes. Jeff Gray, senior wetland biologist with OTAC, briefed the committee on the best-available-science review that informed the draft. Gray said the science-based approach replaces the older “stream corridor” buffer concept with a riparian management zone based on site-potential tree height and the ecological functions those trees support. As a result, staff recommended increasing protective zones on non-fish streams to 100 feet and on Type F (fish-bearing) streams to about 200 feet (the packet and presentation used those round numbers as a compromise average from the site-potential mapping).
On floodplain rules, staff recommended increasing freeboard — the vertical clearance required above the 100-year base flood elevation — from the current 1 foot to 2 feet, citing Department of Ecology guidance and federal trends. Staff emphasized that the proposal would not change FEMA-mapped horizontal floodplain extents; rather, it would raise the required finished-floor elevation for new development inside mapped floodplains. Gray and staff said the change is intended to reflect updated climate-informed flood risk analyses and to conform with emerging federal risk management standards.
Why it matters: the proposed riparian-zone and freeboard changes would affect how new development is sited and designed near streams and inside the floodplain and could change the cost of new projects in downtown and other mapped areas.
Council members raised several concerns and asked for more local analysis before making a decision. The mayor said she preferred not to adopt a 2-foot freeboard without additional justification; Council member Watt and others echoed concerns that raising freeboard to 2 feet may increase construction costs, compress allowable building height given the city’s height rules (which measure height from base flood elevation plus required freeboard) and could affect several projects now in development. Staff clarified that the higher freeboard would apply to new development only and that existing buildings would be grandfathered.
Committee members asked staff to provide comparative data showing what nearby or comparable cities are adopting and to assemble local technical information, including the pending Letter of Map Revision (LOMR/LOMAR) and King County hydrologic information that may show updated base elevations. Staff said they would compile that information and return the remainder of the presentation and supporting data to the next committee meeting; the committee paused the item for additional review rather than sending it immediately to council for a final reading.
Ending: No final vote was taken on AB24-130. Staff will return with additional materials, including comparative municipal standards and any relevant Letter of Map Revision results, before the committee forwards a recommendation to full council.
