King County Council recently approved a new Sea Level Rise Risk Area (SLR Risk Area) and related development regulations for Vashon and Maury Island. The SLR Risk area created an important opportunity to get ahead of expected shifts in coastal flooding as a result of sea level rise. The regulations were adopted in July 2020 as part of the mid-point update of the King County Comprehensive Plan.
The SLR Risk Area extends existing King County “base flood elevation” (BFE) building requirements landward of the coastal high hazard area, also known as the 100-year coastal floodplain. The County had previously required building at least three feet above BFE in the coastal high hazard area. The SLR Risk Area extends this building requirement until the land elevation is equivalent to three feet above BFE of the adjacent flood zone (see figure). This is roughly equivalent to preparing for two to three feet of sea level rise.
The adopted Comp Plan provisions also increase setback requirements on steep slope bluff sites that extend into the coastal high hazard area or the new SLR Risk Area; prohibit the installation of new groundwater wells in the coastal high hazard area; require a surface seal and chloride testing for new groundwater wells installed in the SLR Risk Area; and established a new policy requiring review of sea level rise information every eight years (timed to inform future Comp Plan updates).
For more information on the SLR Risk Area provisions, contact Lara Whitely Binder, King County Climate Preparedness Specialist, at (firstname.lastname@example.org; 206-263-0825).