A. For the purpose of the City’s critical areas regulations, as set forth in Chapter 14.255 SMC, floodplains are those areas that provide important flood storage, conveyance and attenuation functions and include all land within such areas that are subject to a one (1) percent or greater chance of flooding in any given year.
B. Floodplains shall be designated by the Floodplain Administrator in accordance with WAC 365-190-080(3).
1. The Floodplain Administrator shall use the “areas of special flood hazard” as identified on the Federal Emergency Management Administration’s most current Flood Insurance Rate Map for the City as the indicator of where floodplains exist, unless more detailed, current, and convincing evidence indicates otherwise.
2. Floodplains shall include, at a minimum, the 100-year floodplain designations of the Federal Emergency Management Agency and the National Flood Insurance Program.
C. The Floodplain Administrator may waive the critical areas report required by SMC 14.255.060 for developments proposed in the floodplain, if the applicable permit application contains sufficient data to verify compliance with the substantive requirements, except for the following developments:
1. Developments in a designated floodway;
2. Developments that result in watercourse alteration; and
3. Developments located adjacent to other critical areas as defined in Chapter 14.255 SMC.
D. In addition to the requirements of SMC 14.255.040 and this chapter, the following requirements shall apply to floodplains:
1. To the extent possible consistent with the development objective, all improvements shall be located on the non-floodplain portion of the site, if any, or on the highest ground on the site, as far as possible from the flood source.
2. Alteration of natural watercourses, including side channels, tributaries, and channel migration zones, is to be avoided when feasible. If unavoidable, the Floodplain Administrator shall notify adjacent communities, the Department of Ecology, the State Department of Fish and Wildlife, and FEMA prior to alteration. Any stream-bank stabilization shall consider the use of soft armoring or best available armoring science. (Ord. 2400, 2020)