A. Development in floodplains shall avoid significantly or cumulatively increasing flood hazards. Development shall be consistent with this SMP, as well as guidelines of the Natural Resource Conservation Service, the U.S. Army Corps of Engineers, the Federal Emergency Management Agency and King and Snohomish Counties’ flood hazard management plans.
B. The channel migration zone (CMZ) is considered to be that area of a stream channel which may erode as a result of normal and naturally occurring hydrological and related processes.2 Applicants for shoreline development or modification may submit a site-specific channel migration zone special study if they believe these conditions do not exist on the subject property. The CMZ special study must be prepared consistent with WAC 173-26-221(3)(b), and may include, but is not limited to, historic aerial photographs, topographic mapping, flooding records, and field verification.
C. The following uses and activities may be authorized within the CMZ or floodway:
1. New development or redevelopment landward of existing legal structures, such as levees, that prevent active channel movement and flooding.
2. Development of new or expansion or redevelopment of existing bridges, utility lines, public storm water facilities and outfalls, and other public utility and transportation structures where no other feasible alternative exists or the alternative would result in unreasonable and disproportionate costs. The evaluation of cost differences between options within the CMZ or floodway and outside of the CMZ or floodway shall include the cost of design, permitting, construction and long-term maintenance or repair. For the purposes of this section “unreasonable and disproportionate” means that locations outside of the floodway or CMZ would add more than 20 percent to the total project cost.3 Where such structures are allowed, mitigation shall address adversely impacted functions and processes in the affected shoreline.
3. New or redeveloped measures to reduce shoreline erosion; provided, that it is demonstrated that the erosion rate exceeds that which would normally occur in a natural condition, that the measures do not interfere with fluvial hydrological and geomorphological processes normally acting in natural conditions, and that the measures include appropriate mitigation of adverse impacts to ecological functions associated with the river or stream.
4. Actions that protect or restore the ecosystem-wide processes or ecological functions or development with a primary purpose of protecting or restoring ecological functions and ecosystem-wide processes.
5. Modifications or additions to an existing nonagricultural legal use; provided, that channel migration is not further limited and that the modified or expanded development includes appropriate protection of ecological functions.
6. Repair and maintenance of existing legally established use and developments; provided, that channel migration is not further limited, flood hazards to other uses are not increased, and significant adverse ecological impacts are avoided.
7. Existing and ongoing agricultural activities; provided, that no new restrictions to channel movement are proposed.
D. Existing structural flood hazard reduction measures, such as levees, may be repaired and maintained as necessary to protect legal uses on the landward side of such structures. Increases in height of an existing levee, with any associated increase in width, that may be needed to prevent a reduction in the level of protection of existing legal structures and uses shall be considered an element of repair and maintenance provided the expansion is landward of the ordinary high water mark.
E. New development or new uses in shoreline jurisdiction, including the subdivision of land, shall not be permitted within the CMZ or floodway.
F. New public and private structural flood hazard reduction measures:
1. Shall be approved when a scientific and engineering analysis demonstrates the following:
a. That they are necessary to protect existing development;
b. That nonstructural measures are not feasible; and
c. That adverse impacts on ecological functions and priority species and habitats can be successfully mitigated so as to assure no net loss.
2. Shall be consistent with King and Snohomish Counties’ respective comprehensive flood hazard management plans.
3. Shall be placed landward of associated wetlands and designated shoreline buffers, except for actions that increase ecological functions, such as wetland restoration, or when no other alternative location to reduce flood hazard to existing development is feasible as determined by the shoreline administrator.
G. New public structural flood hazard reduction measures, such as levees, shall dedicate and improve public access pathways unless public access improvements would cause unavoidable health or safety hazards to the public, inherent and unavoidable security problems, unacceptable and unmitigable significant adverse ecological impacts, unavoidable conflict with the proposed use, or a cost that is disproportionate and unreasonable to the total long-term cost of the development. For the purposes of this section “unreasonable and disproportionate” means that the cost of the public access improvements would add more than 20 percent to the total project cost.4
H. In those instances where management of vegetation as required by this SMP conflicts with vegetation provisions included in state, federal or other flood hazard agency documents governing city-authorized, legal flood hazard reduction measures, the vegetation requirements of this SMP will not apply. However, the applicant shall submit documentation of these conflicting provisions with any shoreline permit applications, and shall comply with all other provisions of this section and this SMP that are not strictly prohibited by the approving flood hazard agency.
I. The removal of gravel or other riverbed material for flood management purposes shall be consistent with BMC 13.11.060, Dredging and dredge material disposal, and may be allowed only after a biological and geomorphological study shows that extraction has a long-term benefit to flood hazard reduction, does not result in a net loss of ecological functions, and is part of a comprehensive flood management solution.
J. Transportation facilities shall be located outside the floodway excepting necessary crossings or bridges which shall be placed as perpendicular to the water body as is physically feasible. New transportation facilities shall be designed so that no significant loss of floodway capacity or greater than a one-half-foot increase in the 100-year flood level will result consistent with FEMA standards. The applicant shall provide all necessary studies, reports and engineering analysis which shall be subject to review and modification by the city of Bothell. If proposed transportation facilities effectively provide flood control, they shall comply with policies and regulations of this section. (Ord. 2280 § 7, 2019; Ord. 2112 § 3 (Exh. C), 2013).