Chapter 18.15
FLOODPLAINS
Sections:
18.15.020 Critical area report.
18.15.030 Substantive requirements.
18.15.040 Substantive requirements in floodway.
18.15.060 Warning and disclaimer of liability.
18.15.010 Designation.
Floodplains are those areas with a one (1) percent or greater chance of flooding in any given year. The Director 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 Town as the indicator of where floodplains exist, unless more detailed, current, and convincing evidence indicates a different geographic distribution of areas with a one (1) percent or greater chance of flooding in any given year. Floodplains are shown in Figure 3. [Ord. 2006.07 § 3, 2006; Ord. 2005.13 § 1 (Exh. 1), 2005].
18.15.020 Critical area report.
The Director may waive the critical areas report required in WMC 18.12.090 for developments proposed in the floodplain, but not in the floodway, if the applicable permit application contains sufficient data to verify compliance with the substantive requirements. The critical areas report shall not be waived for watercourse alterations. [Ord. 2006.07 § 3, 2006; Ord. 2005.13 § 1 (Exh. 1), 2005].
18.15.030 Substantive requirements.
In addition to the substantive requirements of WMC 18.12.130, the following requirements shall apply to floodplains.
A. To the extent possible consistent with the development objective, all improvements shall be located on the nonfloodplain portion of the site, if any, or on the highest ground on the site, as far as possible from the flood source.
B. New and substantially improved residential structures shall have the lowest floor, including basement, elevated one (1) foot or more above the one hundred (100) year flood elevation. In addition, new and substantially improved manufactured homes (see Wilkeson critical areas code) shall be securely anchored to resist flotation, collapse, and lateral movement.
C. New and substantially improved nonresidential structures shall either:
1. Have the lowest floor, including basement, elevated one (1) foot or more above the one hundred (100) year flood elevation; or
2. Together with utilities and sanitary facilities, be certified by a registered professional engineer or architect as being flood-proofed, so that below one (1) foot or more above the one hundred (100) year flood level the structure is watertight and capable of resisting hydrostatic and hydrodynamic loads and buoyancy.
D. Fully enclosed areas below the lowest habitable floor that are not flood-proofed shall be certified by a registered professional engineer or architect as designed to resist hydrostatic flood forces.
E. New and replacement water supply systems shall be designed to minimize infiltration of flood waters into the systems.
F. New and replacement sanitary sewage systems and on-site septic systems shall be designed to minimize infiltration of flood waters into and discharges from the system.
G. All new construction and substantial improvements, including electrical, heating, ventilation, plumbing, and air-conditioning equipment, shall be constructed using flood-resistant materials and methods.
H. Alteration of natural watercourses shall be avoided if feasible. If unavoidable, the Director shall notify adjacent communities, the Department of Ecology, and FEMA prior to alteration. Any stream-bank stabilization shall use soft armoring (bioengineering). Removal of vegetation and woody debris shall be minimized. The alteration shall not block side channels or diminish flood-carrying capacity.
I. Development in floodplains shall be designed to minimize impacts to such ecological functions as wildlife movement and aquifer recharge. Fill and grading may be placed in areas which in the event of a one hundred (100) year flood would be covered with relatively static floodwaters but not in a manner which would block side channels or inhibit channel migration.
J. Recreational vehicles shall either be on the site for fewer than one hundred eighty (180) consecutive days or be fully licensed and ready for highway use. [Ord. 2006.07 § 3, 2006; Ord. 2005.13 § 1 (Exh. 1), 2005].
18.15.040 Substantive requirements in floodway.
All developments capable of blocking floodwaters, including new construction, substantial improvements, and fill, but excluding underground improvements and conservation or habitat enhancement projects, are prohibited in the floodway unless a registered professional engineer certifies that the proposed encroachment will not result in any increase in flood levels during a one hundred (100) year flood. [Ord. 2006.07 § 3, 2006; Ord. 2005.13 § 1 (Exh. 1), 2005].
18.15.050 Records.
The Director shall record:
A. The as-built elevation above mean sea level of the lowest habitable floor, including basement, of all new or substantially improved structures, and whether the structure contains a basement;
B. Certificates of flood-proofing and flood elevation; and
C. Permits and variances issued in accordance with this chapter. [Ord. 2006.07 § 3, 2006; Ord. 2005.13 § 1 (Exh. 1), 2005].
18.15.060 Warning and disclaimer of liability.
Because larger floods than the one hundred (100) year flood occur occasionally, and flood heights may be increased by manmade or natural causes, compliance with this chapter does not entirely guarantee against flood damages, and the Town shall not be liable for flood damages that result from reliance on this chapter. [Ord. 2006.07 § 3, 2006; Ord. 2005.13 § 1 (Exh. 1), 2005].
