Chapter 21.53
FLOOD DAMAGE PREVENTION

Sections:

21.53.010    Authority.

21.53.020    Purpose.

21.53.030    Methods of reducing flood losses.

21.53.040    Flood warning.

21.53.050    Definitions.

21.53.060    Lands to which this chapter applies.

21.53.070    Basis for establishing the areas of special flood hazard.

21.53.080    Compliance.

21.53.090    Enforcement and penalties.

21.53.100    Abrogation and greater restrictions.

21.53.110    Administration of this chapter.

21.53.120    Duties and responsibilities of the floodplain administrator.

21.53.130    General standards for flood hazard reduction.

21.53.140    Specific standards for flood hazard reduction.

21.53.150    AE and A1-30 zones with base flood elevations but no floodways.

21.53.160    Floodways.

21.53.170    Standards for shallow flooding areas (AO zones).

21.53.180    General requirements for other development.

21.53.190    Critical facilities.

21.53.200    Livestock sanctuaries.

21.53.210    Variances.

21.53.010 Authority.

This chapter is adopted pursuant to Chapter 86.16 RCW and Chapter 173-158 WAC. (Ord. 699 § 6 (Att. A), 2020)

21.53.020 Purpose.

It is the purpose of this chapter to promote the public health, safety, and general welfare; reduce the annual cost of flood insurance; and minimize public and private losses due to flood conditions in specific areas by provisions designed to:

(1) Protect human life and health;

(2) Minimize expenditure of public money for costly flood control projects;

(3) Minimize the need for rescue and relief efforts associated with flooding and generally undertaken at the expense of the general public;

(4) Minimize prolonged business interruptions;

(5) Minimize damage to public facilities and utilities, such as water and gas mains; electric, telephone, and sewer lines; and streets and bridges located in flood hazard areas;

(6) Help maintain a stable tax base by providing for the sound use and development of flood hazard areas so as to minimize blight areas caused by flooding;

(7) Notify potential buyers that the property is in a special flood hazard area;

(8) Notify those who occupy flood hazard areas that they assume responsibility for their actions; and

(9) Participate in and maintain eligibility for flood insurance and disaster relief. (Ord. 699 § 6 (Att. A), 2020)

21.53.030 Methods of reducing flood losses.

In order to accomplish its purposes, this chapter includes methods and provisions for:

(1) Restricting or prohibiting development that is dangerous to health, safety, and property due to water or erosion hazards, or which result in damaging increases in erosion or in flood heights or velocities;

(2) Requiring that development vulnerable to floods be protected against flood damage at the time of initial construction;

(3) Controlling the alteration of natural floodplains, stream channels, and natural protective barriers, which help accommodate or channel flood waters;

(4) Controlling filling, grading, dredging, and other development, which may increase flood damage; and

(5) Preventing or regulating the construction of flood barriers that unnaturally divert flood waters or may increase flood hazards in other areas. (Ord. 699 § 6 (Att. A), 2020)

21.53.040 Flood warning.

The degree of flood protection required by this chapter is considered reasonable for regulatory purposes and is based on scientific and engineering considerations. Larger floods can and will occur on rare occasions. Flood heights may be increased by manmade or natural causes. This chapter does not imply that land outside the areas of special flood hazards or uses permitted within such areas will be free from flooding or flood damages. (Ord. 699 § 6 (Att. A), 2020)

21.53.050 Definitions.

The following words and phrases shall be defined and given the meaning set forth below for the purpose of this chapter. Other words or phrases used in this chapter shall be interpreted so as to give them the meaning they have in common usage and all interpretations shall be made as to give this chapter its most reasonable application.

(1) “Alteration of watercourse” means any action that will change the location of the channel occupied by water within the banks of any portion of a riverine waterbody.

(2) “Area of shallow flooding” means a designated zone AO, AH, AR/AO or AR/AH (or VO) on a community’s Flood Insurance Rate Map (FIRM) with a one percent or greater annual chance of flooding to an average depth of one to three feet where a clearly defined channel does not exist, where the path of flooding is unpredictable, and where velocity flow may be evident. Such flooding is characterized by ponding or sheet flow. Also referred to as the “sheet flow area.”

(3) “Area of special flood hazard” means the land in the floodplain within a community subject to a one percent or greater chance of flooding in any given year. It is shown on the Flood Insurance Rate Map (FIRM) as zone A, AO, AH, A1-30, AE, A99, AR (V, VO, V1-30, VE). “Special flood hazard area” is synonymous in meaning with the phrase “area of special flood hazard.”

(4) “ASCE 24” means the most recently published version of ASCE 24, Flood Resistant Design and Construction, published by the American Society of Civil Engineers.

(5) “Base flood” means the flood having a one percent chance of being equaled or exceeded in any given year (also referred to as the “100-year flood”).

(6) “Base flood elevation (BFE)” means the elevation to which flood water is anticipated to rise during the base flood.

(7) “Basement” means any area of the building having its floor subgrade (below ground level) on all sides.

(8) “Critical facility” means a facility for which even a slight chance of flooding might be too great. “Critical facilities” include, but are not limited to, schools, nursing homes, hospitals, police, fire and emergency response installations, and installations which produce, use, or store hazardous materials or hazardous waste.

(9) “Development” means any manmade change to improved or unimproved real estate, including but not limited to buildings or other structures, mining, dredging, filling, grading, paving, excavation or drilling operations or storage of equipment or materials located within the area of special flood hazard.

(10) “Elevation certificate” means an administrative tool of the National Flood Insurance Program (NFIP) that can be used to provide elevation information, to determine the proper insurance premium rate, and to support a request for a letter of map amendment (LOMA) or letter of map revision based on fill (LOMR-F).

(11) “Elevated building” means, for insurance purposes, a nonbasement building that has its lowest elevated floor raised above ground level by foundation walls, shear walls, posts, piers, pilings, or columns.

(12) “Essential facility” has the same meaning as “essential facility” defined in ASCE 24. Table 1-1 in ASCE 24-14 further identifies building occupancies that are essential facilities.

(13) “Farmhouse” means a single-family dwelling located on a farm site where resulting agricultural products are not produced for the primary consumption or use by the occupants and the farm owner.

(14) “Flood or flooding” means:

(a) A general and temporary condition of partial or complete inundation of normally dry land areas from:

(i) The overflow of inland or tidal waters.

(ii) The unusual and rapid accumulation or runoff of surface waters from any source.

(iii) Mudslides (i.e., mudflows) which are proximately caused by flooding as defined in subsection (14)(a)(ii) of this section and are akin to a river of liquid and flowing mud on the surfaces of normally dry land areas, as when earth is carried by a current of water and deposited along the path of the current.

(b) The collapse or subsidence of land along the shore of a lake or other body of water as a result of erosion or undermining caused by waves or currents of water exceeding anticipated cyclical levels or suddenly caused by an unusually high water level in a natural body of water, accompanied by a severe storm, or by an unanticipated force of nature, such as flash flood or an abnormal tidal surge, or by some similarly unusual and unforeseeable event which results in flooding as defined in subsection (14)(a)(i) of this section.

(15) “Flood elevation study” means an examination, evaluation and determination of flood hazards and, if appropriate, corresponding water surface elevations, or an examination, evaluation and determination of mudslide (i.e., mudflow) and/or flood-related erosion hazards. Also known as a flood insurance study (FIS).

(16) “Flood Insurance Rate Map (FIRM)” means the official map of a community, on which the Federal Insurance Administrator has delineated both the special hazard areas and the risk premium zones applicable to the community. A FIRM that has been made available digitally is called a Digital Flood Insurance Rate Map (DFIRM).

(17) “Floodplain or flood prone area” means any land area susceptible to being inundated by water from any source. See “flood or flooding.”

(18) “Floodplain administrator” means the community official designated by title to administer and enforce the floodplain management regulations.

(19) “Floodplain management regulations” means zoning ordinances, subdivision regulations, building codes, health regulations, special purpose ordinances (such as floodplain ordinances, grading ordinances and erosion control ordinances) and other applications of police power. The term describes such State or local regulations, in any combination thereof, which provide standards for the purpose of flood damage prevention and reduction.

(20) “Flood proofing” means any combination of structural and nonstructural additions, changes, or adjustments to structures which reduce or eliminate risk of flood damage to real estate or improved real property, water and sanitary facilities, structures, and their contents. Flood-proofed structures are those that have the structural integrity and design to be impervious to flood water below the base flood elevation.

(21) “Floodway” means the channel of a river or other watercourse and the adjacent land areas that must be reserved in order to discharge the base flood without cumulatively increasing the water surface elevation more than a designated height. Also referred to as “regulatory floodway.”

(22) “Functionally dependent use” means a use which cannot perform its intended purpose unless it is located or carried out in close proximity to water. The term includes only docking facilities, port facilities that are necessary for the loading and unloading of cargo or passengers, and ship building and ship repair facilities, and does not include long-term storage or related manufacturing facilities.

(23) “Highest adjacent grade” means the highest natural elevation of the ground surface prior to construction next to the proposed walls of a structure.

(24) “Historic structure” means any structure that is:

(a) Listed individually in the National Register of Historic Places (a listing maintained by the Department of the Interior) or preliminarily determined by the Secretary of the Interior as meeting the requirements for individual listing on the National Register;

(b) Certified or preliminarily determined by the Secretary of the Interior as contributing to the historical significance of a registered historic district or a district preliminarily determined by the Secretary to qualify as a registered historic district;

(c) Individually listed on a State inventory of historic places in states with historic preservation programs which have been approved by the Secretary of the Interior; or

(d) Individually listed on a local inventory of historic places in communities with historic preservation programs that have been certified either:

(i) By an approved State program as determined by the Secretary of the Interior; or

(ii) Directly by the Secretary of the Interior in states without approved programs.

(25) “Lowest floor” means the lowest floor of the lowest enclosed area (including basement). An unfinished or flood resistant enclosure, usable solely for parking of vehicles, building access, or storage in an area other than a basement area, is not considered a building’s lowest floor; provided, that such enclosure is not built so as to render the structure in violation of the applicable nonelevation design requirements of this chapter (i.e. provided there are adequate flood ventilation openings).

(26) “Mean sea level” means, for purposes of the National Flood Insurance Program, the vertical datum to which base flood elevations shown on a community’s Flood Insurance Rate Map are referenced.

(27) “New construction” means, for the purposes of determining insurance rates, structures for which the “start of construction” commenced on or after the effective date of an initial Flood Insurance Rate Map or after December 31, 1974, whichever is later, and includes any subsequent improvements to such structures. For floodplain management purposes, “new construction” means structures for which the “start of construction” commenced on or after the effective date of a floodplain management regulation adopted by a community and includes any subsequent improvements to such structures.

(28) One Hundred Year Flood or 100-Year Flood. See “base flood.”

(29) “Recreational vehicle” means a vehicle:

(a) Built on a single chassis;

(b) Four hundred square feet or less when measured at the largest horizontal projection;

(c) Designed to be self-propelled or permanently towable by a light duty truck; and

(d) Designed primarily not for use as a permanent dwelling but as temporary living quarters for recreational, camping, travel, or seasonal use.

(30) “Start of construction” includes substantial improvement and means the date the building permit was issued, provided the actual start of construction, repair, reconstruction, rehabilitation, addition, placement, or other improvement was within 180 days from the date of the permit. The “actual start” means either the first placement of permanent construction of a structure on a site, such as the pouring of slab or footings, the installation of piles, the construction of columns, or any work beyond the stage of excavation; or the placement of a manufactured home on a foundation. Permanent construction does not include land preparation, such as clearing, grading, and filling; nor does it include the installation of streets and/or walkways; nor does it include excavation for a basement, footings, piers, or foundations or the erection of temporary forms; nor does it include the installation on the property of accessory buildings, such as garages or sheds not occupied as dwelling units or not part of the main structure. For a substantial improvement, the actual start of construction means the first alteration of any wall, ceiling, floor, or other structural part of a building, whether or not that alteration affects the external dimensions of the building.

(31) “Structure” means, for floodplain management purposes, a walled and roofed building, including a gas or liquid storage tank, that is principally above ground, as well as a manufactured home.

(32) “Substantial damage” means damage of any origin sustained by a structure whereby the cost of restoring the structure to its before-damaged condition would equal or exceed 50 percent of the market value of the structure before the damage occurred.

(33) “Substantial improvement” means any reconstruction, rehabilitation, addition, or other improvement of a structure, the cost of which equals or exceeds 50 percent of the market value of the structure before the “start of construction” of the improvement. This term includes structures which have incurred “substantial damage” regardless of the actual repair work performed. The term does not, however, include either:

(a) Any project for improvement of a structure to correct previously identified existing violations of State or local health, sanitary, or safety code specifications that have been identified by the local code enforcement official and that are the minimum necessary to assure safe living conditions; or

(b) Any alteration of a “historic structure”; provided, that the alteration will not preclude the structure’s continued designation as a “historic structure.”

(34) “Variance” means a grant of relief by a community from the terms of a floodplain management regulation.

(35) “Water surface elevation” means the height, in relation to the vertical datum utilized in the applicable flood insurance study of floods of various magnitudes and frequencies in the floodplains of coastal or riverine areas.

(36) “Water dependent” means a structure for commerce or industry that cannot exist in any other location and is dependent on the water by reason of the intrinsic nature of its operations. (Ord. 699 § 6 (Att. A), 2020)

21.53.060 Lands to which this chapter applies.

This chapter applies to all special flood hazard areas within the boundaries of the City of Woodinville. (Ord. 699 § 6 (Att. A), 2020)

21.53.070 Basis for establishing the areas of special flood hazard.

The special flood hazard areas identified by the Federal Insurance Administrator in a scientific and engineering report entitled “The Flood Insurance Study (FIS) for King County, Washington and Incorporated Areas” dated August 19, 2020, and any revisions thereto, with accompanying Flood Insurance Rate Maps (FIRMs) dated August 19, 2020, and any revisions thereto, are hereby adopted by reference and declared to be a part of this chapter. The FIS and the FIRM are on file at 17301 133rd Avenue NE, Woodinville, Washington.

The best available information for flood hazard area identification as outlined in WMC 21.53.120(2) shall be the basis for regulation until a new FIRM is issued that incorporates data utilized under WMC 21.53.120(2). (Ord. 699 § 6 (Att. A), 2020)

21.53.080 Compliance.

All development within special flood hazard areas is subject to the terms of this chapter and other applicable regulations. (Ord. 699 § 6 (Att. A), 2020)

21.53.090 Enforcement and penalties.

(1) No structure or land shall hereafter be constructed, located, extended, converted, or altered without full compliance with the terms of this chapter and other applicable regulations. Violations of the provisions of this chapter by failure to comply with any of its requirements (including violations of conditions and safeguards established in connection with conditions), shall constitute a misdemeanor.

(2) Any person who violates this chapter or fails to comply with any of its requirements shall upon conviction thereof be fined not more than $5,000 or imprisoned for not more than one year, or both, for each violation pursuant to Chapter 1.03 WMC, and in addition shall pay all costs and expenses involved in the case. As an alternative, the City may render civil penalties pursuant to the notice of violation provisions set forth in Chapter 1.06 WMC.

(3) Nothing herein contained shall prevent the City from taking such other lawful action as is necessary to prevent or remedy any violation. (Ord. 699 § 6 (Att. A), 2020)

21.53.100 Abrogation and greater restrictions.

This chapter is not intended to repeal, abrogate, or impair any existing easements, covenants, or deed restrictions. However, where this chapter and another ordinance, easement, covenant, or deed restriction conflict or overlap, whichever imposes the more stringent restrictions shall prevail. (Ord. 699 § 6 (Att. A), 2020)

21.53.110 Administration of this chapter.

(1) The development services director or designee is designated as the floodplain administrator and shall administer, implement, and enforce this chapter by granting or denying development permits in accordance with this chapter.

(2) A development improvement permit shall be obtained before construction or development begins within any area of special flood hazard established in WMC 21.53.070. The permit shall be for all structures including manufactured homes and for all development including fill and other activities as defined in WMC 21.53.050. Application submittal requirements for a flood improvement permit are set forth in WMC 21.80.100. (Ord. 699 § 6 (Att. A), 2020)

21.53.120 Duties and responsibilities of the floodplain administrator.

Duties of the floodplain administrator shall include, but not be limited to:

(1) Review all development permits to determine if:

(a) The permit requirements of this chapter have been satisfied;

(b) All other required State and Federal permits have been obtained;

(c) The site is reasonably safe from flooding;

(d) The proposed development is not located in the floodway or if located in the floodway, assure the encroachment provisions in WMC 21.53.160(1) are satisfied.

(e) Notify FEMA when annexations occur in the special flood hazard area.

(2) When base flood elevation data has not been provided (in A or V zones) in accordance with WMC 21.53.070 (Basis for establishing the areas of special flood hazard), the Floodplain Administrator shall obtain, review, and reasonably utilize any base flood elevation and floodway data available from a Federal, State, or other source, in order to administer WMC 21.53.140 (Specific standards for flood hazard reduction), and WMC 21.53.160 (Floodways).

(3) Obtain and maintain the following:

(a) Where base flood elevation data is provided through the FIS, FIRM, or required as in WMC 21.53.120(2), obtain and maintain a record of the actual (as-built) elevation (in relation to mean sea level) of the lowest floor (including basement) of all new or substantially improved structures, and whether or not the structure contains a basement;

(b) Obtain and maintain documentation of the elevation of the bottom of the lowest horizontal structural member in V or VE zones;

(c) For all new or substantially improved floodproofed nonresidential structures where base flood elevation data is provided through the FIS, FIRM, or as required in WMC 21.53.120(2):

(i) Obtain and maintain a record of the elevation (in relation to mean sea level) to which the structure was floodproofed;

(ii) Maintain the floodproofing certifications for flood improvement permits required under WMC 21.53.140(2);

(d) Certification required by WMC 21.53.160(1), which the Building Official shall maintain for public inspection;

(e) Records of all variance actions, including justification for their issuance;

(f) Improvement and damage calculations; and

(g) Maintain for public inspection all records pertaining to the provisions of this chapter.

(4) Whenever a watercourse is to be altered or relocated:

(a) Notify adjacent communities and the Department of Ecology prior to such alteration or relocation of a watercourse and submit evidence of such notification to the Federal Insurance Administrator through appropriate notification means; and

(b) Assure that the flood carrying capacity of the altered or relocated portion of said watercourse is maintained.

(5) Review building permits where elevation data is not available either through the FIS, FIRM, or from another authoritative source (WMC 21.53.120(2)). Applications for floodplain development shall be reviewed to assure that proposed construction will be reasonably safe from flooding. The test of reasonableness includes use of historical data, high water marks, photographs of past flooding, etc., where available. (Failure to elevate habitable buildings at least two feet above the highest adjacent grade in these zones may result in higher insurance rates.)

(6) If a project will alter the base flood elevation or boundaries of the special flood hazard area, then the project proponent shall provide the community with engineering documentation and analysis regarding the proposed change. If the change to the base flood elevation or boundaries of the special flood hazard area would normally require a letter of map change, then the project proponent shall initiate, and receive approval of, a conditional letter of map revision (CLOMR) prior to approval of the development permit. The project shall be constructed in a manner consistent with the approved CLOMR. If a CLOMR application is made, then the project proponent shall also supply the full CLOMR documentation package to the Floodplain Administrator to be attached to the floodplain development permit, including all required property owner notifications. (Ord. 699 § 6 (Att. A), 2020)

21.53.130 General standards for flood hazard reduction.

In all areas of special flood hazards, the following standards are required:

(1) Anchoring.

(a) All new construction and substantial improvements, including those related to manufactured homes, shall be anchored to prevent flotation, collapse, or lateral movement of the structure resulting from hydrodynamic and hydrostatic loads including the effects of buoyancy.

(b) All manufactured homes shall be anchored to prevent flotation, collapse, or lateral movement, and shall be installed using methods and practices that minimize flood damage. Anchoring methods may include, but are not limited to, use of over-the-top or frame ties to ground anchors. For more detailed information, refer to guidebook, FEMA-85, “Manufactured Home Installation in Flood Hazard Areas.”

(2) Construction Materials and Methods.

(a) All new construction and substantial improvements shall be constructed with materials and utility equipment resistant to flood damage.

(b) All new construction and substantial improvements shall be constructed using methods and practices that minimize flood damage.

(c) Electrical, heating, ventilation, plumbing, and air-conditioning equipment and other service facilities shall be designed and/or otherwise elevated or located so as to prevent water from entering or accumulating within the components during conditions of flooding.

(3) Storage of Materials and Equipment.

(a) The storage or processing of materials that could be injurious to human, animal, or plant life if released due to damage from flooding is prohibited in special flood hazard areas.

(b) Storage of other material or equipment may be allowed if not subject to damage by floods and if firmly anchored to prevent flotation, or if readily removable from the area within the time available after flood warning.

(4) Utilities.

(a) All new and replacement water supply systems shall be designed to minimize or eliminate infiltration of flood waters into the systems;

(b) Water wells shall be located on high ground that is not in the floodway (WAC 173-160-171);

(c) New and replacement sanitary sewage systems shall be designed to minimize or eliminate infiltration of flood waters into the systems and discharges from the systems into flood waters;

(d) On-site waste disposal systems shall be located to avoid impairment to them or contamination from them during flooding.

(5) Subdivision Proposals and Development.

(a) All subdivisions, as well as new development, shall:

(i) Be consistent with the need to minimize flood damage;

(ii) Have public utilities and facilities, such as sewer, gas, electrical, and water systems, located and constructed to minimize or eliminate flood damage; and

(iii) Have adequate drainage provided to reduce exposure to flood damage.

(b) Where subdivision proposals and other proposed developments contain greater than 50 lots or five acres (whichever is the lesser) base flood elevation data shall be included as part of the application. (Ord. 699 § 6 (Att. A), 2020)

21.53.140 Specific standards for flood hazard reduction.

In all areas of special flood hazards, the standards for specific uses as prescribed in this section are required:

(1) Residential Construction.

(a) In AE and A1-30 zones or other A-zoned areas where the BFE has been determined or can be reasonably obtained, new construction and substantial improvement of any residential structure shall have the lowest floor, including basement, elevated one foot or more above the BFE. Mechanical equipment and utilities shall be waterproof or elevated least one foot above the BFE.

(b) New construction and substantial improvement of any residential structure in an AO zone shall meet the requirements in WMC 21.53.170.

(c) New construction and substantial improvement of any residential structure in an unnumbered A zone for which a BFE is not available and cannot be reasonably obtained shall be reasonably safe from flooding, but in all cases the lowest floor shall be at least two feet above the highest adjacent grade.

(d) Fully enclosed areas below the lowest floor that are subject to flooding are prohibited or shall be designed to automatically equalize hydrostatic flood forces on exterior walls by allowing for the entry and exit of flood waters. Designs must meet or exceed the following criteria:

(i) Have a minimum of two openings with a total net area of not less than one square inch for every square foot of enclosed area subject to flooding.

(ii) The bottom of all openings shall be no higher than one foot above grade.

(iii) Openings may be equipped with screens, louvers, valves, or other coverings or devices; provided, that they permit the automatic entry and exit of flood water.

(iv) A garage attached to a residential structure, constructed with the garage floor slab below the BFE, must be designed to allow for the automatic entry and exit of flood waters.

Alternatively, a registered engineer or architect may design and certify engineered openings.

(2) Nonresidential Construction. New construction and substantial improvement of any commercial, industrial or other nonresidential structure shall meet the requirements of subsection (2)(a) or (b) of this section.

(a) New construction and substantial improvement of any commercial, industrial or other nonresidential structure shall meet all of the following requirements:

(i) In AE and A1-30 zones or other A-zoned areas where the BFE has been determined or can be reasonably obtained:

(A) New construction and substantial improvement of any commercial, industrial, or other nonresidential structure shall have the lowest floor, including basement, elevated one foot or more above the BFE, or elevated as required by ASCE 24, whichever is greater.

(B) Mechanical equipment and utilities shall be waterproofed or elevated at least one foot above the BFE, or as required by ASCE 24, whichever is greater.

(ii) If located in an AO zone, the structure shall meet the requirements in WMC 21.53.170.

(iii) If located in an unnumbered A zone for which a BFE is not available and cannot be reasonably obtained, the structure shall be reasonably safe from flooding, but in all cases the lowest floor shall be at least two feet above the highest adjacent grade.

(iv) Fully enclosed areas below the lowest floor that are subject to flooding are prohibited or shall be designed to automatically equalize hydrostatic flood forces on exterior walls by allowing for the entry and exit of flood waters. Designs for meeting this requirement must either be certified by a registered professional engineer or architect or must meet or exceed the following minimum criteria:

(A) Have a minimum of two openings with a total net area of not less than one square inch for every square foot of enclosed area subject to flooding.

(B) The bottom of all openings shall be no higher than one foot above grade.

(C) Openings may be equipped with screens, louvers, valves, or other coverings or devices; provided, that they permit the automatic entry and exit of flood water.

(D) A garage attached to a residential structure, constructed with the garage floor slab below the BFE, must be designed to allow for the automatic entry and exit of flood waters.

Alternatively, a registered engineer or architect may design and certify engineered openings.

(b) If the requirements of subsection (2)(a) of this section are not met, then new construction and substantial improvement of any commercial, industrial or other nonresidential structure shall meet all of the following requirements:

(i) Be dry floodproofed so that below one foot or more above the base flood level the structure is watertight with walls substantially impermeable to the passage of water or dry floodproofed to the elevation required by ASCE 24, whichever is greater;

(ii) Have structural components capable of resisting hydrostatic and hydrodynamic loads and effects of buoyancy;

(iii) Be certified by a registered professional engineer or architect that the design and methods of construction are in accordance with accepted standards of practice for meeting provisions of this subsection based on their development and/or review of the structural design, specifications and plans. Such certifications shall be provided to the official as set forth in WMC 21.53.120(3)(b);

(iv) Nonresidential structures that are elevated, not floodproofed, must meet the same standards for space below the lowest floor as described in subsection (1)(d) of this section.

(3) Manufactured Homes. All manufactured homes to be placed or substantially improved on sites shall be elevated on a permanent foundation such that the lowest floor of the manufactured home is elevated one foot or more above the base flood elevation and be securely anchored to an adequately anchored foundation system to resist flotation, collapse and lateral movement.

(4) Recreational Vehicles.

(a) Recreational vehicles placed on sites are required to either:

(i) Be on the site for fewer than 180 consecutive days; or

(ii) Be fully licensed and ready for highway use, on wheels or jacking system, attached to the site only by quick disconnect type utilities and security devices, and have no permanently attached additions; or

(b) Meet the requirements of subsection (3) of this section.

(5) Enclosed Area Below the Lowest Floor. If buildings or manufactured homes are constructed or substantially improved with fully enclosed areas below the lowest floor, the areas shall be used solely for parking of vehicles, building access, or storage.

(6) Appurtenant Structures (Detached Garages and Small Storage Structures). For A Zones (A, AE, A1-30, AH, AO):

(a) Appurtenant structures used solely for parking of vehicles or limited storage may be constructed such that the floor is below the BFE, provided the structure is designed and constructed in accordance with the following requirements:

(i) Use of the appurtenant structure must be limited to parking of vehicles or limited storage;

(ii) The portions of the appurtenant structure located below the BFE must be built using flood resistant materials;

(iii) The appurtenant structure must be adequately anchored to prevent flotation, collapse, and lateral movement;

(iv) Any machinery or equipment servicing the appurtenant structure must be elevated or floodproofed to or above the BFE;

(v) The appurtenant structure must comply with floodway encroachment provisions in WMC 21.53.160(1);

(vi) The appurtenant structure must be designed to allow for the automatic entry and exit of flood waters in accordance with WMC 21.53.140(1)(d);

(vii) The structure shall have low damage potential;

(viii) If the structure is converted to another use, it must be brought into full compliance with the standards governing such use; and

(ix) The structure shall not be used for human habitation.

(b) Detached garages, storage structures, and other appurtenant structures not meeting the above standards must be constructed in accordance with all applicable standards in WMC 21.53.140(1).

(c) Upon completion of the structure, certification that the requirements of this section have been satisfied shall be provided to the Floodplain Administrator for verification. (Ord. 699 § 6 (Att. A), 2020)

21.53.150 AE and A1-30 zones with base flood elevations but no floodways.

In areas with BFEs (but a regulatory floodway has not been designated), no new construction, substantial improvements, or other development (including fill) shall be permitted within zones A1-30 and AE on the community’s FIRM, unless it is demonstrated that the cumulative effect of the proposed development, when combined with all other existing and anticipated development, will not increase the water surface elevation of the base flood more than one foot at any point within the community. (Ord. 699 § 6 (Att. A), 2020)

21.53.160 Floodways.

Located within areas of special flood hazard are areas designated as floodways. Since the floodway is an extremely hazardous area due to the velocity of flood waters that can carry debris, and increase erosion potential, the following apply:

(1) No Rise Standard. Encroachments, including fill, new construction, substantial improvements, and other development are prohibited unless certification by a registered professional engineer is provided demonstrating through hydrologic and hydraulic analyses performed in accordance with standard engineering practice that the proposed encroachment would not result in any increase in flood levels during the occurrence of the base flood discharge.

(2) Residential Construction in Floodways.

(a) Construction or reconstruction of residential structures is prohibited within designated floodways, except for:

(i) Repairs, reconstruction, or improvements to a structure that do not increase the ground floor area; and the cost of which does not exceed 50 percent of the market value of the structure either:

(A) Before the repair or reconstruction is started; or

(B) If the structure has been damaged, and is being restored, before the damage occurred.

(ii) Any project for improvement of a structure to correct existing violations of State or local health, sanitary, or safety code specifications that have been identified by the local code enforcement official and that are the minimum necessary to assure safe living conditions, or to structures identified as historic places, may be excluded in the 50 percent market value of the structure.

(b) Replacement of Farmhouses in Floodway. Repairs, reconstruction, replacement, or improvements to existing farmhouse structures located in designated floodways and that are located on lands designated as agricultural lands of long-term commercial significance under RCW 36.70A.170 may be permitted subject to the following:

(i) The new farmhouse is a replacement for an existing farmhouse on the same farm site;

(ii) There is no potential building site for a replacement farmhouse on the same farm outside the designated floodway;

(iii) Repairs, reconstruction, or improvements to a farmhouse shall not increase the total square footage of encroachment of the existing farmhouse;

(iv) A replacement farmhouse shall not exceed the total square footage of encroachment of the farmhouse it is replacing;

(v) A farmhouse being replaced shall be removed, in its entirety, including foundation, from the floodway within 90 days after occupancy of a new farmhouse;

(vi) For substantial improvements and replacement farmhouses, the elevation of the lowest floor of the improvement and farmhouse respectively, including basement, is a minimum of one foot higher than the BFE;

(vii) New and replacement water supply systems are designed to eliminate or minimize infiltration of flood waters into the system;

(viii) New and replacement sanitary sewerage systems are designed and located to eliminate or minimize infiltration of flood water into the system and discharge from the system into the flood waters; and

(ix) All other utilities and connections to public utilities are designed, constructed, and located to eliminate or minimize flood damage.

(c) Substantially Damaged Residences in Floodway. For all substantially damaged residential structures, other than farmhouses, located in a designated floodway:

(i) The Floodplain Administrator may make a written request that the Department of Ecology assess the risk of harm to life and property posed by the specific conditions of the floodway. Based on analysis of depth, velocity, flood-related erosion, channel migration, debris load potential, and flood warning capability, the Department of Ecology may exercise best professional judgment in recommending to the local permitting authority repair, replacement, or relocation of a substantially damaged structure consistent with WAC 173-158-076. The property owner shall be responsible for submitting to the local government and the Department of Ecology any information necessary to complete the assessment. Without a favorable recommendation from the department for the repair or replacement of a substantially damaged residential structure located in the regulatory floodway, no repair or replacement is allowed per WAC 173-158-070(1).

(ii) A replacement residential structure is a residential structure built as a substitute for a legally existing residential structure of equivalent use and size. Before the repair, replacement, or reconstruction is started, all requirements of the NFIP, the State requirements adopted pursuant to Chapter 86.16 RCW, and all applicable local regulations must be satisfied. In addition, the following conditions must be met:

(A) There is no potential safe building location for the replacement residential structure on the same property outside the regulatory floodway;

(B) Repairs, reconstruction, or replacement of a residential structure shall not increase the total square footage of floodway encroachment;

(C) The elevation of the lowest floor of the substantially damaged or replacement residential structure is a minimum of one foot higher than the BFE;

(D) New and replacement water supply systems are designed to eliminate or minimize infiltration of flood water into the system;

(E) New and replacement sanitary sewerage systems are designed and located to eliminate or minimize infiltration of flood water into the system and discharge from the system into the flood waters; and

(F) All other utilities and connections to public utilities are designed, constructed, and located to eliminate or minimize flood damage.

(3) All Other Building Standards Apply in the Floodway. If subsection (1) of this section is satisfied or construction is allowed pursuant to subsection (2) of this section, all new construction and substantial improvements shall comply with all applicable flood hazard reduction provisions of WMC 21.53.130 through WMC 21.53.200 (provisions for flood hazard reduction). (Ord. 699 § 6 (Att. A), 2020)

21.53.170 Standards for shallow flooding areas (AO zones).

Shallow flooding areas appear on FIRMs as AO zones with depth designations. The base flood depths in these zones range from one to three feet above ground where a clearly defined channel does not exist, or where the path of flooding is unpredictable and where velocity flow may be evident. Such flooding is usually characterized as sheet flow. In addition to other provisions in this chapter, the following shall apply in AO zones:

(1) New construction and substantial improvements of residential structures and manufactured homes within AO zones shall have the lowest floor (including basement and mechanical equipment) elevated above the highest adjacent grade to the structure, one foot or more above the depth number specified in feet on the community’s FIRM (at least two feet above the highest adjacent grade to the structure if no depth number is specified).

(2) New construction and substantial improvements of nonresidential structures within AO zones shall either:

(a) Have the lowest floor (including basement) elevated above the highest adjacent grade of the building site, one foot or more above the depth number specified on the FIRM (at least two feet if no depth number is specified); or

(b) Together with attendant utility and sanitary facilities, be completely flood proofed to or above that level so that any space below that level is watertight with walls substantially impermeable to the passage of water and with structural components having the capability of resisting hydrostatic and hydrodynamic loads and effects of buoyancy. If this method is used, compliance shall be certified by a registered professional engineer or architect as in WMC 21.53.140(1)(d).

(3) Require adequate drainage paths around structures on slopes to guide flood waters around and away from proposed structures.

(4) Recreational vehicles placed on sites within AO zones on the community’s FIRM shall either:

(a) Be on the site for fewer than 180 consecutive days; or

(b) Be fully licensed and ready for highway use, on its wheels or jacking system, attached to the site only by quick disconnect type utilities and security devices, and have no permanently attached additions; or

(c) Meet the requirements of subsections (1) and (3) of this section and the anchoring requirements for manufactured homes in WMC 21.53.130(1). (Ord. 699 § 6 (Att. A), 2020)

21.53.180 General requirements for other development.

All development, including manmade changes to improved or unimproved real estate for which specific provisions are not specified in this chapter or the State building codes with adopted amendments shall:

(1) Be located and constructed to minimize flood damage;

(2) Meet the encroachment limitations of this chapter if located in a regulatory floodway;

(3) Be anchored to prevent flotation, collapse, or lateral movement resulting from hydrostatic loads, including the effects of buoyancy, during conditions of the design flood;

(4) Be constructed of flood damage-resistant materials;

(5) Meet the flood opening requirements of WMC 21.53.140(1)(d); and

(6) Have mechanical, plumbing, and electrical systems above the design flood elevation or meet the requirements of ASCE 24, except that minimum electric service required to address life safety and electric code requirements is permitted below the design flood elevation provided it conforms to the provisions of the electrical part of building code for wet locations. (Ord. 699 § 6 (Att. A), 2020)

21.53.190 Critical facilities.

Construction of new critical facilities shall be, to the extent possible, located outside the limits of the SFHA (100-year floodplain). Construction of new critical facilities shall be permissible within the SFHA if no feasible alternative site is available. Critical facilities constructed within the SFHA shall have the lowest floor elevated three feet above BFE or to the height of the 500-year flood, whichever is higher. Access to and from the critical facility should also be protected to the height utilized above. Floodproofing and sealing measures must be taken to ensure that toxic substances will not be displaced by or released into flood waters. Access routes elevated to or above the level of the BFE shall be provided to all critical facilities to the extent possible. (Ord. 699 § 6 (Att. A), 2020)

21.53.200 Livestock sanctuaries.

Elevated areas for the purpose of creating a flood sanctuary for livestock are allowed on farm units where livestock is allowed. Livestock flood sanctuaries shall be sized appropriately for the expected number of livestock and be elevated sufficiently to protect livestock. Proposals for livestock flood sanctuaries shall meet all procedural and substantive requirements of this chapter. (Ord. 699 § 6 (Att. A), 2020)

21.53.210 Variances.

It is the duty of the City to help protect its citizens from flooding. This need is so compelling and the implications of the cost of insuring a structure built below the base flood elevation are so serious that variances from the flood elevation or from other requirements in this chapter should be rare. The long-term goal of preventing and reducing flood loss and damage can only be met if the granting of variances is strictly limited. The criteria are designed to exclude those situations in which alternatives other than a variance are more appropriate. The provisions for a flood variance are set forth in WMC 21.80.110. (Ord. 699 § 6 (Att. A), 2020)