Chapter 15.08
FLOODPLAIN MANAGEMENT
Sections:
15.08.010 Statutory authorization.
15.08.030 Methods of reducing flood losses.
15.08.040 Sources and definitions of terms.
15.08.070 Provisions for flood hazard reduction.
15.08.010 Statutory authorization.
The state of Washington has authorized, in Chapter 86.12 RCW, county governments to adopt comprehensive flood control management plans for any drainage basin that is located wholly or partially within the county. Chapter 86.16 RCW requires counties to adopt floodplain management ordinances. Furthermore, the state of Washington has given, in RCW 86.16.020, local governments the authority to exercise state‑wide floodplain management regulations through the administration of the National Flood Insurance Program by adoption of regulations designed to promote the public health, safety, and general welfare of its citizenry. RCW 86.16.045 authorizes the county to adopt floodplain management ordinances or requirements that exceed the minimum federal requirements of the National Flood Insurance Program without following the procedures provided in RCW 86.16.031(8). (Ord. 2006-1, 2006; Ord. 97-2 § 2, 1997).
15.08.020 Purpose and intent.
It is the purpose and intent of this chapter to promote the public health, safety, and general welfare by ensuring that development activities in or around floodplains, riverine flood areas and lacustrine flood areas do not negatively affect the lands’ ability to reduce flood and storm drainage and to minimize and eliminate public and private losses due to flood conditions in specific areas by provisions designed:
A. To protect human life and health;
B. To minimize expenditure of public money and costly flood control projects;
C. To minimize the need for rescue and relief efforts associated with flooding and generally undertaken at the expense of the general public;
D. To minimize prolonged business interruptions;
E. To minimize damage to public facilities and utilities such as water and gas mains, electric, telephone and sewer lines, streets, and bridges located in areas of special flood hazard;
F. To help maintain a stable tax base by providing for the sound use and development of areas of special flood hazard so as to minimize future flood blight areas;
G. To provide a method to notify potential buyers that property is in an area of special flood hazard; and
H. To ensure that those who occupy the areas of special flood hazard assume responsibility for their actions. (Ord. 2006-1, 2006; Ord. 97-2 § 2, 1997).
15.08.030 Methods of reducing flood losses.
To accomplish its purpose and intent, this chapter includes the following methods and provisions for reducing flood losses:
A. Restricting or prohibiting uses which are 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;
B. Requiring that uses vulnerable to floods, including facilities which serve such uses, be protected against flood damage at the time of initial construction;
C. Controlling the alteration of natural floodplains, stream channels, and natural protective barriers, which help accommodate or channel floodwaters;
D. Controlling filling, grading, dredging, and other development in floodways which may increase flood damage; and
E. Preventing or regulating the construction of flood barriers in floodways which will unnaturally divert floodwaters or may increase flood hazards in other areas. (Ord. 2006-1, 2006; Ord. 97-2 § 2, 1997).
15.08.040 Sources and definitions of terms.
A. Sources.
1. Federal Emergency Management Agency, Guide to Flood Insurance Rate Maps, FIA‑14, May 1988, or any additions or revisions which supersede such publication.
2. Merriam Webster’s Collegiate Dictionary, 10th Edition, 1984.
3. Okanogan County GMA Critical Areas Regulations, Ordinance No. 94‑2 (adopted February 2, 1994, and codified in Chapter 14.12 OCC) and subsequent amendments thereto.
4. Master Program for Okanogan County Shoreline Management adopted July 7, 1987, and subsequent amendments thereto.
B. Definitions. Unless specifically defined below, words or phrases used in this chapter shall be interpreted so as to give them the meaning they have in common usage and to give this chapter its most reasonable application.
1. “Appeal” means a request for review of the administrator’s interpretation of any provisions of this chapter.
2. “Area of shallow flooding” means a designated AO or AH zone on the Flood Insurance Rate Map (FIRM). The base flood depths range from one to three feet; a clearly defined channel does not exist; the path of flooding is unpredictable and indeterminate; and velocity flow may be evident. AO is characterized as sheet flow and AH indicates ponding.
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. Designation on maps always includes the letter A.
4. “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.” Designation on maps always includes the letters A or V.
5. “Base flood elevation (BFE)” means the height of the base flood in relation to the National Geodetic Vertical Datum of 1929 (or other datum where specified).
6. “Basement” means any area of the building having its floor sub-grade (below ground level) on all sides.
7. “Critical facility” means a facility for which even the slight chance of flooding might be too great. Critical facilities include, but are not limited to, churches, schools, day care centers, prisons and detention facilities, group care facilities, sewage treatment facilities, nursing homes, hospitals, police, fire and emergency response installations, installations which produce, use, or store hazardous materials or hazardous waste.
8. “Day care center” means any licensed or nonlicensed child care facility that provides care during part of the 24-hour day in a facility other than the family abode of the person or persons under whose direct care children are placed.
9. “Detailed study areas” means those areas covered by the current Flood Insurance Study (FIS) for unincorporated areas of Okanogan County that have been studied by detailed methods, including areas so identified in the FIS, any area for which a letter of map amendment (LOMA) or letter of map revision (LOMR) has been issued, and any areas studied in detail at the request of the Federal Emergency Management Agency (FEMA) since publication of the current FIS. Detailed study entails the use of hydrologic and hydraulic study methods to determine flood hazard data.
10. “Detention facility” means any establishment dedicated to the incarceration of those members of a society deemed punishable for unlawful acts committed against property and/or against any individual or group member of the general public.
11. “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, to include those associated areas relevant to flood management.
12. “Effective FIRM” means the latest FIRM issued by FEMA, which is in effect as of the date shown in the title box of the FIRM as “EFFECTIVE DATE,” “REVISED,” or “MAP REVISED.”
13. “Encroachment” means the construction, placement of fill, or similar alteration of topography in the floodplain that reduces the area available to convey floodwaters.
14. “FIRM” means Flood Insurance Rate Map (see “effective FIRM”).
15. “Flood” or “flooding” means a general and temporary condition of partial or complete inundation of normally dry land areas from:
a. The overland flow of inland or tidal waters; and/or
b. The unusual and rapid accumulation of runoff of surface waters from any source.
16. “Flood damage” means harmful inundation, water erosion of soil, stream banks and beds, harmful deposition by water of eroded and shifting soils and debris upon property or in the beds of streams, or other bodies of water, damages by high water to public roads, highways, bridges, utilities and to works built for protection against floods or inundation, the interruption by floods of travel, communication and commerce, and all other high water influences and results which adversely affect the public health and safety of property. (RCW 86.16.120)
17. “Flood Insurance Rate Map” means the insurance and floodplain management map issued by FEMA that identifies, based on detailed or approximate analysis, areas of 100-year flood hazard in a community. Also shown on the FIRM are actuarial insurance rate zones. In areas studied by detailed analysis, the FIRM also shows BFEs and 500-year floodplain boundaries.
18. “Flood Insurance Study” means the engineering study performed by FEMA to identify flood‑prone areas and other flood data within a community.
19. “Floodplain” or “flood-prone area” means any land area subject to inundation by water from any source (see definition of “flooding”).
20. “Floodplain management” means the operation of a program of corrective and preventive measures for reducing flood damage, including, but not limited to, emergency preparedness plans, flood control works, and floodplain management regulations.
21. “Floodplain management regulations” means those zoning ordinances, subdivision regulations, building codes, health regulations, special purpose ordinances (such as a floodplain ordinance) 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.
22. “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 one foot.
23. “Group care facility” means an agency, other than a foster‑family home, which is maintained and operated for the care of a group of children on a 24-hour basis.
24. “Lacustrine flood hazard area” means those areas subject to inundation by flooding from lakes or ponds.
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 non‑elevation design requirements of this chapter.
26. “Manufactured home” means a structure, transportable in one or more sections, which is built on a permanent chassis and is designed for use with or without a permanent foundation when connected to the required utilities. “Manufactured home” does not include a “recreational vehicle.”
27. “Manufactured home park or subdivision” means a parcel (or contiguous parcels) of land having two or more manufactured home sites for sale, rent, lease or transfer of ownership.
28. “Meander belt” means the area within which a stable river channel can be expected to move back and forth in the present climate. Instability resulting from land use changes or channel constraint can cause erosion beyond the meander belt. Riparian wetlands and related features such as oxbows and sloughs occur within the meander belt.
29. “New construction” means structures for which the start of construction commenced on or after the effective date of the ordinance codified in this chapter.
30. “Nondetailed study areas” means those areas covered by the current Flood Insurance Study (FIS) for unincorporated areas of Okanogan County that have been studied by approximate methods. Study by approximate methods entails extrapolation of data computed for detailed study areas.
31. “Recreational vehicle” means a vehicle which is:
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.
32. “Regulatory floodway” means the channel of a stream plus any adjacent floodplain areas that must be kept free of encroachment so that the 100‑year flood discharge can be conveyed without increasing the base flood elevation more than a specified amount.
33. “Riverine flood hazard area” means those areas related to, formed by, or resembling a river (including tributaries), streams, creeks, etc., subject to inundation by flooding.
34. “Start of construction” includes substantial improvement, and means the date the building permit was issued, provided the actual start of construction, repair, reconstruction, placement or other improvement was within 180 days of the permit issuance date. The actual start means either the first placement of permanent construction of a structure on a site, such as the pouring of slabs or footings, the installation of piles, the construction of columns, or any work beyond the stage of excavation. 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 foundation or the erection of temporary forms.
35. “Structure” means a walled and roofed building including a gas or liquid storage tank that is principally above ground.
36. “Substantial improvement” means any repair, reconstruction, or improvement of a structure, the cost of which equals or exceeds 50 percent of the market value of the structure either:
a. Before the improvement or repair is started; or
b. If the structure has been damaged and is being restored, before the damage occurred. For the purposes of this definition, “substantial improvement” is considered to occur when the first alteration of any wall, ceiling, floor, or other structural part of the building commences, whether or not that alteration affects the external dimensions of the structure.
The term does not include:
a. Any alteration of a structure listed on the National Register of Historic Places or a State Inventory of Historic Places;
b. Any project for improvement and/or of a structure to comply with existing state or local health, sanitary, or safety code specifications which are solely necessary to assure safe living.
37. “Variance” means a grant of relief from the requirements of this chapter which permits construction in a manner that would otherwise be prohibited by this chapter.
38. “Water surface elevation” means the height, in relation to NGVD of 1929 (or other datum where specified), of floods of various magnitudes and frequencies in lacustrine (lake) and riverine flood hazard areas. (Ord. 2006-1, 2006; Ord. 97-2 § 2, 1997).
15.08.050 General provisions.
A. Lands to Which This Chapter Applies. This chapter shall apply to all areas of special flood hazard within the jurisdiction of Okanogan County, identified on Flood Insurance Rate Maps as 100‑year floodplains and maps associated with other special flood studies.
B. Basis for Establishing the Areas of Special Flood Hazard. The basis for establishing local floodplain management regulations shall be the areas designated as special flood hazard areas on the most recent maps provided by the Federal Emergency Management Agency for the National Flood Insurance Program. Best available information shall be used if these maps are not available or sufficient. (RCW 86.16.051)
The areas of special flood hazard identified by the Federal Insurance Administration in a scientific and engineering report entitled “The Flood Insurance Study for the Okanogan County Area” (revised May 2, 1994, and its subsequent revisions) with accompanying Flood Insurance Rate Maps is hereby adopted by reference and declared to be a part of this chapter. The Flood Insurance Study is on file at the Okanogan County office of planning and development.
C. Penalties for Noncompliance. 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. Violation 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 gross misdemeanor. Any person who violates this chapter or fails to comply with any of its requirements shall upon conviction thereof be fined not more than $300.00 or imprisoned for not more than 90 days, or both, for each violation, and in addition shall pay all costs and expenses involved in the case. Nothing herein contained shall prevent Okanogan County from taking such other lawful action as is necessary to prevent or remedy any violation.
D. 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.
E. Interpretation. In the interpretation and application of this chapter, all provisions shall be:
1. Considered as minimum requirements;
2. Liberally construed in favor of the governing body; and
3. Deemed neither to limit nor repeal any other powers granted under state statutes.
F. Warning and Disclaimer of Liability. 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 area of special flood hazards or uses permitted within such areas will be free from flooding or flood damages. This chapter shall not create liability on the part of Okanogan County, any officer or employee thereof, or the Federal Insurance Administration, for any flood damages that result from reliance on this chapter or any administrative decision lawfully made hereunder. (Ord. 2006-1, 2006; Ord. 97-2 § 2, 1997).
15.08.060 Administration.
A. Establishment of Development Permit.
1. Development Permit Required. A development permit shall be obtained before construction or development begins within any area of special flood hazard established in OCC 15.08.050(B). The permit shall be for all structures including manufactured homes, as set forth in OCC 15.08.040(B), Definitions, and for all development including fill and other activities, also as set forth in OCC 15.08.040(B).
2. Application for Development Permit.
a. Application for a development permit shall be made on forms furnished by the Okanogan County office of planning and development and may include but not be limited to: two copies of plans drawn to scale showing the nature, location, dimensions, and elevations of the area in question; existing or proposed structures, fill, storage of materials, drainage facilities, and the location of the foregoing.
b. The following specific information is required on plan drawings:
i. Elevation in relation to mean sea level of the lowest floor (including basement) of all structures;
ii. Elevation in relation to mean sea level to which any structure has been floodproofed;
iii. Certification by a registered professional engineer that the floodproofing methods for any nonresidential structure meet the floodproofing criteria in OCC 15.08.070(B)(2);
iv. Description of the extent to which a watercourse will be altered or relocated as a result of proposed development;
v. Certified topographic data; and
vi. Hydrologic and hydraulic analyses (applicable for nondetailed study areas only).
c. Information required by this chapter for a detailed study area shall be provided by a professional licensed surveyor or a professional licensed engineer.
d. Information required by this chapter for a nondetailed study area shall be provided by a professional licensed engineer on a stable base mylar.
B. Designation of the Administrator.
1. The director of the Okanogan County office of planning and development is hereby appointed to administer and implement this chapter by granting or denying development permit applications in accordance with its provisions.
2. The director may at his/her discretion delegate the administrative requirements of this chapter.
C. Duties and Responsibilities of the Administrator. Duties of the administrator shall include, but not be limited to:
1. Permit Review.
a. Review all development permits to determine that the permit requirements of this chapter have been satisfied.
b. Review all development permits to determine that all necessary permits have been obtained from those federal, state, or local governmental agencies from which prior approval is required.
c. Review all development permits to determine if the proposed development is located in the floodway. If located in the floodway, assure that the encroachment provisions of OCC 15.08.070 are met.
2. Use of Other Base Flood Data. When base flood elevation data has not been provided in accordance with OCC 15.08.050(B), Basis for Establishing the Areas of Special Flood Hazard, the administrator may obtain, review, and reasonably utilize any base flood elevation and floodway data available from a federal, state or other source, in order to administer OCC 15.08.070.
3. Information to Be Obtained and Maintained.
a. Where base flood elevation data is provided through the Flood Insurance Study or required as in subsection (C)(2) of this section, obtain and record the actual 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. For all new or substantially improved floodproofed structures:
i. Verify and record the actual elevation (in relation to mean sea level); and
ii. Maintain required floodproofing certifications.
c. Maintain for public inspection all records pertaining to the provisions of this chapter.
4. Alteration of Watercourses.
a. Notify adjacent communities and the Washington State Department of Ecology prior to any alteration or relocation of a watercourse, and submit evidence of such notification to the Federal Insurance Administration.
b. Require that maintenance is provided within the altered or relocated portion of said watercourse so that the flood-carrying capacity is not diminished.
5. Interpretation of FIRM Boundaries. Make interpretations where needed, as to exact location of the boundaries of the areas of special flood hazards (for example, where there appears to be a conflict between a mapped boundary and actual field conditions). The person contesting the location of the boundary shall be given a reasonable opportunity to appeal the interpretation as provided in subsection (D) of this section.
D. Appeal and Variance Procedures and Variance Conditions.
1. Procedures.
a. The Okanogan County board of adjustment/hearings examiner as established by Okanogan County commissioners shall hear and decide appeals and requests for variances from the requirements of this chapter.
b. The Okanogan County board of adjustment/hearings examiner shall hear and decide appeals when it is alleged there is an error in any requirement, decision, or determination made by the administrator in the enforcement or administration of this chapter.
c. Those aggrieved by the decision of the Okanogan County board of adjustment/hearings examiner, or any taxpayer, may appeal such decision to Okanogan County superior court.
d. In passing upon such applications, the Okanogan County board of adjustment/hearings examiner shall consider all technical evaluations, all relevant factors, standards specified in other sections of this chapter, and:
i. The danger that materials may be swept onto other lands to the injury of others;
ii. The danger to life and property due to flooding or erosion damage;
iii. The susceptibility of the proposed facility and its contents to flood damage and the effect of such damage on the individual owner;
iv. The importance of the services provided by the proposed facility to the community;
v. The necessity to the facility of a waterfront location, where applicable;
vi. The availability of alternative locations for the proposed use which are not subject to flooding or erosion damage;
vii. The compatibility of the proposed use with existing and anticipated development;
viii. The relationship of the proposed use to the comprehensive plan and floodplain management program for that area;
ix. The safety of access to the property in times of flood for ordinary and emergency vehicles;
x. The expected heights, velocity, duration, rate of rise, and sediment transport of the floodwaters and the effects of wave action, if applicable, expected at the site; and
xi. The cost of providing governmental services during and after flood conditions, including maintenance and repair of public utilities and facilities such as sewer, gas, electrical, and water systems, and streets and bridges.
e. Upon consideration of the factors of subsection (D)(1)(d) of this section and the purposes of this chapter, the Okanogan County board of adjustment/hearings examiner may attach such conditions to the granting of variances as it deems necessary to further the purposes of this chapter.
f. The administrator shall maintain the records of all appeal actions and report any variances to the Federal Insurance Administration upon request.
2. Conditions for Variances.
a. Generally, the only condition under which a variance from the elevation standard may be issued is for new construction and substantial improvements to be erected on a lot of one acre or less in size contiguous to and surrounded by lots with existing structures constructed below the base flood level, providing items (i) through (xi) in subsection (D)(1)(d) of this section have been fully considered. As the lot size increases the technical justification required for issuing the variance increases.
b. Variances may be issued for the reconstruction, rehabilitation, or restoration of structures listed on the National Register of Historic Places or the State Inventory of Historic Places, without regard to the procedures set forth in this section.
c. Variances shall not be issued within a designated floodway if any increase in flood levels during the base flood discharge would result.
d. Variances shall only be issued upon a determination that the variance is the minimum necessary, considering the flood hazard, to afford relief.
e. Variances shall only be issued upon:
i. A showing of good and sufficient cause;
ii. A determination that failure to grant the variance would result in exceptional hardship to the applicant;
iii. A determination that the granting of a variance will not result in increased flood heights, additional threats to public safety, or extraordinary public expense; create nuisances; cause fraud on or victimization of the public as identified in subsection (D)(1)(d) of this section or conflict with existing local laws or ordinances.
f. Variances as interpreted in the National Flood Insurance Program are based on the general zoning law principle that they pertain to a physical piece of property; they are not personal in nature and do not pertain to the structure, its inhabitants, economic or financial circumstances. They primarily address small lots in densely populated residential neighborhoods. As such, variances from the flood elevations should be quite rare.
g. Variances may be issued for nonresidential buildings in very limited circumstances to allow a lesser degree of floodproofing than watertight or dry floodproofing, where it can be determined that such action will have low damage potential, complies with all other variance criteria except subsection (D)(2)(a) of this section and otherwise complies with OCC 15.08.070(A)(1) and (2) of the general standards.
h. Any applicant to whom a variance is granted shall be given written notice that the structure will be permitted to be built with a lowest floor elevation below the base flood elevation and that the cost of flood insurance will be commensurate with the increased risk resulting from the reduced lowest floor elevation. (Ord. 2006-1, 2006; Ord. 97-2 § 2, 1997).
15.08.070 Provisions for flood hazard reduction.
A. General Standards. In all areas of special flood hazards, the following standards are required:
1. Anchoring.
a. All new construction and substantial improvements shall be anchored to prevent flotation, collapse, or lateral movement of the structure. Substantial improvements shall include any raw sewage line or extension of any such line.
b. All manufactured homes must 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 (reference FEMA’s Manufactured Home Installation in Flood Hazard Areas guidebook for additional techniques). See specific standards in subsection (B)(3) of this section.
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. Utilities.
a. All new and replacement water supply systems shall be designed to eliminate infiltration of floodwaters into the system.
b. New and replacement sanitary sewage systems shall be designed to eliminate infiltration of floodwaters into the systems and discharge from the systems into floodwaters.
c. On‑site waste disposal systems shall be located to avoid impairment to them or contamination from them during flooding.
4. Subdivision, Short Plat, Binding Site Plan, Planned Development Proposals.
a. All subdivision, short plat, binding site plan, planned development proposals shall be consistent with the need to minimize flood damage.
b. All subdivision, short plats, binding site plan, planned development proposals shall have public utilities and facilities such as sewer, gas, electrical, and water systems located and constructed to minimize flood damage.
c. All subdivision, short plat, binding site plan, planned development proposals shall have adequate drainage provided to reduce exposure to flood damage.
d. Where base flood elevation data has not been provided or is not available from another authoritative source, it shall be generated for subdivision, short plat, binding site plan, planned development proposals and other proposed developments which contain at least five lots or five acres (whichever is less).
5. Review of Building Permits.
a. Detailed Study Area. Information required by this chapter for a detailed study area shall be provided by a professional licensed surveyor and/or a professional licensed engineer.
b. Nondetailed Study Area. Information required by this chapter for a nondetailed study area shall be provided by a professional licensed engineer. Computations of water surface elevations/base flood elevations in open channels may be documented utilizing the Quick‑2 computer program (or its FEMA authorized revisions or replacement programs).
i. Where elevation data is not available either through the Flood Insurance Study or from another authoritative source (OCC 15.08.060(C)(2)) applications for building permits shall be reviewed to assure that proposed construction will be reasonably safe from flooding. The test of reasonableness is a local judgment and includes use of historical data, high water marks, recent surveys, photographs of past flooding, etc., where available. Failure to elevate at least two feet above adjacent grade in these zones may result in higher insurance rates.
B. Specific Standards. In all areas of special flood hazards where base flood elevation data has been provided as set forth in OCC 15.08.050(B), Basis for Establishing the Areas of Special Flood Hazard, or OCC 15.08.060(C)(2), Use of Other Base Flood Data, the following provisions are required:
1. Residential Construction.
a. New construction and substantial improvement of any residential structure shall have the lowest floor, including basement, elevated one foot or more above base flood elevation.
b. 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 floodwaters. Designs for meeting this requirement shall be certified by a registered professional engineer and shall meet or exceed the following minimum criteria:
i. A minimum of two openings having a total net area of not less than one square inch for every square foot of enclosed area subject to flooding shall be provided.
ii. The bottom of all openings shall be no higher than one foot above grade.
iii. Openings may be equipped with screens, louvers, or other coverings or devices; provided, that they permit the automatic entry and exit of floodwaters.
2. Nonresidential Construction. New construction and substantial improvement of any commercial, industrial or other nonresidential structure shall either have the lowest floor, including basement, elevated one foot or more above the level of the base flood elevation; or, together with attendant utility facilities, shall:
a. Be floodproofed so that below one foot above the base flood level the structure is watertight with walls substantially impermeable to the passage of water;
b. Have structural components capable of resisting hydrostatic and hydrodynamic loads and effect of buoyancy;
c. Be certified by a registered professional engineer 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 OCC 15.08.060(C)(2);
d. Nonresidential structures that are elevated, not floodproofed, must meet the same standards for space below the lowest floor as described in subsection (B)(1)(b) of this section;
e. Applicants floodproofing nonresidential buildings shall be notified that flood insurance premiums will be based on rates that are one foot below the floodproofed level (e.g., a building constructed to the base flood level will be rated as one foot below that level).
3. Manufactured Homes.
a. All manufactured homes to be placed or substantially improved within Zones A1‑30, AH, and AE on the community’s FIRM on sites:
i. Outside of a manufactured home park or subdivision;
ii. In a new manufactured home park or subdivision;
iii. In an expansion to an existing manufactured home park or subdivision; or
iv. In an existing manufactured home park or subdivision on which a manufactured home has incurred substantial damage as the result of a flood;
shall be elevated on a permanent foundation such that the lowest floor of the manufactured home is elevated one foot above the base flood elevation and be securely anchored to an adequately anchored foundation system to resist flotation, collapse and lateral movement.
b. Manufactured homes to be placed or substantially improved on sites in an existing manufactured home park or subdivision within Zones A1-30, AH, and AE on the community’s FIRM that are not subject to the above manufactured home provisions shall be elevated so that either:
i. The lowest floor of the manufactured home is elevated one foot above the base flood elevation; or
ii. The manufactured home chassis is supported by reinforced piers or other foundation elements of at least equivalent strength that are no less than 36 inches in height above grade and securely anchored to an adequately anchored foundation system to resist flotation, collapse, and lateral movement.
4. Recreational Vehicles. Recreational vehicles placed on sites within Zones A1‑30, AH and AE on the community’s FIRM shall:
a. Be on the site for fewer than 180 calendar days during a calendar year; and
b. Be fully licensed and ready for highway use on its wheels or jacking system; be attached to the site only by quick-disconnect type utilities and security devices; and have no permanently attached additions; or
c. Be elevated on a permanent foundation such that the lowest floor of the recreational vehicle 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.
5. Critical Facilities. Construction of new critical facilities shall be, to the extent possible, located outside the limits of the special flood hazard area (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 to three feet or more above the level of the base elevation (100‑year) at the site. Floodproofing and sealing measures shall be taken to ensure that toxic substances will not be displaced by or released into floodwaters. Two access routes elevated to or above the level of the base floodplain shall be provided to all critical facilities. Such elevated access routes shall not increase the base flood elevation by one foot or more.
C. Floodways. Located within areas of special flood hazard established in OCC 15.08.050(B) are areas designated as floodways. Since the floodway is an extremely hazardous area due to the velocity of floodwaters which carry debris, potential projectiles, and erosion potential, the following provisions apply:
1. Restriction of land uses within designated floodways include the prohibition of construction or reconstruction of residential structures except for:
a. Repairs, reconstruction, or improvements to a structure which do not increase the ground floor area; and
b. Repairs, reconstruction, or improvements to a structure of which the cost does not exceed 50 percent of the market value of the structure either:
i. Before the repair or reconstruction was started; or
ii. If the structure has been damaged, and is being restored, before damage occurred.
NOTE: Work done on a structure to comply with existing health, sanitary, or safety codes, or to structures identified as historic places may be excluded in the 50 percent determination only if agreed upon and approved by the planning director;
2. The minimum requirements for the National Flood Insurance Program;
3. The state requirements adopted pursuant to RCW 86.16.031(8) that are applicable to the county;
4. Encroachments, including fill, new construction, substantial improvements, and other development are prohibited unless certification by a professional engineer is provided demonstrating through hydrologic and hydraulic analysis performed in accordance with standard engineering practice that encroachments shall not result in any increase in flood levels, increase flood velocities or erosion potential on- or off‑site, or diminish the flood alleviation capacity of the river system;
5. If this subsection C is satisfied, all new construction and substantial improvements shall comply with all applicable flood hazard reduction provisions of this section.
NOTE: Where base flood elevations have been provided but floodways have not, subsection D of this section applies.
D. Encroachments. The cumulative effect of any proposed development, when combined with all other existing and anticipated development, shall not increase the water surface elevation of the base flood more than one foot at any point as determined by a registered professional engineer.
E. 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 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 these areas the following provisions apply:
1. New construction and substantial improvements of residential structures within AO zones shall have the lowest floor (including basement) elevated above the highest adjacent grade of the building site, to or above the depth number specified on the FIRM (at least two feet 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, to or 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 floodproofed 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 subsection (B)(2)(c) of this section.
3. Require adequate drainage paths around structures on slopes to guide floodwaters around and away from proposed structures.
4. Recreational vehicles placed on sites within AO zones on the community’s FIRM must either:
a. Be on the site for fewer than 180 consecutive days; and
b. Be fully licensed and ready for highway use on its wheels or a jacking system; be 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 this subsection E and the elevation and anchoring requirements for manufactured homes. (Ord. 2006-1, 2006; Res. 125-2000; Ord. 97-2 § 2, 1997).
15.08.080 Exemptions.
Reserved. (Ord. 2006-1, 2006; Ord. 97-2 § 2, 1997).
15.08.090 Severability.
If any section or provision of this chapter shall be adjudged to be invalid or unconstitutional, such adjudication shall not affect the validity of the chapter as a whole or any section, provision, or part thereof not adjudged to be invalid or unconstitutional. (Ord. 2006-1, 2006; Ord. 97-2 § 2, 1997).