Chapter 16.20 FLOOD DAMAGE PREVENTION

The Legislature of the state of Washington has delegated the responsibility to local governmental units to adopt regulations designed to promote the public health, safety, and general welfare of its citizenry. Therefore, the Columbia County board of commissioners do ordain as follows in this chapter. [Ord. 2023-01 § 3 (Exh. B); Ord. 2020-02 § 2 (Exh. E); Ord. 2006-02 § 1.1.]

16.20.020 Findings of fact.

A. The flood hazard areas of Columbia County are subject to periodic inundation which results in loss of life and property, health and safety hazards, disruption of commerce and governmental services, extraordinary public expenditures for flood protection and relief, and impairment of the tax base, all of which adversely affect the public health, safety, and general welfare.

B. These flood losses are caused by the cumulative effect of obstructions in areas of special flood hazards which increase flood height and velocities and, when inadequately anchored, damage uses in other areas. Uses that are inadequately floodproofed, elevated, or otherwise protected from flood damage also contribute to the flood loss. [Ord. 2023-01 § 3 (Exh. B); Ord. 2020-02 § 2 (Exh. E); Ord. 2006-02 § 1.2.]

16.20.030 Statement of 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:

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 ensure that potential buyers are notified that property is in an area of special flood hazard;

H. To ensure that those who occupy the areas of special flood hazard assume responsibility for their actions; and

I. To participate in and maintain eligibility for flood insurance and disaster relief. [Ord. 2023-01 § 3 (Exh. B); Ord. 2020-02 § 2 (Exh. E); Ord. 2006-02 § 1.3.]

16.20.040 Methods of reducing flood losses.

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

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 flood waters;

D. Controlling filling, grading, dredging, and other development which may increase flood damage; and

E. Preventing or regulating the construction of flood barriers that unnaturally divert flood waters or may increase flood hazards in other areas. [Ord. 2023-01 § 3 (Exh. B); Ord. 2020-02 § 2 (Exh. E); Ord. 2006-02 § 1.4.]

16.20.050 Definitions.

“Accessory structure” is a structure on the same parcel of property as a principal structure and the use of which is incidental to the use of the principal structure. For floodplain management purposes, the term includes only accessory structures used for parking and storage.

“Agricultural structure” is a walled and roofed structure used exclusively for agricultural purposes or uses in connection with the production, harvesting, storage, raising, or drying of agricultural commodities and livestock, including aquatic organisms. Structures that house tools or equipment used in connection with these purposes or uses are also considered to have agricultural purposes or uses.

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

“Appeal” means a request for a review of the interpretation of any provision of this chapter or a request for a variance.

“Area of shallow flooding” is designated as an AO, AH, AR/AO or AR/AH (or VO) zone on the 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; the path of flooding is unpredictable and indeterminate; and velocity flow may be evident. Such flooding is characterized by ponding or sheet flow. Also referred to as the sheet flow area.

“Area of special flood hazard” is 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.”

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

“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”).

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

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

“Breakaway wall” means a wall that is not part of the structural support of the building and is intended through its design and construction to collapse under specific lateral loading forces, without causing damage to the elevated portion of the building or supporting foundation system.

“Coastal high hazard area” means an area of special flood hazard extending from offshore to the inland limit of a primary frontal dune along an open coast and any other area subject to high velocity wave action from storms or seismic sources. The area is designated on the FIRM as zone V1-30, VE or V.

“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 material or hazardous waste.

“Cumulative substantial damage” means flood-related damages sustained by a structure on two separate occasions during a 10-year period for which the cost of repairs, at the time of each such flood event, on the average, equals or exceeds 25 percent of the market value of the structure before the damage occurred.

“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.

“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.

“Elevation certificate” means an administrative tool of the National Flood Insurance Program (NFIP) that can be used to provide elevation information necessary to ensure compliance with community floodplain management ordinances, 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).

“Existing manufactured home park or subdivision” means a manufactured home park or subdivision for which the construction of facilities for servicing the lots on which the manufactured homes are to be affixed (including, at a minimum, the installation of utilities, the construction of streets, and either final site grading or the pouring of concrete pads) is completed before the effective date on the adopted floodplain management regulations.

“Expansion to an existing manufactured home park or subdivision” means the preparation of additional sites by the construction of facilities for servicing the lots on which the manufactured homes are to be affixed (including the installation of utilities, the construction of streets, and either final site grading or the pouring of concrete pads).

“Flood” or “flooding” means:

1. A general and temporary condition of partial or complete inundation of normally dry land areas from:

a. The overflow of inland or tidal waters; and/or

b. The unusual and rapid accumulation of runoff of surface waters from any source; and/or

c. Mudslides (i.e., mudflows) which are proximately caused by flooding as defined in subsection (1)(b) of this definition 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.

2. 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 (1)(a) of this definition.

“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).

“Flood insurance rate map (FIRM)” means the official map of a community, on which the Federal Insurance Administrator has delineated both the areas of special flood hazards 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).

“Flood insurance study (FIS)” means the official report provided by the Federal Insurance Administration that includes flood profiles, the flood boundary-floodway map, and the water surface elevation of the base flood.

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

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

“Floodproofing” 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. Floodproofed structures are those that have the structural integrity and design to be impervious to flood water below the base flood elevation.

“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.”

“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.

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

“Historic structure” means any structure that is:

1. 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;

2. 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;

3. Individually listed on a local inventory of historic places in communities with historic preservation programs which have been approved by the Secretary of the Interior; or

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

a. By an approved state program as determined by the Secretary of the Interior; or

b. Directly by the Secretary of the Interior in states without approved programs.

“Increased cost of compliance” means a flood insurance claim payment up to $30,000 directly to a property owner for the cost to comply with floodplain management regulations after a direct physical loss caused by a flood. Eligibility for an ICC claim can be through a single instance of “substantial damage” or as a result of “cumulative substantial damage.” (More information can be found in FEMA ICC Manual 301.)

“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 found in CCC 16.20.180(A)(4) (i.e., provided there are adequate flood ventilation openings).

“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 attached to the required utilities. The term “manufactured home” does not include a recreational vehicle.

“Manufactured home park or subdivision” means a parcel (or contiguous parcels) of land divided into two or more manufactured home lots for rent or sale.

“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.

“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.

“New manufactured home park or subdivision” means a manufactured home park or subdivision for which the construction of facilities for servicing the lots on which the manufactured homes are to be affixed (including, at a minimum, the installation of utilities, the construction of streets, and either final site grading or the pouring of concrete pads) is completed on or after the effective date of adopted floodplain management regulations.

“Recreational vehicle” means a vehicle:

1. Built on a single chassis;

2. Four hundred square feet or less when measured at the largest horizontal projection;

3. Designed to be self-propelled or permanently towable by a light duty truck; and

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

“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 date. 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, flood, or other structural part of a building, whether or not that alteration affects the external dimensions of the building.

“Structure” means a walled and roofed building, including a gas or liquid storage tank, that is principally above ground, as well as a manufactured home.

“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.

“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:

1. 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

2. Any alteration of a historic structure; provided, that the alteration will not preclude the structure’s continued designation as a historic structure.

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

“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. 2023-01 § 3 (Exh. B); Ord. 2020-02 § 2 (Exh. E); Ord. 2006-02 § 2.]

16.20.060 Lands to which this chapter applies.

This chapter shall apply to all areas of special flood hazards within the jurisdiction of Columbia County. (44 CFR 59.22(a)) [Ord. 2023-01 § 3 (Exh. B); Ord. 2020-02 § 2 (Exh. E); Ord. 2006-02 § 3.1.]

16.20.070 Basis for establishing the areas of special flood hazard.

The areas of special flood hazard identified by the Federal Insurance Administration in a scientific and engineering report entitled “The Flood Insurance Study for Columbia County” dated May 4, 1988, and any revisions thereto, with an accompanying flood insurance rate map (FIRM), and any revisions thereto, are hereby adopted by reference and declared to be a part of this chapter. The flood insurance study and the FIRM are on file at the Columbia County planning department. The best available information for flood hazard area identification as outlined in CCC 16.20.160(B) shall be the basis for regulation until a new FIRM is issued that incorporates data utilized under CCC 16.20.140(B). (44 CFR 60.3(c)(1)(d)(2)) [Ord. 2023-01 § 3 (Exh. B); Ord. 2020-02 § 2 (Exh. E); Ord. 2006-02 § 3.2.]

16.20.080 Compliance.

All development within special flood hazard areas is subject to the terms of this chapter and other applicable regulations. [Ord. 2023-01 § 3 (Exh. B); Ord. 2020-02 § 2 (Exh. E).]

16.20.090 Enforcement.

Any violation of this chapter shall be subject to the provisions of CCC Title 19, Code Enforcement. [Ord. 2023-01 § 3 (Exh. B); Ord. 2020-02 § 2 (Exh. E); Ord. 2006-02 § 3.3. Formerly 16.20.080.]

16.20.100 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 other ordinance, easement, covenant, or deed restrictions conflict or overlap, whichever imposes the more stringent restrictions shall prevail. [Ord. 2023-01 § 3 (Exh. B); Ord. 2020-02 § 2 (Exh. E); Ord. 2006-02 § 3.4. Formerly 16.20.090.]

16.20.110 Interpretation.

In the interpretation and application of this chapter, all provisions shall be:

A. Considered as minimum requirements;

B. Liberally construed in favor of the governing body; and

C. Deemed neither to limit nor repeal any other powers granted under state statutes. [Ord. 2023-01 § 3 (Exh. B); Ord. 2020-02 § 2 (Exh. E); Ord. 2006-02 § 3.5. Formerly 16.20.100.]

16.20.120 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 areas of special flood hazard or uses permitted within such areas will be free from flooding or flood damages. This chapter shall not create liability on the part of Columbia 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. 2023-01 § 3 (Exh. B); Ord. 2020-02 § 2 (Exh. E); Ord. 2006-02 § 3.6. Formerly 16.20.110.]

16.20.130 Severability.

This chapter and the various parts thereof are hereby declared to be severable. Should any section of this chapter be declared by the courts to be unconstitutional or invalid, such decisions shall not affect the validity of the chapter as a whole, or any portion thereof other than the section so declared to be unconstitutional or invalid. [Ord. 2023-01 § 3 (Exh. B); Ord. 2020-02 § 2 (Exh. E).]

16.20.140 Establishment of development permit.

A. Development Permit Required. A development permit shall be obtained before construction or development begins within any area of special flood hazard established in CCC 16.20.070. The permit shall be for all structures including manufactured homes, as set forth in CCC 16.20.050, Definitions, and for all development including fill and other activities, also as set forth in CCC 16.20.050, Definitions. (44 CFR 60.3(b)(1))

B. Application for Development Permit. Application for a development permit shall be made on forms furnished by Columbia County and may include, but is not limited to, plans in duplicate 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. Specifically, the following information is required:

1. Elevation in relation to mean sea level of the lowest floor (including basement) of all structures recorded on a current elevation certificate (FEMA Form 81-31) with Section B completed by the local official;

2. Elevation in relation to mean sea level to which any structure has been floodproofed;

3. Where a structure is to be floodproofed, certification by a registered professional engineer or architect that the floodproofing methods for any nonresidential structure meet floodproofing criteria in CCC 16.20.180(B)(2);

4. Description of the extent to which a watercourse will be altered or relocated as a result of the proposed development;

5. Where a structure is proposed in a V, V1-30, or VE zone, a V-zone design certificate;

6. Where development is proposed in a floodway, an engineering analysis indicating no rise of the base flood elevation; and

7. Any other such information that may be reasonably required by the floodplain administrator in order to review the application. [Ord. 2023-01 § 3 (Exh. B); Ord. 2020-02 § 2 (Exh. E); Ord. 2006-02 § 4.1. Formerly 16.20.120.]

16.20.150 Designation of the floodplain administrator.

The planning director/planning manager is hereby appointed to administer, implement and enforce this chapter by granting or denying development permit applications in accordance with its provisions. The floodplain administrator may delegate authority to implement these provisions. (44 CFR 59.22(b)(1)) [Ord. 2023-01 § 3 (Exh. B); Ord. 2020-02 § 2 (Exh. E); Ord. 2006-02 § 4.2. Formerly 16.20.130.]

16.20.160 Duties and responsibilities of the floodplain administrator.

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

A. Permit Review.

1. Review all development permits to determine that the permit requirements of this chapter have been satisfied;

2. All necessary permits have been obtained from those federal, state, or local governmental agencies from which prior approval is required; (44 CFR 60.3(a)(2))

3. The site is reasonably safe from flooding;

4. The proposed development is not located in the floodway. If located in the floodway, assure that the encroachment provisions of CCC 16.20.200 are met;

5. Notify FEMA when annexations occur in the special flood hazard area.

B. Use of Other Base Flood Data (in A and V Zones). When base flood elevation data has not been provided (in A or V zones) in accordance with CCC 16.20.070, 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 CCC 16.20.180, Provisions for flood hazard reduction – Specific standards, and CCC 16.20.200, Floodways. (44 CFR 60.3(b)(4))

C. Information to Be Obtained and Maintained.

1. Where base flood elevation data is provided through the flood insurance study, FIRM, or as required in subsection (B) of this section, obtain and record 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. (44 CFR 60.3(b)(5)(i))

2. For all new or substantially improved floodproofed nonresidential structures where base flood elevation data is provided through the FIS, FIRM, or as required in subsection (B) of this section:

a. Obtain and record the elevation (in relation to mean sea level) to which the structure was floodproofed. (44 CFR 60.3(b)(5)(ii))

b. Maintain the floodproofing certifications required in CCC 16.20.140(B)(3). (44 CFR 60.3 (b)(5)(iii))

3. Certification required by CCC 16.20.200(A), No Rise Standard. (44 CFR 60.3(d)(3)

4. Records of all variance actions, including justification for their issuance. (44 CFR 60.6(a)(6))

5. Improvement and damage calculations.

6. Maintain for public inspection all records pertaining to the provisions of this chapter. (44 CFR 60.3(b)(5)(iii))

D. Alteration of Watercourses. Whenever a watercourse is to be altered or relocated:

1. Notify adjacent communities and the Department of Ecology prior to any alteration or relocation of a watercourse, and submit evidence of such notification to the Federal Insurance Administrator. (44 CFR 60.3(b)(6))

2. Assure that the flood carrying capacity of the altered or relocated portion of said watercourse is maintained. (44 CFR 60.3(b)(7))

E. Interpretation of FIRM Boundaries. Make interpretations, where needed, as to exact location of the boundaries of the areas of special flood hazard (e.g., 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. Such appeals shall be granted consistent with the standards of Section 60.6 of the Rules and Regulations of the National Flood Insurance Program. (44 CFR 59 through 76)

F. Review of Building Permits. (44 CFR 60.3(a)(3)). Where elevation data is not available either through the FIS, FIRM, or from another authoritative source (subsection (B) of this section), applications for floodplain development 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, 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.)

G. Changes to Special Flood Hazard Area.

1. If a project will alter the BFE or boundaries of the SFHA, then the project proponent shall provide the community with engineering documentation and analysis regarding the proposed change. If the change to the BFE or boundaries of the SFHA 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.

2. 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. 2023-01 § 3 (Exh. B); Ord. 2020-02 § 2 (Exh. E); Ord. 2006-02 § 4.3. Formerly 16.20.140.]

16.20.170 Provisions for flood hazard reduction – General standards.

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

A. Anchoring. (44 CFR 60.3(a)(b))

1. 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. (44 CFR 60.3(a)(3)(i))

2. 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. (44 CFR 60.3(b)(8)). For more detailed information, refer to guidebook FEMA-85, “Manufactured Home Installation in Flood Hazard Areas.”

B. Construction Materials and Methods. (44 CFR 60.3(a)(3)(ii) through (iv))

1. All new construction and substantial improvements shall be constructed using materials and utility equipment resistant to flood damage.

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

3. 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. Locating such equipment below the base flood elevation may cause annual flood insurance premiums to be increased.

C. Storage of Materials and Equipment. Storage of materials 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.

D. Utilities. (44 CFR 60.3(a)(5)(6))

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

2. Water wells shall be located on high ground that is not in the floodway;

3. 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;

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

E. Subdivision Proposals. (44 CFR 60.3(a)(4)(b)(3))

1. All subdivision proposals shall be consistent with the need to minimize flood damage;

2. All subdivision proposals shall have public utilities and facilities, such as sewer, gas, electrical, and water systems located and constructed to minimize or eliminate flood damage;

3. All subdivision proposals shall have adequate drainage provided to reduce exposure to flood damage;

4. Where subdivision proposals and other proposed developments contain greater than 50 lots or five acres (whichever is lesser), base flood elevation data shall be included as part of the application.

F. Review of Building Permits. Where elevation data is not available either through the flood insurance study, FIRM, or from another authoritative source (CCC 16.20.160(B)), 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 that includes use of historical data, high water marks, photographs of past flooding, etc., where available. Failure to elevate at least two feet above the highest adjacent grade in these zones may result in higher insurance rates. (44 CFR 60.3(a)(3)) [Ord. 2023-01 § 3 (Exh. B); Ord. 2020-02 § 2 (Exh. E); Ord. 2006-02 § 5.1. Formerly 16.20.160.]

16.20.180 Provisions for flood hazard reduction – Specific standards.

In all areas of special flood hazard where base flood elevation data has been provided as set forth in CCC 16.20.070, Basis for establishing the areas of special flood hazard, or CCC 16.20.160(B), Use of Other Base Flood Data (in A and V Zones), the provisions set out in subsections (A) through (G) of this section are required. Additional standards were clarified in FEMA Technical Bulletin 11-01 to allow crawlspace construction for buildings located in the special flood hazard areas; however, adopting this provision can result in a 20 percent increase in flood insurance premiums. The following provisions are required (44 CFR 60.3(c)(1)):

A. Residential Construction. (44 CFR 60.3 (c)(5))

1. 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 at least one foot above the BFE.

2. New construction and substantial improvement of any residential structure in an AO zone shall meet the requirements in Appendix A of this chapter.

3. 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.

4. Fully enclosed areas below the lowest floor that are subject to flood 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. 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.

b. The bottom of all openings shall be no higher than one foot above grade.

c. Openings may be equipped with screens, louvers, or other coverings or devices; provided, that they permit the automatic entry and exit of flood waters.

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. Nonresidential Construction. (44 CFR 60.3(C)(3)(4)). New construction and substantial improvement of any commercial, industrial or other nonresidential structure meet the requirements of subsection (B)(1) or (B)(2) of this section:

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

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 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. 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.

b. If located in an AO zone, the structure shall meet the requirements in Appendix A of this chapter.

c. 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 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 for meeting this requirement must either be certified by a registered professional engineer or architect or must meet or exceed the following minimum 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. If the requirements of subsection (B)(1) 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:

a. 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;

b. Have structural components capable of resisting hydrostatic and hydrodynamic loads and effects of buoyancy;

c. 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 CCC 16.20.160(B);

d. Nonresidential structures that are elevated, not floodproofed, must meet the same standards for space below the lowest floor as described in subsection (A)(4) of this section.

Applicants who are floodproofing nonresidential buildings should be notified that flood insurance premiums will be based on rates that are one foot below the floodproofed level (e.g., a building floodproofed to the base flood level will be rated as one foot below). Floodproofing the building an additional foot will reduce insurance premiums significantly.

C. Manufactured Homes. All manufactured homes placed or substantially improved on sites within A1-30, AH, and AE zones 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.

D. Recreational Vehicles. (44 CFR 60.3(C)(14)). Recreational vehicles placed on sites are required to either:

1. Be on the site for fewer than 180 consecutive days; or

2. 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

3. Meet the requirements of subsection (C) of this section and the elevation and anchoring requirements for manufactured homes.

E. Enclosed Area Below the Lowest Floor. If the 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.

F. Detached Accessory Structures.

1. Detached accessory structures used only for parking of vehicles and storage are permitted at grade, without a variance, if:

a. Size is less than or equal to a one-story, two-car garage (600 square feet);

b. The portions of the appurtenant structure located below the BFE must be built using flood-resistant materials;

c. The appurtenant structure must be adequately anchored to prevent flotation, collapse, and lateral movement;

d. Any machinery or equipment servicing the appurtenant structure must be elevated or floodproofed to or above the BFE;

e. The appurtenant structure must comply with floodway encroachment provisions in CCC 16.20.200;

f. The appurtenant structure must be designed to allow for the automatic entry and exit of flood waters in accordance with subsection (A)(4) of this section;

g. The structure shall have low damage potential;

h. If the structure is converted to another use, it must be brought into full compliance with the standards governing such use.

G. Crawlspaces and Basements.

1. The interior grade of a crawlspace below the base flood elevation must not be more than two feet below the lowest adjacent exterior grade.

2. The height of the below-grade crawlspace, measured from the interior grade of the crawlspace to the top of the crawlspace foundation wall, must not exceed four feet at any point.

3. The height limitation is the maximum allowable unsupported wall height according to the engineering analyses and building code requirements for flood hazard areas (refer to FEMA Technical Bulletin 11-01, page 7, Guidance for Pre-Engineered Crawlspaces). This limitation is intended to prevent these crawlspaces from being converted into habitable spaces.

4. There must be an adequate drainage system that removes flood waters from the interior area of the crawlspace. The enclosed area should be drained within a reasonable time after a flood event. The type of drainage system will vary because of the site gradient and other drainage characteristics, such as soil types. Possible options include natural drainage through porous, well-drained soils and drainage systems such as perforated pipes, drainage tiles, or gravel or crushed stone drainage by gravity or mechanical means.

5. The velocity of flood waters at the site should not exceed five feet per second for any crawlspace. For velocities in excess of five feet per second, other foundation types should be used. [Ord. 2023-01 § 3 (Exh. B); Ord. 2020-02 § 2 (Exh. E); Ord. 2016-01 § 7 (Exh. A-3); Ord. 2006-02 § 5.2. Formerly 16.20.170.]

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

In areas with base flood elevations (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. (44 CFR 60.3(c)(10)) [Ord. 2023-01 § 3 (Exh. B); Ord. 2020-02 § 2 (Exh. E); Ord. 2006-02 § 5.3. Formerly 16.20.180.]

16.20.200 Floodways.

Located within areas of special flood hazard established in CCC 16.20.070 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 provisions apply:

A. No Rise Standard. Prohibit encroachments, including fill, new construction, substantial improvements, and other development 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 flood discharge. (44 CFR 60.3(d)(3))

B. Residential Construction in Floodways. Construction or reconstruction of residential structures is prohibited within designated floodways, except for (1) repairs, reconstruction, or improvements to a structure which do not increase the ground floor area; and (2) repairs, reconstruction or improvements to a structure, 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. Any project for improvement of a structure to correct existing violations of state or local health, sanitary, or safety code specifications which have been identified by the local conditions, or to structures identified as historic places, may be excluded in the 50 percent.

1. 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:

a. The new farmhouse is a replacement of an existing farmhouse on the same farm site;

b. There is no potential building site for a replacement farmhouse on the same farm outside the designated floodway;

c. Repairs, reconstruction, or improvements to a farmhouse shall not increase the total square footage of encroachment of the existing farmhouse;

d. A replacement farmhouse shall not exceed the total square footage of encroachment of the farmhouse it is replacing;

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

f. 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;

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

h. 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

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

2. Substantially Damaged Residences in Floodway.

a. For all substantially damaged residential structures, other than farmhouses, located in a designated floodway, 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 structure located in the regulatory floodway, no repair or replacement is allowed per WAC 173-158-070(1).

b. 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:

i. There is no potential safe building location for the replacement residential structure on the same property outside the regulatory floodway;

ii. A replacement residential structure is a residential structure built as a substitute for a legally existing residential structure of equivalent use and size;

iii. Repairs, reconstruction, or replacement of a residential structure shall not increase the total square footage of floodway encroachment;

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

v. New and replacement water supply systems are designed to eliminate or minimize infiltration of flood water into the system;

vi. 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;

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

C. All Other Building Standards Apply in the Floodway. Subsection (A) of this section, No Rise Standard, is satisfied or if construction is allowed pursuant to subsection (B) of this section, Residential Construction in Floodways, all new construction and substantial improvements shall comply with all applicable flood hazard reduction provisions of CCC 16.20.170 through 16.20.220. [Ord. 2023-01 § 3 (Exh. B); Ord. 2020-02 § 2 (Exh. E); Ord. 2006-02 § 5.4. Formerly 16.20.190.]

16.20.210 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 by any Columbia County amendments, shall:

A. Be located and constructed to minimize flood damage;

B. Meet the encroachment limitations of this chapter if located in a regulatory floodway;

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

D. Be constructed of flood-damage-resistant materials;

E. Meet the flood opening requirements of CCC 16.20.180(A)(4); and

F. 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 the building code for wet locations. [Ord. 2023-01 § 3 (Exh. B); Ord. 2020-02 § 2 (Exh. E).]

16.20.220 Critical facility.

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 shall be permissible within the SFHA if no feasible alternative site is available. Critical facilities constructed within the SFHA shall have the lowest flood elevation three feet above BFE or to the height of the 500-year flood, whichever is higher. 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 base flood elevation shall be provided to all critical facilities to the extent possible. [Ord. 2023-01 § 3 (Exh. B); Ord. 2020-02 § 2 (Exh. E); Ord. 2006-02 § 5.7. Formerly 16.20.200.]

16.20.230 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. Note: To be “elevated sufficiently to protect livestock” typically means to be elevated at least one foot above the BFE. [Ord. 2023-01 § 3 (Exh. B); Ord. 2020-02 § 2 (Exh. E).]

16.20.240 Variances.

The variance criteria set forth in this section are based on the general principle of zoning law that variances pertain to a piece of property and are not personal in nature. A variance may be granted for a parcel of property with physical characteristics so unusual that complying with the requirements of this section would create an exceptional hardship to the applicant or the surrounding property owners. The characteristics must be unique to the property and not be shared by adjacent parcels. The unique characteristic must pertain to the land itself, not to the structure, its inhabitants, or the property owners.

It is the duty of Columbia County 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 the flood ordinance are quite rare. The long-term goal of preventing and reducing flood loss and damage can only be met if variances are strictly limited. Therefore, the variance guidelines provided in this section are more detailed and contain multiple provisions that must be met before a variance can be properly granted. The criteria are designed to screen out those situations in which alternatives other than a variance are more appropriate.

Standard variances shall be granted by the hearing examiner, following the process set forth in CCC 18.05.050.

A. Requirements for Variances.

1. Variances shall only be issued:

a. Upon a determination that the granting of a variance will not result in increased flood heights, additional threats to public safety, extraordinary public expense, create nuisances, cause fraud on or victimization of the public, or conflict with existing local laws or ordinances;

b. For the repair, rehabilitation, or restoration of historic structures upon a determination that the proposed repair or rehabilitation will not preclude the structure’s continued designation as a historic structure and the variance is the minimum necessary to preserve the historic character and design of the structure;

c. Upon a determination that the variance is the minimum necessary, considering the flood hazard, to afford relief;

d. Upon a showing of good and sufficient cause;

e. Upon a determination that failure to grant the variance would result in exceptional hardship to the applicant;

f. Upon a showing that the use cannot perform its intended purpose unless it is located or carried out in close proximity to water. This includes only facilities defined in CCC 16.20.050 in the definition of “functionally dependent use.”

2. Variances shall not be issued within any floodway if any increase in flood levels during the base flood discharge would result.

3. Generally, variances may be issued for new construction and substantial improvements to be erected on a lot of one-half acre or less in size contiguous to and surrounded by lots with existing structures constructed below the BFE, provided the procedures of CCC 16.20.140 through 16.20.230 have been fully considered. As the lot size increases beyond one-half acre, the technical justification required for issuing the variance increases.

B. Variance Criteria. In considering variance applications, Columbia County shall consider all technical evaluations, all relevant factors, all standards specified in other sections of this chapter, and:

1. The danger that materials may be swept onto other lands to the injury of others;

2. The danger to life and property due to flooding or erosion damage;

3. The susceptibility of the proposed facility and its contents to flood damage and the effect of such damage on the individual owner;

4. The importance of the services provided by the proposed facility to the community;

5. The necessity to the facility of a waterfront location, where applicable;

6. The availability of alternative locations for the proposed use, which are not subject to flooding or erosion damage;

7. The compatibility of the proposed use with existing and anticipated development;

8. The relationship of the proposed use to the comprehensive plan and floodplain management program for that area;

9. The safety of access to the property in time of flood for ordinary and emergency vehicles;

10. The expected heights, velocity, duration, rate of rise, and sediment transport of the flood waters expected at the site; and

11. The costs of providing governmental services during and after flood conditions, including maintenance and repair of public utilities and facilities, such as sewer, gas, electrical, water system, and streets and bridges.

C. Additional Requirements for the Issuance of a Variance.

1. Any applicant to whom a variance is granted shall be given written notice over the signature of the community official that:

a. The issuance of a variance to construct a structure below the BFE will result in increased premium rates for flood insurance up to amounts as high as $25.00 for $100.00 of insurance coverage; and

b. Such construction below the BFE increases risks to life and property.

2. The floodplain administrator shall maintain a record of all variance actions, including justification for their issuance.

3. The floodplain administrator shall condition the variance as needed to ensure that the requirements and criteria of this chapter are met.

4. Variances as interpreted in the NFIP 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 neighborhoods. As such, variances from flood elevations should be quite rare.

5. A streamlined variance process may be used to approve the wet floodproofing of accessory and agricultural structures, as follows:

a. The floodplain administrator shall review the application and prepare findings of fact to show that the proposal meets all requirements in subsection (D) of this section.

b. The Columbia County planning commission shall review and approve the wet floodproofing variance and findings of fact at a regular planning commission meeting.

D. Accessory Structures and Agricultural Structures. A variance is authorized to be issued for the construction or substantial improvement of accessory structures and agricultural structures provided the requirements of this section and the following are satisfied:

1. Accessory Structures. A determination that the proposed accessory structure:

a. Represents minimal investment and has low damage potential (amount of physical damage, contents damage, and loss of function).

b. Is larger than the size limits specified in CCC 16.20.180(F).

c. Complies with the wet floodproofing construction requirements of subsection (D)(3) of this section.

2. Agricultural Structures. A determination that the proposed agricultural structure:

a. Is used exclusively in connection with the production, harvesting, storage, raising, or drying of agricultural commodities and livestock, or storage of tools or equipment used in connection with these purposes or uses, and will be restricted to such exclusive uses.

b. Has low damage potential (amount of physical damage, contents damage, and loss of function).

c. Does not increase risks and pose a danger to public health, safety, and welfare if flooded and contents are released, including but not limited to the effects of flooding on manure storage, livestock confinement operations, liquefied natural gas terminals, and production and storage of highly volatile, toxic, or water-reactive materials.

d. Complies with the wet floodproofing construction of subsection (D)(3) of this section.

3. Wet Floodproofing Construction Requirements. Wet floodproofed structures shall:

a. Be anchored to resist flotation, collapse, and lateral movement.

b. Have flood-damage-resistant materials below the base flood elevation in compliance with the requirements of CCC 16.20.170(B).

c. Have mechanical, electrical, and utility equipment in compliance with the requirements of CCC 16.20.170(B) and (D).

d. In special flood hazard areas other than coastal high hazard areas, have flood openings in compliance with the requirements of CCC 16.20.180(A)(4). [Ord. 2023-01 § 3 (Exh. B); Ord. 2020-02 § 2 (Exh. E); Ord. 2006-02 § 4.4. Formerly 16.20.150]

Appendix A Standards for shallow flooding areas (AO zones) (44 CFR 60.3(c)7, 8 and 11).

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 additional provisions also apply in AO zones:

A. 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).

B. New construction and substantial improvements of nonresidential structures within AO zones shall either:

1. 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

2. 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 CCC 16.20.180(B)(2)(c).

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

D. Recreational vehicles placed on sites within AO zones on the community’s FIRM shall either:

1. Be on the site for fewer than 180 consecutive days; or

2. 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

3. Meet the requirements of subsections (A) and (C) of this Appendix A and the anchoring requirements for manufactured homes (CCC 16.20.170(A)(1)). [Ord. 2023-01 § 3 (Exh. B); Ord. 2020-02 § 2 (Exh. E).]