A.    It is the purpose of this chapter to promote public health, safety, and general welfare, and to minimize public and private losses due to flooding in flood hazard areas by provisions designed to:

1.    Protect human life and health;

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

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

4.    Minimize prolonged business interruptions;

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

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

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

8.    Notify those who occupy special flood hazard areas that they assume responsibility for their actions;

9.    Participate in and maintain eligibility for flood insurance and disaster relief.

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

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

2.    Requiring that development vulnerable to floods, including facilities which serve such uses, be protected against flood damage at the time of initial construction;

3.    Controlling the alteration of natural floodplains, stream channels, and natural protective barriers, which help accommodate or channel floodwaters;

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

5.    Preventing or regulating the construction of flood barriers which will unnaturally divert floodwaters or may increase flood hazards in other areas. (Ord. 1522, 2005; Ord. 1565, 2008; Ord. 1732 § 3 (Exh. B), 2022.)

This chapter shall apply to all flood management areas within the jurisdiction of West Linn. A flood management area permit is required for all development in the flood management area overlay zone. The standards that apply to flood management areas apply in addition to State or federal restrictions governing floodplains or flood hazard areas.

A.    Basis for Establishing the Special Flood Hazard Areas (SFHA). The special flood hazard areas identified by the Federal Insurance Administrator in a scientific and engineering report entitled “Flood Insurance Study: Clackamas County, Oregon and Incorporated Areas,” dated 06/2008 and revised 01/2019, FIRM Panels 41005C0018D, 41005C0019D, 41005C0038D, 41005C0257D, 41005C0259D, 41005C0260D, and 41005C0276D are hereby adopted by reference and declared to be a part of this chapter. The FIS and FIRM panels are on file at West Linn City Hall with the Community Development Department.

B.    Coordination with State of Oregon Specialty Codes. Pursuant to the requirement established in ORS 455 that the City of West Linn administers and enforces the State of Oregon Specialty Codes, the City of West Linn does hereby acknowledge that the Oregon Specialty Codes contain certain provisions that apply to the design and construction of buildings and structures located in special flood hazard areas. Therefore, this chapter is intended to be administered and enforced in conjunction with the Oregon Specialty Codes. (Ord. 1732 § 3 (Exh. B), 2022.)

All development within special flood hazard areas is subject to the terms of this chapter and required to comply with its provisions and all other applicable regulations.

A.    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. Violations of the provisions of this chapter by failure to comply with any of its requirements (including violations of conditions and safeguards established in connection with conditions) shall constitute a civil violation with penalties not to exceed the maximum amount authorized in ORS 455.895. Nothing contained herein shall prevent the City of West Linn from taking such other lawful action as is necessary to prevent or remedy any violation. (Ord. 1732 § 3 (Exh. B), 2022.)

This chapter does not apply to work necessary to protect, repair, or maintain existing public or private structures, utility facilities, roadways, driveways, accessory uses, and exterior improvements, or replace small public structures, utility facilities, or roadways in response to emergencies. Within 30 days after the work has been completed, the party responsible for the work shall initiate a flood management permit designed to analyze any changes effectuated during the emergency and mitigate adverse impacts. (Ord. 1522, 2005; Ord. 1732 § 3 (Exh. B), 2022.)

Prohibited uses in flood management areas include the following:

A.    Any use prohibited in the base zone.

B.    Uncontained areas of hazardous materials as defined by the Oregon Department of Environmental Quality. (Ord. 1732 § 3 (Exh. B), 2022.)

Construction of new critical facilities shall be, to the greatest extent possible, located outside the limits of the SFHA. Construction of new critical facilities shall only be permissible within the SFHA if no feasible alternative site is available. Critical facilities constructed within the SFHA shall have the lowest floor elevated three feet or to the height of the 500-year flood, whichever is higher. Access to and from the critical facility should also be protected to the height utilized above. Floodproofing and sealing measures must be taken to ensure that toxic substances will not be displaced by or released into floodwaters. 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. 1732 § 3 (Exh. B), 2022.)

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

B.    This chapter and the various parts thereof are hereby declared to be severable. If any section, clause, sentence, or phrase of this chapter is held to be invalid or unconstitutional by any court of competent jurisdiction, then said holding shall in no way effect the validity of the remaining portions of this chapter. (Ord. 1732 § 3 (Exh. B), 2022.)

A.    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.

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

C.    This chapter shall not create liability on the part of the City of West Linn, any officer or employee thereof, or the Federal Insurance Administrator for any flood damages that result from reliance on this chapter or any administrative decision lawfully made hereunder. (Ord. 1732 § 3 (Exh. B), 2022.)

A.    The Planning Manager is hereby appointed to administer, implement, and enforce this chapter by granting or denying development permits in accordance with its provisions. The Floodplain Administrator may delegate authority to implement these provisions.

B.    Duties of the floodplain administrator, or their designee, shall include, but not be limited to:

1.    Review all development permits to determine that:

a.    The permit requirements of this chapter have been satisfied;

b.    All other required local, state, and federal permits have been obtained and approved;

c.    Review all development permits to determine if the proposed development is located in a floodway. If located in the floodway assure that the floodway provisions in CDC 27.090 are met;

d.    Review all development permits to determine if the proposed development is located in an area where base flood elevation (BFE) data is available either through the flood insurance study (FIS) or from another authoritative source. If BFE data is not available then ensure compliance with the provisions of CDC 27.070(G);

e.    Provide to building officials the base flood elevation (BFE) and requirement for one foot of freeboard applicable to any building requiring a development permit;

f.    Review all development permit applications to determine if the proposed development qualifies as a substantial improvement as defined in Chapter 2 CDC;

g.    Review all development permits to determine if the proposed development activity is a watercourse alteration. If a watercourse alteration is proposed, ensure compliance with the provisions in CDC 27.070(A); and

h.    Review all development permits to determine if the proposed development activity includes the placement of fill or excavation.

2.    The following information shall be obtained and maintained and shall be made available for public inspection as needed:

a.    Obtain, record, and maintain the actual elevation (in relation to mean sea level) of the lowest floor (including basements) and all attendant utilities of all new or substantially improved structures where base flood elevation (BFE) data is provided through the flood insurance study (FIS), flood insurance rate map (FIRM), or obtained in accordance with CDC 27.070(G).

b.    Obtain and record the elevation (in relation to mean sea level) of the natural grade of the building site for a structure prior to the start of construction and the placement of any fill and ensure that the requirements of CDC 27.090 and subsection (B)(1)(b) of this section are adhered to.

c.    Upon placement of the lowest floor of a structure (including basement) but prior to further vertical construction, obtain documentation, prepared and sealed by a professional licensed surveyor or engineer, certifying the elevation (in relation to mean sea level) of the lowest floor (including basement).

d.    Where base flood elevation data are utilized, obtain as-built certification of the elevation (in relation to mean sea level) of the lowest floor (including basement) prepared and sealed by a professional licensed surveyor or engineer, prior to the final inspection.

e.    Maintain all elevation certificates (EC) submitted to the community.

f.    Obtain, record, and maintain the elevation (in relation to mean sea level) to which the structure and all attendant utilities were floodproofed for all new or substantially improved floodproofed structures where allowed under this chapter and where base flood elevation (BFE) data is provided through the FIS, FIRM, or obtained in accordance with CDC 27.070(G).

g.    Maintain all floodproofing certificates required under this chapter.

h.    Record and maintain all variance actions, including justification for their issuance.

i.    Obtain and maintain all hydrologic and hydraulic analyses performed as required under CDC 27.090.

j.    Record and maintain all substantial improvement and substantial damage calculations and determinations as required under subsection (B)(4) of this section.

k.    Maintain for public inspection all records pertaining to the provisions of this chapter.

3.    Requirement to Notify Other Entities and Submit New Technical Data.

a.    Community Boundary Alterations. The Floodplain Administrator shall notify the Federal Insurance Administrator in writing whenever the boundaries of the community have been modified by annexation or the community has otherwise assumed authority or no longer has authority to adopt and enforce floodplain management regulations for a particular area, to ensure that all flood hazard boundary maps (FHBM) and flood insurance rate maps (FIRM) accurately represent the community’s boundaries. Include within such notification a copy of a map of the community suitable for reproduction clearly delineating the new corporate limits or new area for which the community has assumed or relinquished floodplain management regulatory authority.

b.    Watercourse Alterations. Notify adjacent communities, the Department of Land Conservation and Development, and other appropriate State and federal agencies, prior to any alteration or relocation of a watercourse, and submit evidence of such notification to the Federal Insurance Administration. This notification shall be provided by the applicant to the Federal Insurance Administration as a letter of map revision (LOMR) along with either:

1)    A proposed maintenance plan to assure the flood carrying capacity within the altered or relocated portion of the watercourse is maintained; or

2)    Certification by a registered professional engineer that the project has been designed to retain its flood carrying capacity without periodic maintenance.

The applicant shall be required to submit a conditional letter of map revision (CLOMR) when required under subsection (B)(3)(c) of this section. Ensure compliance with all applicable requirements in subsection (B)(3)(c) of this section and CDC 27.070(A).

c.    Requirement to Submit New Technical Data. A community’s base flood elevations may increase or decrease resulting from physical changes affecting flooding conditions. As soon as practicable, but not later than six months after the date such information becomes available, a community shall notify the Federal Insurance Administrator of the changes by submitting technical or scientific data in accordance with 44 C.F.R. 65.3. The community may require the applicant to submit such data and review fees required for compliance with this section through the applicable FEMA letter of map change (LOMC) process.

The Floodplain Administrator shall require a conditional letter of map revision prior to the issuance of a floodplain development permit for:

1)    Proposed floodway encroachments that increase the base flood elevation; and

2)    Proposed development which increases the base flood elevation by more than one foot in areas where FEMA has provided base flood elevations but no floodway.

An applicant shall notify FEMA within six months of project completion when an applicant has obtained a conditional letter of map revision (CLOMR) from FEMA. This notification to FEMA shall be provided as a letter of map revision (LOMR).

4.    Substantial Improvement and Substantial Damage Assessments and Determinations. Conduct substantial improvement (SI) (as defined in Chapter 2 CDC) reviews for all structural development proposal applications and maintain a record of SI calculations within permit files in accordance with subsection (B)(2) of this section. Conduct substantial damage (SD) (as defined in Chapter 2 CDC) assessments when structures are damaged due to a natural hazard event or other causes. Make SD determinations whenever structures within the special flood hazard area (as established in CDC 27.020(A)) are damaged to the extent that 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.

C.    Establishment of Development Permit.

1.    A development permit shall be obtained before construction or development begins within any area horizontally within the special flood hazard area established in CDC 27.020(A). The development permit shall be required for all structures, including manufactured dwellings, and for all other development, as defined in Chapter 2 CDC, including fill and other development activities.

2.    Application for a development permit may be made on forms furnished by the Floodplain Administrator and may include, but not be 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:

a.    In riverine flood zones, the proposed elevation (in relation to mean sea level), of the lowest floor (including basement) and all attendant utilities of all new and substantially improved structures; in accordance with the requirements of subsection (B)(2) of this section.

b.    Proposed elevation in relation to mean sea level to which any nonresidential structure will be floodproofed.

c.    Certification by a registered professional engineer or architect licensed in the State of Oregon that the floodproofing methods proposed for any nonresidential structure meet the floodproofing criteria for nonresidential structures in CDC 27.080(C)(3).

d.    Description of the extent to which any watercourse will be altered or relocated.

e.    Base flood elevation data for subdivision proposals or other development when required per subsection (B) of this section and CDC 27.070(F).

f.    Substantial improvement calculation for any improvement, addition, reconstruction, renovation, or rehabilitation of an existing structure.

g.    The amount and location of any fill or excavation activities proposed.

D.    Variance Procedure. The issuance of a variance is for floodplain management purposes only. Flood insurance premium rates are determined by federal statute according to actuarial risk and will not be modified by the granting of a variance.

1.    Conditions for Variances.

a.    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 base flood level, in conformance with the provisions of subsections (D)(1)(c), (D)(1)(e) and (D)(2) of this section. As the lot size increases beyond one-half acre, the technical justification required for issuing a variance increases.

b.    Variances shall only be issued upon a determination that the variance is the minimum necessary, considering the flood hazard, to afford relief.

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

d.    Variances shall only be issued upon:

1)    A showing of good and sufficient cause;

2)    A determination that failure to grant the variance would result in exceptional hardship to the applicant;

3)    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 laws or ordinances.

e.    Variances may be issued by a community for new construction and substantial improvements and for other development necessary for the conduct of a functionally dependent use provided that the criteria of subsections (D)(1)(b) through (d) of this section are met, and the structure or other development is protected by methods that minimize flood damages during the base flood and create no additional threats to public safety.

2.    Variance Notification. Any applicant to whom a variance is granted shall be given written notice that the issuance of a variance to construct a structure below the base flood elevation will result in increased premium rates for flood insurance and that such construction below the base flood elevation increases risks to life and property. Such notification and a record of all variance actions, including justification for their issuance, shall be maintained in accordance with subsection (B)(2) of this section. (Ord. 1732 § 3 (Exh. B), 2022.)

In all special flood hazard areas, the following standards shall be adhered to:

A.    Alteration of Watercourses.

1.    Require that the flood carrying capacity within the altered or relocated portion of said watercourse is maintained. Require that maintenance is provided within the altered or relocated portion of said watercourse to ensure that the flood carrying capacity is not diminished. Require compliance with CDC 27.060(B)(3)(b) and (c).

B.    Anchoring.

1.    All new construction and substantial improvements shall be anchored to prevent flotation, collapse, or lateral movement of the structure resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy.

2.    All manufactured dwellings shall be anchored per CDC 27.080(C)(4).

C.    Construction Materials and Methods.

1.    All new construction and substantial improvements shall be constructed with 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.

D.    Utilities and Equipment.

1.    Water Supply, Sanitary Sewer and On-Site Waste Disposal Systems.

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

b.    New and replacement sanitary sewage systems shall be designed to minimize or eliminate infiltration of flood waters into the systems and discharge from the systems into flood waters.

c.    On-site waste disposal systems shall be located to avoid impairment to them or contamination from them during flooding consistent with the Oregon Department of Environmental Quality.

2.    Electrical, Mechanical, Plumbing, and Other Equipment.

a.    Electrical, heating, ventilating, air conditioning, plumbing, duct systems, and other equipment and service facilities shall be elevated at or above one foot above the base flood level or shall be designed and installed to prevent water from entering or accumulating within the components and to resist hydrostatic and hydrodynamic loads and stresses, including the effects of buoyancy, during conditions of flooding. In addition, electrical, heating, ventilating, air conditioning, plumbing, duct systems, and other equipment and service facilities, if replaced as part of a substantial improvement, shall meet all the requirements of this section.

E.    Tanks.

1.    Underground tanks shall be anchored to prevent flotation, collapse and lateral movement under conditions of the base flood.

2.    Above-ground tanks shall be installed at or above one foot above the base flood level or shall be anchored to prevent flotation, collapse, and lateral movement under conditions of the base flood.

F.    Subdivision Proposals and Other Proposed Developments.

1.    All new subdivision proposals and other proposed new developments (including proposals for manufactured dwelling parks and subdivisions) greater than 50 lots or five acres, whichever is the lesser, shall include within such proposals base flood elevation data.

2.    Where base flood elevation data has not been provided or is not available from another authoritative source, it shall be generated for any land division proposal.

3.    All new subdivision proposals and other proposed new developments (including proposals for manufactured dwelling parks and subdivisions) shall:

a.    Be consistent with the need to minimize flood damage.

b.    Have public utilities and facilities such as sewer, gas, electrical, and water systems located and constructed to minimize or eliminate flood damage.

c.    Have adequate drainage provided to reduce exposure to flood hazards.

G.    Use of Other Base Flood Elevation Data.

1.    When base flood elevation data has not been provided in accordance with CDC 27.020, the local floodplain administrator shall obtain, review, and reasonably utilize any base flood elevation data available from a federal, State, or other source, in order to administer this section and CDC 27.080, 27.090, and 27.100. All new subdivision proposals and other proposed new developments (including proposals for manufactured dwelling parks and subdivisions) must meet the requirements of subsection (F) of this section.

2.    Base flood elevations shall be determined for development proposals that are five acres or more in size or are 50 lots or more, whichever is lesser, in any A zone that does not have an established base flood elevation. Development proposals located within a riverine unnumbered A zone shall be reasonably safe from flooding; the test of reasonableness includes use of historical data, high water marks, FEMA provided base level engineering data, and photographs of past flooding. When no base flood elevation data is available, the elevation requirement for development proposals within a riverine unnumbered A zone is a minimum of two feet above the highest adjacent grade, to be reasonably safe from flooding. Failure to elevate at least two feet above grade in these zones may result in higher insurance rates.

H.    Structures Located in Multiple or Partial Flood Zones. In coordination with the State of Oregon Specialty Codes:

1.    When a structure is located in multiple flood zones on the community’s flood insurance rate maps (FIRM) the provisions for the more restrictive flood zone shall apply.

2.    When a structure is partially located in a special flood hazard area, the entire structure shall meet the requirements for new construction and substantial improvements.

I.    Balanced Cut and Fill.

1.    Development, excavation, and fill shall be performed in a manner to maintain or increase flood storage and conveyance capacity and not increase design flood elevations.

2.    No net fill increase in any floodplain is allowed. All fill placed in a floodplain shall be balanced with an equal amount of soil material removal. Excavation areas shall not exceed fill areas by more than 50 percent of the square footage. Any excavation below the ordinary high water line shall not count toward compensating for fill.

3.    Excavation to balance a fill shall be located on the same lot or parcel as the fill unless it is not reasonable or practicable to do so. In such cases, the excavation shall be located in the same drainage basin and as close as possible to the fill site, so long as the proposed excavation and fill will not increase flood impacts for surrounding properties as determined through hydrologic and hydraulic analysis.

J.    Minimum Finished Floor Elevation.

1.    Minimum finished floor elevations must be at least one foot above the design flood height or highest flood of record, whichever is higher, for new habitable structures in the flood area.

K.    Other Requirements.

1.    New culverts, stream crossings, and transportation projects shall be designed as balanced cut and fill projects or designed not to significantly raise the design flood elevation. Such projects shall be designed to minimize the area of fill in flood management areas and to minimize erosive velocities. Stream crossings shall be as close to perpendicular to the stream as practicable. Bridges shall be used instead of culverts wherever practicable.

2.    Excavation and fill required for the construction of detention facilities or structures, and other facilities, such as levees, specifically shall be designed to reduce or mitigate flood impacts and improve water quality. Levees shall not be used to create vacant buildable land. (Ord. 1732 § 3 (Exh. B), 2022.)

These specific standards shall apply to all new construction and substantial improvements in addition to the general standards contained in CDC 27.070.

A.    Flood Openings.

1.    All new construction and substantial improvements with fully enclosed areas below the lowest floor (excluding basements) are subject to the following requirements:

2.    Enclosed areas below the base flood elevation, including crawl spaces, shall:

a.    Be designed to automatically equalize hydrostatic flood forces on walls by allowing for the entry and exit of floodwaters;

b.    Be used solely for parking, storage, or building access;

c.    Be certified by a registered professional engineer or architect or meet or exceed all of the following minimum criteria:

1)    A minimum of two openings,

2)    The total net area of nonengineered openings shall be not less than one square inch for each square foot of enclosed area, where the enclosed area is measured on the exterior of the enclosure walls,

3)    The bottom of all openings shall be no higher than one foot above grade,

4)    Openings may be equipped with screens, louvers, valves, or other coverings or devices provided that they shall allow the automatic flow of floodwater into and out of the enclosed areas and shall be accounted for in the determination of the net open area,

5)    All additional higher standards for flood openings in the State of Oregon Residential Specialty Codes Section R322.2.2 shall be complied with when applicable.

B.    Garages.

1.    Attached garages may be constructed with the garage floor slab below the base flood elevation (BFE) in riverine flood zones, if the following requirements are met:

a.    If located within a floodway the proposed garage must comply with the requirements of CDC 27.090.

b.    The floors are at or above grade on not less than one side;

c.    The garage is used solely for parking, building access, and/or storage;

d.    The garage is constructed with flood openings in compliance with subsection (A) of this section to equalize hydrostatic flood forces on exterior walls by allowing for the automatic entry and exit of floodwater;

e.    The portions of the garage constructed below the BFE are constructed with materials resistant to flood damage;

f.    The garage is constructed in compliance with the standards in CDC 27.070; and

g.    The garage is constructed with electrical and other service facilities located and installed so as to prevent water from entering or accumulating within the components during conditions of the base flood.

2.    Detached garages must be constructed in compliance with the standards for appurtenant structures in subsection (C)(6) of this section or nonresidential structures in subsection (C)(3) of this section depending on the square footage of the garage.

C.    For Riverine Special Flood Hazard Areas With Base Flood Elevations. In addition to the general standards listed in CDC 27.070 the following specific standards shall apply in riverine (noncoastal) special flood hazard areas with base flood elevations (BFE): zones A1-30, AH, and AE.

1.    Before Regulatory Floodway. In areas where a regulatory floodway has not been designated, no new construction, substantial improvement, or other development (including fill) shall be permitted within zones A1-30 and AE on the community’s flood insurance rate map (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.

2.    Residential Construction.

a.    New construction, conversion to, and substantial improvement of any residential structure shall have the lowest floor, including basement, elevated at or above one foot above the base flood elevation.

b.    Enclosed areas below the lowest floor shall comply with the flood opening requirements in subsection (A) of this section.

3.    Nonresidential Construction.

a.    New construction, conversion to, and substantial improvement of any commercial, industrial, or other nonresidential structure shall:

1)    Have the lowest floor, including basement, elevated at or above one foot above the base flood elevation (BFE) or, together with attendant utility and sanitary facilities:

(A)    Be floodproofed so that below 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 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 section based on their development and/or review of the structural design, specifications and plans. Such certifications shall be provided to the Floodplain Administrator as set forth in CDC 27.060(B)(2).

b.    Nonresidential structures that are elevated, not floodproofed, shall comply with the standards for enclosed areas below the lowest floor in subsection (A) of this section.

c.    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 floodproofed to the base flood level will be rated as one foot below).

4.    Manufactured Dwellings.

a.    Manufactured dwellings to be placed (new or replacement) or substantially improved that are supported on solid foundation walls shall be constructed with flood openings that comply with subsection (A) of this section.

b.    The bottom of the longitudinal chassis frame beam shall be at or above base flood elevation.

c.    Manufactured dwellings to be placed (new or replacement) or substantially improved shall be anchored to prevent flotation, collapse, and lateral movement during the base flood. 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).

d.    Electrical crossover connections shall be a minimum of 12 inches above base flood elevation (BFE).

5.    Recreational Vehicles. Recreational vehicles placed on sites are required to:

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 jacking system, is attached to the site only by quick disconnect type utilities and security devices, and has no permanently attached additions; or

c.    Meet the requirements of subsection (C)(4) of this section, including the anchoring and elevation requirements for manufactured dwellings.

6.    Appurtenant (Accessory) Structures. Relief from elevation or floodproofing requirements for residential and nonresidential structures in riverine (noncoastal) flood zones may be granted for appurtenant structures that meet the following requirements:

a.    Appurtenant structures located partially or entirely within the floodway must comply with requirements for development within a floodway found in CDC 27.090.

b.    Appurtenant structures must only be used for parking, access, and/or storage and shall not be used for human habitation.

c.    In compliance with State of Oregon Specialty Codes, appurtenant structures on properties that are zoned residential are limited to one-story structures less than 200 square feet, or 400 square feet if the property is greater than two acres in area and the proposed appurtenant structure will be located a minimum of 20 feet from all property lines. Appurtenant structures on properties that are zoned as nonresidential are limited in size to 120 square feet.

d.    The portions of the appurtenant structure located below the base flood elevation must be built using flood resistant materials.

e.    The appurtenant structure must be adequately anchored to prevent flotation, collapse, and lateral movement of the structure resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy, during conditions of the base flood.

f.    The appurtenant structure must be designed and constructed to equalize hydrostatic flood forces on exterior walls and comply with the requirements for flood openings in subsection (A) of this section.

g.    Appurtenant structures shall be located and constructed to have low damage potential.

h.    Appurtenant structures shall not be used to store toxic material, oil, or gasoline, or any priority persistent pollutant identified by the Oregon Department of Environmental Quality unless confined in a tank installed in compliance with CDC 27.070(E).

i.    Appurtenant structures shall be constructed with electrical, mechanical, and other service facilities located and installed so as to prevent water from entering or accumulating within the components during conditions of the base flood.

7.    Below-Grade Crawl Spaces.

a.    The building must be designed and adequately anchored to resist flotation, collapse, and lateral movement of the structure resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy. Hydrostatic loads and the effects of buoyancy can usually be addressed through the required flood openings stated in subsection (A) of this section. Because of hydrodynamic loads, crawlspace construction is not allowed in areas with flood velocities greater than five feet per second unless the design is reviewed by a qualified design professional, such as a registered architect or professional engineer. Other types of foundations are recommended for these areas.

b.    The crawlspace is an enclosed area below the base flood elevation (BFE) and, as such, must have openings that equalize hydrostatic pressures by allowing the automatic entry and exit of floodwaters. The bottom of each flood vent opening can be no more than one foot above the lowest adjacent exterior grade.

c.    Portions of the building below the BFE must be constructed with materials resistant to flood damage. This includes not only the foundation walls of the crawlspace used to elevate the building, but also any joists, insulation, or other materials that extend below the BFE. The recommended construction practice is to elevate the bottom of joists and all insulation above BFE.

d.    Any building utility systems within the crawlspace must be elevated above BFE or designed so that floodwaters cannot enter or accumulate within the system components during flood conditions. Ductwork, in particular, must either be placed above the BFE or sealed from floodwaters.

e.    The interior grade of a crawlspace below the BFE must not be more than two feet below the lowest adjacent exterior grade.

f.    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. The height limitation is the maximum allowable unsupported wall height according to the engineering analyses and building code requirements for flood hazard areas.

g.    There must be an adequate drainage system that removes floodwaters 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.

h.    The velocity of floodwaters at the site shall 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. 1732 § 3 (Exh. B), 2022.)

Located within the special flood hazard areas established in CDC 27.020(A) are areas designated as floodways. Since the floodway is an extremely hazardous area due to the velocity of the floodwaters which carry debris, potential projectiles, and erosion potential, the following provisions apply:

A.    Prohibit encroachments, including fill, new construction, substantial improvements, and other development within the adopted regulatory floodway unless:

1.    Certification by a registered professional civil engineer is provided demonstrating through hydrologic and hydraulic analyses performed in accordance with standard engineering practice that the proposed encroachment shall not result in any increase in flood levels within the community during the occurrence of the base flood discharge; or

2.    A community may permit encroachments within the adopted regulatory floodway that would result in an increase in base flood elevations; provided, that a conditional letter of map revision (CLOMR) is applied for and approved by the Federal Insurance Administrator, and the requirements for such revision as established under 44 CFR 65.12 are fulfilled.

B.    If the requirements of subsection (A) of this section are satisfied, all new construction, substantial improvements, and other development shall comply with all other applicable flood hazard reduction provisions of CDC 27.070, 27.080, this section, and CDC 27.100. (Ord. 1732 § 3 (Exh. B), 2022.)

Shallow flooding areas appear on FIRMs as AO zones with depth designations or as AH zones with base flood elevations. For AO zones the base flood depths 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. For both AO and AH zones, adequate drainage paths are required around structures on slopes to guide floodwaters around and away from proposed structures.

A.    Standards for AH Zones. Development within AH zones must comply with the standards in CDC 27.070, 27.080, 27.090, and this section.

B.    Standards for AO Zones. In AO zones, the following provisions apply in addition to the requirements in CDC 27.070 and this section.

1.    New construction, conversion to, and substantial improvement of residential structures and manufactured dwellings within AO zones shall have the lowest floor, including basement, elevated above the highest grade adjacent to the building, at minimum to or above the depth number specified on the flood insurance rate maps (FIRM) or at least two feet if no depth number is specified. For manufactured dwellings the lowest floor is considered to be the bottom of the longitudinal chassis frame beam.

2.    New construction, conversion to, 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, at minimum to or above the depth number specified on the flood insurance rate maps (FIRMS) or 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 the depth number specified on the FIRM or a minimum of two feet above the highest adjacent grade if no depth number is specified, 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 the effects of buoyancy. If this method is used, compliance shall be certified by a registered professional engineer or architect as stated in CDC 27.080(C)(3)(a)(1)(C).

3.    Recreational vehicles placed on sites within AO zones on the community’s flood insurance rate maps (FIRM) shall 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 jacking system, is attached to the site only by quick disconnect type utilities and security devices, and has no permanently attached additions; or

c.    Meet the elevation requirements of subsection (B)(1) of this section, and the anchoring and other requirements for manufactured dwellings of CDC 27.080(C)(4).

4.    In AO zones, new and substantially improved appurtenant structures must comply with the standards in CDC 27.080(C)(6).

5.    In AO zones, enclosed areas beneath elevated structures shall comply with the requirements in CDC 27.080(A). (Ord. 1732 § 3 (Exh. B), 2022.)

Where the provisions of this chapter are less restrictive or conflict with comparable provisions of this code, regional, State, or federal law, the provisions that are more restrictive shall govern. Where this chapter imposes restrictions that are more stringent than regional, State and federal law, the provisions of this chapter shall govern. (Ord. 1732 § 3 (Exh. B), 2022. Formerly 27.170.)