The purpose of this chapter is 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:

Protect human life and health;

Minimize expenditure of public money for costly flood control projects;

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

Minimize prolonged business interruptions;

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

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;

Notify potential buyers that the property is in an area of special flood hazard;

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

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

(Ord. 23-09, 12/12/2023)

§ 9.10.020 Definitions.

Unless specifically defined below, words or phrases used in this chapter shall be interpreted so as to give them the meaning they have in common usage. These definitions are only applicable to this chapter and Tigard Community Development Code (TCDC) Chapter 18.510, Sensitive Lands.

"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"

means a designated Zone AO, AH, AR/AO or AR/AH (or VO) on the city's Flood Insurance Rate Map (FIRM) with a one percent or greater annual chance of flooding to an average depth of one to three feet where a clearly defined channel does not exist, where the path of flooding is unpredictable, and where velocity flow may be evident. Such flooding is characterized by ponding or sheet flow.

"Area of special flood hazard"

means the land in the floodplain within the city 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. "Special flood hazard area" is synonymous in meaning and definition with the phrase "area of special flood hazard."

"Base flood"

means a flood having a one percent chance of being equaled or exceeded in any given year.

"Base flood elevation (BFE)"

means the elevation to which floodwater 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.

"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; new and replacement bridges; hospitals; police, fire, and emergency response installations; and installations that produce, use, or store hazardous materials or hazardous waste.

"Development"

means any man-made 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.

"Flood" or "flooding"

means:

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

The overflow of inland or tidal waters;

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

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.

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.

See "Flood Insurance Study."

"Flood Insurance Rate Map (FIRM)"

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

"Flood Insurance Study (FIS)"

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) or flood-related erosion hazards.

"Flood proofing"

means any combination of structural and nonstructural additions, changes, or adjustments to structures which reduce or eliminate risk of flood damage to real estate or improved real property, water and sanitary facilities, structures, and their contents.

"Floodway"

means the channel of a river or other watercourse and the adjacent land areas that must be reserved in order to discharge the base flood without cumulatively increasing the water surface elevation more than one foot. 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 structure.

"Historic structure"

means any structure that is:

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;

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;

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

Individually listed on a City of Tigard Historic Resources list acknowledged by the Secretary of the Interior.

"Lowest floor"

means the lowest floor of the lowest enclosed area (including basement). An unfinished or flood resistant enclosure, usable solely for parking of vehicles, building access or storage in an area other than a basement area is not considered a building's lowest floor, provided that such enclosure is not built so as to render the structure in violation of the applicable non-elevation design requirements of this chapter.

"Manufactured dwelling"

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 dwelling" does not include a "recreational vehicle" and is synonymous with "manufactured home."

"Manufactured dwelling park or subdivision"

means a parcel (or contiguous parcels) of land divided into two or more manufactured dwelling lots for rent or sale.

"Mean sea level"

means, for purposes of the National Flood Insurance Program, the National Geodetic Vertical Datum (NGVD) of 1929 or other datum, to which base flood elevations shown on the city's Flood Insurance Rate Map are referenced.

"New construction"

means, for floodplain management purposes, structures for which the "start of construction" commenced on or after the effective date of a floodplain management regulation adopted by City of Tigard and includes any subsequent improvements to such structures.

"Recreational vehicle"

means a vehicle which is:

Built on a single chassis;

400 square feet or less when measured at the largest horizontal projection;

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

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

Special Flood Hazard Area.

See "Area of special flood hazard" for this definition.

"Start of construction"

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

"Structure"

means, for floodplain management purposes, a walled and roofed building, including a gas or liquid storage tank, that is principally above ground, as well as a manufactured dwelling.

"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% 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% 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:

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 code enforcement official and which are the minimum necessary to assure safe living conditions; or

Any alteration of a "historic structure," provided that the alteration will not preclude the structure's continued designation as a "historic structure."

"Violation"

means the failure of a structure or other development to be fully compliant with the city's floodplain management regulations. A structure or other development without the elevation certificate, other certifications, or other evidence of compliance required in this chapter is presumed to be in violation until such time as that documentation is provided.

(Ord. 23-09, 12/12/2023)

§ 9.10.030 Applicability.

All development within areas of special flood hazard is subject to the terms of this chapter and is required to comply with its provisions and all other applicable regulations including, but not limited to, TCDC Chapter 18.510, Sensitive Lands.

The areas of special flood hazard identified by FEMA in a scientific and engineering report entitled "The Flood Insurance Study for Washington County, Oregon and Incorporated Areas effective October 19, 2018" with accompanying Flood Insurance Map (FIRM Panels: 41067C0529F, 41067C0533E, 41067C0534E, 41067C0541E through 41067C0544E, and 41067C0563E) is hereby adopted by reference and declared to be a part of this chapter.

(Ord. 23-09, 12/12/2023)

§ 9.10.040 General Provisions.

Coordination with State of Oregon Specialty Codes. Pursuant to the requirement established in ORS 455 that the City of Tigard administers and enforces the State of Oregon Specialty Codes, the City of Tigard does hereby acknowledge that the Oregon Specialty Codes contain certain provisions that apply to the design and construction of buildings and structures located in areas of special flood hazard. Therefore, this chapter is intended to be administered and enforced in conjunction with the Oregon Specialty Codes.

Warning. The degree of flood protection required by this chapter is considered reasonable for regulatory purposes and is based on scientific and engineering considerations. Larger floods can and will occur on rare occasions. Flood heights may be increased by man-made 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.

Permit Review. The duties of the Floodplain Administrator, or their designee, shall include, but not be limited to, review all development permits to determine that:

The permit requirements of this ordinance have been satisfied;

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

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 are met;

Review all development permits to determine if the proposed development is located in an area where base flood elevation data is available either through the Flood Insurance Study or from another authoritative source. If base flood elevation data is not available then ensure compliance with the provisions of Section 9.10.050.J;

Provide to building officials the base flood elevation applicable to any building requiring a development permit;

Review all development permit applications to determine if the proposed development qualifies as a substantial improvement as defined by Section 9.10.020;

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 Section 9.10.050.C; and

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

Information to be Obtained and Maintained. The following information shall be obtained and maintained and shall be made available for public inspection as needed:

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 data is provided through the Flood Insurance Study, Flood Insurance Rate Map, or obtained in accordance with Section 9.10.050.J.

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 Section 9.10.050.N are adhered to and all other required local, state, and federal permits have been obtained and approved.

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).

Where base flood elevation data are utilized, obtain record drawing 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.

Maintain all elevation certificates submitted to the City of Tigard.

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 data is provided through the FIS, FIRM, or obtained in accordance with Section 9.10.050.J.

Maintain all floodproofing certificates required under this chapter.

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

Obtain and maintain all hydrologic and hydraulic analyses performed as required under Section 9.10.050.N.

10.

Record and maintain all substantial improvement and substantial damage calculations and determinations as required under subsection H.

11.

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

City Boundary Alterations. The Floodplain Administrator shall notify the Federal Insurance Administrator in writing whenever the boundaries of the city have been modified by annexation or the city 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 and Flood Insurance Rate Maps accurately represent the city's boundaries. The notification will include a copy of a map of the city suitable for reproduction, clearly delineating the new corporate limits or new area for which the city has assumed or relinquished floodplain management regulatory authority.

Watercourse Alterations. The Floodplain Administrator shall 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 along with either a proposed maintenance plan to assure the flood carrying capacity within the altered or relocated portion of the watercourse is maintained; or 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 when required under subsection G to ensure compliance with all applicable requirements in subsection G and Section 9.10.050.C.

Requirement to Submit New Technical Data. The city'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, the city must notify the Federal Insurance Administrator of the changes by submitting technical or scientific data in accordance with Title 44 of the Code of Federal Regulations (CFR), Section 65.3. The city 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 process. The Floodplain Administrator shall require a Conditional Letter of Map Revision prior to the issuance of a floodplain development permit for proposed floodway encroachments that increase the base flood elevation and 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 from FEMA. This notification to FEMA shall be provided as a Letter of Map Revision.

Substantial Improvement and Substantial Damage Assessments and Determinations. The Floodplain Administrator shall:

Conduct substantial improvement (as defined in Section 9.10.020) reviews for all structural development proposal applications and maintain a record of Substantial Improvement calculations within permit files in accordance with subsection D.

Conduct substantial damage assessments when structures are damaged due to a natural hazard event or other causes.

Make substantial damage determinations whenever structures within the area of special flood hazard (as established in Section 9.10.030.B) are damaged to the extent that the cost of restoring the structure to its before damaged condition would equal or exceed 50% of the market value of the structure before the damage occurred.

Floodplain Development Permit Required. A development permit shall be obtained before construction or development begins within any area horizontally within the area of special flood hazard established in Section 9.10.030.B. The development permit shall be required for all structures, including manufactured dwellings, and for all other development, as defined in Section 9.10.020, including fill and other development activities.

Application for Development Permit. 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:

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 D;

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

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 Section 9.10.050.M.3;

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

Base flood elevation data for subdivision proposals or other development when required by this chapter;

Substantial improvement calculation for any improvement, addition, reconstruction, renovation, or rehabilitation of an existing structure; and

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

Severability. 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.

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

(Ord. 23-09, 12/12/2023)

§ 9.10.050 National Flood Insurance Program General Standards.

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

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

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

Alteration of Watercourses. The Floodplain Administrator shall require that the flood carrying capacity within the altered or relocated portion of said watercourse is maintained and that maintenance is provided within the altered or relocated portion of said watercourse to ensure that the flood carrying capacity is not diminished. Compliance with Section 9.10.040.F and G.

Anchoring. 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. All manufactured dwellings shall be anchored in accordance with subsection M.4.

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

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

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.

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

Electrical, Mechanical, Plumbing, and Other Equipment. Electrical, heating, ventilating, air-conditioning, plumbing, duct systems, and other equipment and service facilities shall be elevated at or 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 shall, if replaced as part of a substantial improvement, meet all the requirements of this section.

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

Critical Facilities. Construction of new critical facilities must be, to the extent practicable, located outside areas of special flood hazard.

Construction of new critical facilities, other than critical bridges, are allowed within areas of special flood hazard if no feasible alternative site is available and the following applicable criteria are met:

Critical facilities constructed within areas of special flood hazard must have the lowest floor elevated three feet above base flood elevation or to the height of the 500-year flood, whichever is higher.

To the extent practicable, access to and from the critical facility should also be protected to three feet above base flood elevation 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 floodwaters.

All new and replacement critical bridges must have the lowest extension of the bridge superstructure elevated three feet above base flood elevation or to the height of the 500-year flood, whichever is higher.

Where standard subsection H.2 cannot be met, an analysis of alternative bridge designs is required by a registered professional civil engineer. The proposed encroachment will result in the least impact to base flood levels in the area of special flood hazard of the practicable alternative bridge designs — as demonstrated through hydrologic and hydraulic analyses performed in accordance with standard engineering practice.

Subdivision Proposals.

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.

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

Be consistent with the need to minimize flood damage;

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

Have adequate drainage provided to reduce exposure to flood hazards.

Use of Other Base Flood Data. When base flood elevation data has not been provided in accordance with Section 9.10.030.B 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 Section 9.10.050. All new subdivision proposals and other proposed new developments (including proposals for manufactured dwelling parks and subdivisions) must meet the requirements of subsection I. 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, etc. 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.

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

When a structure is located in multiple flood zones on the city's pertinent Flood Insurance Rate Maps (FIRMs) the provisions for the more restrictive flood zone shall apply.

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

Specific Standards for Riverine (Including All Non-Coastal) Flood Zones. These specific standards shall apply to all new construction and substantial improvements in addition to the general standards contained in subsections A through K.

Flood Openings. All new construction and substantial improvements with fully enclosed areas below the lowest floor (excluding basements) are subject to the following requirements. Enclosed areas below the base flood elevation, including crawl spaces shall:

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

Be used solely for parking, storage, or building access; and

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

A minimum of two openings,

ii.

The total net area of non-engineered 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,

iii.

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

iv.

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, and

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.

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

If located within a floodway the proposed garage must comply with the requirements of subsection N;

The floors are at or above grade on at least than one side;

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

The garage is constructed with flood openings in compliance with subsection L.1 to equalize hydrostatic flood forces on exterior walls by allowing for the automatic entry and exit of floodwater;

The portions of the garage constructed below the base flood elevation are constructed with materials resistant to flood damage;

The garage is constructed in compliance with the general standards subsections A through K; and

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.

Detached Garages. Detached garages must be constructed in compliance with the standards for appurtenant structures in subsection M.6 or nonresidential structures in subsection M.3 depending on the square footage of the garage.

For Riverine (Non-Coastal) Areas of Special Flood Hazard with Base Flood Elevations. In addition to the general standards in subsections A through K, the following specific standards shall apply in riverine (non-coastal) areas of special flood hazard with base flood elevations: Zones A1-A30, AH, and AE:

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 city'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 at any point within the city.

Residential Construction.

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

Enclosed areas below the lowest floor shall comply with the flood opening requirements in subsection L.1.

Nonresidential Construction.

New construction, conversion to, and substantial improvement of, any commercial, industrial, or other nonresidential structure shall have the lowest floor, including basement, elevated at one foot above the base flood elevation. Or, together with attendant utility and sanitary facilities:

Be floodproofed so that below the base flood level the structure is watertight with walls substantially impermeable to the passage of water;

ii.

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

iii.

Be certified by a registered professional engineer or architect that the design and methods of construction are in accordance with accepted standards of practice for meeting provisions of this section based on their development or review of the structural design, specifications and plans. Such certifications shall be provided to the Floodplain Administrator as set forth Section 9.10.040.D.

Nonresidential structures that are elevated, not floodproofed, shall comply with the standards for enclosed areas below the lowest floor in subsection L.1.

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.

Manufactured Dwellings.

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 L.1;

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

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); and

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

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

Be on the site for fewer than 180 consecutive days; and

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

Meet the requirements of subsection M.4, including the anchoring and elevation requirements for manufactured dwellings.

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

Appurtenant structures located partially or entirely within the floodway must comply with requirements for development within a floodway found in subsection N;

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

Appurtenant structures on properties are limited to one-story structures less than 600 square feet in A zones and must meet applicable setbacks from property lines;

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

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;

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 L.1;

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

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 incompliance with subsection G; and

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.

Floodways. Located within the areas of special flood hazard established in Section 9.10.030.B are areas designated as floodways. Because 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:

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

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 city during the occurrence of the base flood discharge; or

A city 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 is applied for and approved by the Federal Insurance Administrator, and the requirements for such revision as established under Volume 44 of the Code of Federal Regulations, Section 65.12 are fulfilled.

If the requirements of subsection N.1 are satisfied, all new construction, substantial improvements, and other development shall comply with all other applicable flood hazard reduction provisions of Section 9.10.050.

Standards for Shallow Flooding Areas. 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.

Standards for AH Zones. Development within AH Zones must comply with the standards in subsections A through O.

Standards for AO Zones. In AO zones, the following provisions apply in addition to the requirements in subsections A through K and O.

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 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.

New construction, conversion to, and substantial improvements of nonresidential structures within AO Zones shall either:

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 or at least two feet if no depth number is specified; or

ii.

Together with attendant utility and sanitary facilities, be completely floodproofed to or above the depth number specified on the Flood Insurance Rate Map 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 subsection M.3.a.iii.

Recreational vehicles placed on sites within AO Zones on the city's Flood Insurance Rate Maps shall either:

Be on the site for fewer than 180 consecutive days; and

ii.

iii.

Meet the elevation requirements of subsection O.2.a, and the anchoring and other requirements for manufactured dwellings of subsection M.4.

In AO Zones, new and substantially improved appurtenant structures must comply with the standards in subsection M.6.

In AO zones, enclosed areas beneath elevated structures shall comply with the requirements in subsection L.1.

(Ord. 23-09, 12/12/2023)

§ 9.10.060 Violations.

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, including, but not limited to, TCDC Chapter 18.510, Sensitive Lands. 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 Class 1 civil infraction, processed according to the procedures in the civil infractions ordinance, set out in TMC Chapter 1.16. Each violation of a separate provision of this chapter shall constitute a separate infraction, and each day that a violation of this chapter is committed or permitted to continue shall constitute a separate infraction. A finding of a violation of this chapter shall not relieve the responsible party of the duty to abate the violation. The penalties imposed by this section are in addition and not in lieu of any remedies available to the city. If a provision of this chapter is violated by a firm or corporation, the officer or officers, or person or persons responsible for the violation shall be subject to the penalties imposed by this chapter. Nothing contained herein shall prevent the City of Tigard from taking such other lawful action as is necessary to prevent or remedy any violation.

(Ord. 23-09, 12/12/2023)