157.159 Provisions for flood hazard reduction.
(A) General standards. In all areas of special flood hazards, the following provisions are required.
(1) Anchoring.
(a) All new construction and substantial improvements shall be anchored to prevent flotation, collapse or lateral movement of the structure.
(b) All manufactured commercial structures and homes must likewise be anchored to prevent flotation, collapse or lateral movement and shall be installed using methods and practices that minimize flood damage.
(c) Anchoring methods may include, but are not limited to, the 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).
(2) Construction materials and methods.
(a) All new construction and substantial improvements shall be constructed with materials and utility equipment resistant to flood damage.
(b) All new construction and substantial improvements shall be constructed using methods and practices that minimize flood damage.
(c) Electrical, heating, ventilation, plumbing and air-conditioning equipment and other service facilities shall be designed and/or otherwise elevated or located so as to prevent water from entering or accumulating within the components during conditions of flooding.
(3) Utilities. All new and replacement water supply systems shall be designed to minimize or eliminate infiltration of flood waters into the system.
(a) 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.
(b) On-site waste disposal systems shall be located to avoid impairment to them or contamination from them during flooding.
(4) Subdivision proposals.
(a) All subdivision proposals shall be consistent with the need to minimize flood damage.
(b) All subdivision proposals shall have public utilities and facilities such as sewer, gas, electrical and water systems located and constructed to minimize flood damage.
(c) All subdivision proposals shall have adequate drainage provided to reduce exposure to flood damage.
(d) Where base flood elevation data has not been provided or is not available from another authoritative source, it shall be generated for subdivision proposals and other proposed developments which contain at least 50 lots or five acres, whichever is less.
(5) Review of building permits.
(a) Where elevation data is not available either through the Flood Insurance Study or from another authoritative source (§ 157.158(C) of this chapter), applications for building permits shall be reviewed to assure that proposed construction will be reasonably safe from flooding. The test of reasonableness is a local judgment and includes the use of historical data, high water marks, photographs of past flooding and the like, where available.
(b) Failure to elevate at least two feet above grade in these zones may result in higher insurance rates.
(B) Specific standards. In all areas of special flood hazards where base flood elevation data has been provided as set forth in §§ 157.157(B) and 157.158(C) of this chapter, the following provisions are required.
(1) Residential construction.
(a) New construction and substantial improvement of any residential structure shall have the lowest floor, including basement, elevated to two feet above base flood elevation.
(b) Fully enclosed areas below the lowest floor that are subject to flooding are prohibited, or shall be designed to automatically equalize hydrostatic flood forces on exterior walls by allowing for the entry and exit of 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.
(1) 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.
(2) The bottom of all openings shall be no higher than one foot above grade.
(3) Openings may be equipped with screens, louvers or other coverings or devices provided that they permit the automatic entry and exit of flood waters.
(2) Non-residential construction. New construction and substantial improvement of any commercial, industrial or other non-residential structure shall have either the lowest floor, including basement, elevated to two feet above the base flood elevation; or together with the attendant utility and sanitary facilities, shall:
(a) Be flood-proofed so that below the base flood level the structure is water-tight 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 division (B) based on their development and/or review of the structural design, specifications and plans. Such certification shall be provided to the official as set forth in § 157.158(C) of this chapter.
(d) Non-residential structures that are elevated, but not flood-proofed, must meet the same standards for space below the lowest floor as described in division (B)(1)(b) above.
(e) Applicants flood-proofing non-residential buildings shall be notified that flood insurance premiums will be based on rates that are one foot below the flood-proofed level (e.g., a building constructed to the base flood level will be rated as one foot below that level).
(3) Manufactured Commercial Structures and Homes. All manufactured commercial structures and homes to be placed or substantially improved within Zones Al-A30 and AE shall be elevated on a permanent foundation such that the lowest floor of the manufactured home is two feet above base flood elevation and be securely anchored to an adequately anchored foundation system in accordance with the provisions of divisions (A)(1)(b) and (A)(1)(c) above. Electrical crossover connections shall be a minimum of 12 inches above the base flood elevation. Crossover ducts are allowed below BFE, but shall be constructed to prevent floodwaters from entering or accumulating within system components. This may require an engineer’s certification. Manufactured dwellings placed on solid foundation walls shall be constructed with flood openings that comply with 5.1-2 of the Oregon model ordinance. Within Zones A1-A30 and AE without a designated floodway, new development shall not be permitted unless it is demonstrated that the cumulative effect of all past and projected development will not increase the BFE by more than one foot.
(4) Height measurements. For all construction in a FHO – Flood Hazard Overlay Zone, all building height restrictions shall be calculated as starting two feet above the base flood elevation.
(5) Recreational vehicles. Recreational vehicles placed on sites are required to either:
(a) Be on the site for fewer than 180 consecutive days;
(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 division (B)(3) above and the elevation and anchoring requirements for manufactured homes.
(6) 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 constructed within the SFHA shall have the lowest floor elevated three feet above BFE or to the height of the 500-year flood, whichever is higher. Access to and from the critical facility should also be protected to the height utilized above. Flood-proofing 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.
(C) Floodways.
(1) Located within areas of special flood hazard established in § 157.157(B) of this chapter are areas designated as floodways.
(2) Since the floodway is an extremely hazardous area due to the velocity of flood waters which carry debris, potential projectiles and erosion potential, the following provisions apply:
(a) Prohibit encroachments, including fill, new construction, substantial improvements and other development unless certification by a registered professional engineer or architect is provided demonstrating that encroachments shall not result in any increase in flood levels during the occurrence of base flood discharge; and
(b) If division (C)(2)(a) above is satisfied, all new construction and substantial improvements shall comply with all applicable flood hazard reduction provisions of this section.
(c) Within six months the city shall notify FEMA of changes in the base flood elevation by submitting technical or scientific data so insurance and floodplain management can be based on current data per 44 CFR 60.3(b) and 65.3 and Oregon Model Ordinance 4.3-5. (Ord. 80-2, passed 06/14/2010; Ord. 2013-01, passed 08/12/2013; Ord. 2018-02, passed 09/10/2018)