A. General Standards: In all areas of special flood hazards, the following standards are required:
1. Anchoring:
a. All new construction and substantial improvements shall be anchored to prevent flotation, collapse, or lateral movement of the structure.
b. All manufactured homes must likewise be anchored to prevent flotation, collapse, or lateral movement, and shall be installed using methods and practices that minimize flood damage. Anchoring methods may include, but are not limited to, use of over the top or frame ties to ground anchors (reference FEMA's "Manufactured Home Installation In Flood Hazard Areas" guidebook for additional techniques).
2. AH Zone Drainage: Adequate drainage paths are required around structures on slopes to guide floodwaters around and away from proposed structures.
3. 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.
4. Utilities:
a. All new and replacement water supply systems shall be designed to minimize or eliminate infiltration of floodwaters into the system;
b. New and replacement sanitary sewage systems shall be designed to minimize or eliminate infiltration of floodwaters into the systems and discharge from the systems into floodwaters; and
c. On site waste disposal systems shall be located to avoid impairment to them or contamination from them during flooding.
5. Subdivision Proposals:
a. All subdivision proposals shall be consistent with the need to minimize flood damage;
b. All subdivision proposals shall have utilities and facilities such as sewer, gas, electrical, and water systems located and constructed to minimize or eliminate flood damage;
c. All subdivision proposals shall have adequate drainage provided to reduce exposure to flood damage; and
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 fifty (50) lots or five (5) acres (whichever is less).
6. Review Of Building Permits: Where flood protection elevation data is not available either through the flood insurance study, FIRM, or from another authoritative source (subsection 12-1-4C2 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 use of historical data, high water marks, photographs of past flooding, etc., where available. Failure to elevate at least two feet (2') above grade in these zones may result in higher insurance rates.
B. Specific Standards: In all areas of special flood hazards where flood protection elevation data has been provided as set forth in section 12-1-2, "Definitions", and subsection 12-1-3B, "Basis For Establishing The Areas Of Special Flood Hazard", or subsection 12-1-4C2, "Use Of Other Base Flood Data (In A Zones)" 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 at or above the flood protection elevation.
b. Fully enclosed areas below the lowest floor that are subject to flooding are prohibited, or shall be designed to automatically equalize hydrostatic flood forces on exterior walls by allowing for the entry and exit of floodwaters. Designs for meeting this requirement 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 (2) 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 (1') 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 floodwaters.
(4) Below grade crawl spaces are prohibited at sites where the velocity of floodwaters exceeds five feet (5') per second.
(5) All building utility systems within the crawl space shall be elevated above flood protection elevation or be designed so that floodwaters cannot enter or accumulate within the system component during flood conditions.
(6) The interior of a crawl space below the flood protection elevation must not be more than two feet (2') below the lowest adjacent exterior grade (LAG) and the height of the below grade crawl space, measured from the interior grade of the crawl space to the top of the crawl space foundation must not exceed four feet (4') at any point.
(7) Below grade crawl spaces constructed in accordance with the requirements listed in this subsection shall not be considered basements. However, applicants who construct buildings that have below grade crawl spaces are hereby advised that such buildings will have higher flood insurance premiums than buildings that have crawl spaces with interior elevations at or above the lowest adjacent grade.
2. Nonresidential Construction: New construction and substantial improvement of any commercial, industrial or other nonresidential structure shall either have the lowest floor, including basement, elevated at or above the flood protection elevation or, together with attendant utility and sanitary facilities, shall:
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 subsection based on their development and/or review of the structural design, specifications and plans. Such certifications shall be provided to the official as set forth in subsection 12-1-4C3b of this chapter;
d. Nonresidential structures that are elevated, not floodproofed, must meet the same standards for space below the lowest floor as described in subsection B1b of this section;
e. Applicants floodproofing nonresidential buildings shall be notified that flood insurance premiums will be based on rates that are one foot (1') below the floodproofed level (e.g., a building floodproofed to the base flood level will be rated as 1 foot below).
3. Manufactured Homes:
a. All manufactured homes to be placed or substantially improved on sites:
(1) Outside of a manufactured home park or subdivision,
(2) In a new manufactured home park or subdivision,
(3) In an expansion to an existing manufactured home park or subdivision, or
(4) In an existing manufactured home park or subdivision on which a manufactured home has incurred "substantial damage" as the result of a flood; shall be elevated on a permanent foundation such that the lowest floor of the manufactured home is elevated at or above the flood protection elevation and be securely anchored to an adequately designed foundation system to resist flotation, collapse and lateral movement.
b. Manufactured homes to be placed or substantially improved on sites in an existing manufactured home park or subdivision within zones AH and AE on the community's FIRM that are not subject to the above manufactured home provisions must be elevated so that either:
(1) The lowest floor of the manufactured home is elevated at or above the flood protection elevation, or
(2) The manufactured home chassis is supported by reinforced piers or other foundation elements of at least equivalent strength that are no less than thirty six inches (36") in height above grade and be securely anchored to an adequately designed foundation system to resist flotation, collapse, and lateral movement.
4. Recreational Vehicles: Recreational vehicles placed on sites are required to either:
a. Be on the site for fewer than one hundred eighty (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 subsection B3 of this section and the elevation and anchoring requirements for manufactured homes.
C. Before Regulatory Floodway: In areas where a regulatory floodway has not been designated: No new construction, substantial improvements, or other development (including fill) shall be permitted within the AE zone on the community's FIRM, unless it is demonstrated that the cumulative effect of the proposed development, when combined with all other existing and anticipated development, will not increase the water surface elevation of the base flood more than one foot (1') at any point within the community.
D. Floodways: Located within areas of special flood hazard established in subsection 12-1-3B of this chapter are areas designated as floodways. Since the floodway is an extremely hazardous area due to the velocity of floodwaters which carry debris, potential projectiles, and erosion potential, the following provisions apply:
1. Prohibit encroachments, including fill, new construction, substantial improvements, and other development unless certification by a registered professional civil engineer is provided demonstrating through hydrologic and hydraulic analyses performed in accordance with standard engineering practice that encroachments shall not result in any increase in flood levels during the occurrence of the base flood discharge.
2. If subsection D1 of this section is satisfied, all new construction and substantial improvements shall comply with all applicable flood hazard reduction provisions of this section.
E. Standards For Shallow Flooding Areas (AO Zones): Shallow flooding areas appear on FIRMs as AO zones with depth designations. The base flood depths in these zones range from one to three feet (3') aboveground where a clearly defined channel does not exist, or where the path of flooding is unpredictable and where velocity flow may be evident. Such flooding is usually characterized as sheet flow. In these areas, the following provisions apply:
1. New construction and substantial improvements of residential structures and manufactured homes within AO zones shall have the lowest floor (including basement) elevated above the highest grade adjacent to the building, one foot (1') or more above the depth number specified on the FIRM (at least 2 feet above highest adjacent grade if no depth number is specified).
2. New construction and substantial improvements of nonresidential structures within AO zones shall either:
a. Have the lowest floor (including basement) elevated above the highest adjacent grade of the building site, one foot (1') or more above the depth number specified on the FIRM (at least 2 feet if no depth number is specified); or
b. Together with attendant utility and sanitary facilities, be completely floodproofed to or above that level so that any space below that level is watertight with walls substantially impermeable to the passage of water and with structural components having the capability of resisting hydrostatic and hydrodynamic loads and effects of buoyancy. If this method is used, compliance shall be certified by a registered professional engineer or architect as in subsection B2c of this section.
3. Require adequate drainage paths around structures on slopes to guide floodwaters around and away from proposed structures.
4. Critical facilities shall have the lowest floor, including basement, elevated three feet (3') above the depth specified on the FIRM or at least five feet (5') above highest adjacent grade if no depth number is specified.
F. 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 (3') above the base flood elevation 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 flood protection elevation shall be provided to all critical facilities to the extent possible. (Ord. 529, 11-2-2009)
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