(A) Residential structures.
(1) In Zones A, AE, A1-30, and AH, all new construction and substantial improvements shall have the lowest floor, including basement, elevated to or above one foot above the base flood elevation.
(2) In Zone AO, all new construction and substantial improvements shall have the lowest floor, including basement, elevated above the highest adjacent grade at least as high as one foot above the depth number specified in feet on the FIRM or if no depth number is specified on the FIRM, at least as high as two feet plus one foot of free board.
(3) In the floodway, new structures for human habitation are prohibited.
(B) Nonresidential structures.
(1) In Zones A, AE, A1-30, and AH, all new construction and substantial improvements shall have the lowest floor, including basement, elevated to or above one foot above the base flood elevation.
(2) In Zone AO, all new construction and substantial improvements shall have the lowest floor elevated above the highest adjacent grade at least as high as one foot above the depth number specified in feet on the FIRM or if no depth number is specified on the FIRM, at least as high as two feet plus one foot of freeboard.
(C) Wet-floodproofing for agricultural structures by variance. When owners elect to wet floodproof agricultural structures, the structure shall:
(1) Be anchored to resist flotation, collapse, and lateral movement.
(2) Have flood damage-resistant materials below the base flood elevation in compliance with the definition in § 154.20.
(3) Have mechanical, electrical, and utility equipment elevated to or above one foot above the base flood elevation or floodproofed so that below one foot above the base flood elevation they are:
(a) Watertight and substantially impermeable to the passage of water; and,
(b) Capable of resisting hydrostatic and hydrodynamic loads and effects of buoyancy.
(4) A registered professional engineer or architect shall certify that the standards of this section are satisfied. A floodproofing certificate shall be provided to the Floodplain Administrator as set forth in § 154.33.
(5) Have flood openings in compliance with the requirements below: The structure shall be designed to automatically provide for the entry and exit of floodwaters for the purpose of equalizing hydrostatic forces. Designs for meeting this requirement must either be certified by a registered professional engineer or architect or meet or exceed the following minimum criteria:
(a) A minimum of two openings having a net area of not less than one square inch for every one square foot of enclosed space,
(b) The bottom of all openings shall not be higher than one foot above grade, and
(c) Openings may be equipped with screens, louvers, valves, or other coverings or devices provided that they allow the automatic entry and exit of floodwaters.
(6) If the structure is converted to another use, it must be brought into full compliance with the minimum standards governing such use.
(D) Critical facilities. New construction or substantial improvement of any critical facility is prohibited in all areas of the floodplain and the 0.2% annual chance floodplain, unless all of the following provisions are met:
(1) No feasible alternative site exists for the construction of an equivalent facility within the corporate or extraterritorial jurisdiction boundaries of the city;
(2) The facility has the lowest floor, including basement, of all structures elevated to one foot above the 0.2% annual chance flood elevation or, together with attendant utility and sanitary facilities, floodproofed so that below one foot above the 0.2% annual chance flood elevation:
(a) The structure is watertight with walls substantially impermeable to the passage of water; and
(b) The structure has structural components with the capability of resisting hydrostatic and hydrodynamic loads and effects of buoyancy.
(c) A registered professional engineer or architect shall certify that the standards of the subsection are satisfied. Such certification shall be provided to the Floodplain Administrator as set forth in § 154.33.
(3) If the 0.2% annual chance floodplain is not identified, the facility shall have the lowest floor, including basement, elevated to three feet above the base flood elevation or be floodproofed to three feet above the base flood elevation with the standards in § 154.41(C)(1)(b).
(4) The facility has at least one access road connected to land outside the 0.2% annual chance floodplain that is capable of carrying emergency support vehicles and the top of the access road is no lower than the 0.2% annual chance flood elevation.
(E) Space below lowest floor.
(1) Fully enclosed areas below the lowest floor (excluding basements) and below the base flood elevation shall be used solely for the parking of vehicles, building access, or limited storage of readily removable items.
(2) Fully enclosed areas below the lowest floor (excluding basements) and below the base flood elevation shall be designed to automatically equalize hydrostatic flood forces on exterior walls by allowing for the entry and exit of floodwaters. The size of such enclosed areas shall not exceed the maximum clearance height of four feet. Designs for meeting this requirement must either be certified by a registered professional engineer or architect or meet or exceed the following minimum criteria:
(a) A minimum or two openings having a net total area of not less than one square inch for every one square foot of enclosed space,
(b) The bottom of all openings shall not be higher than one foot above grade, and
(c) Openings may be equipped with screens, louvers, valves, or other coverings or devices provided that they allow the automatic entry and exit of floodwaters.
(F) Accessory structures. Structures accessory to a principal building may have the lowest floor below one foot above base flood elevation provided that the structure complies with the following requirements:
(1) The structure shall not be used for human habitation.
(2) The use of the structure must be limited to parking of vehicles or storage of items readily removable in the event of a flood warning.
(3) The floor area shall not exceed 800 square feet.
(4) The structure shall have a low damage potential.
(5) The structure must be adequately anchored to prevent flotation, collapse, or other lateral movement.
(6) The structure shall be designed to automatically provide for the entry and exit of floodwaters for the purpose of equalizing hydrostatic forces. Designs for meeting this requirement must either be certified by a registered professional engineer or architect or meet or exceed the following minimum criteria:
(a) A minimum of two openings having a net area of not less than one square inch for every one square foot of enclosed space,
(b) The bottom of all openings shall not be higher than one foot above grade, and
(c) Openings may be equipped with screens, louvers, valves, or other coverings or devices provided that they allow the automatic entry and exit of floodwaters.
(7) No utilities shall be installed except electrical fixtures in the structure, which must be elevated to or above one foot above the base flood elevation or floodproofed so that below one foot above the base flood elevation they are:
(a) Watertight and substantially impermeable to the passage of water; and,
(b) Capable of resisting hydrostatic and hydrodynamic loads and effects of buoyancy. A registered professional engineer or architect shall certify that the standards of this section are satisfied. A floodproofing certificate shall be provided to the Floodplain Administrator as set forth in § 154.33.
(8) The structure shall be constructed and placed on the building site so as to offer the minimum resistance to the flow of floodwaters.
(9) If the structure is converted to another use, it must be brought into full compliance with the minimum standards governing such use.
(G) Manufactured homes.
(1) Require that all manufactured homes meeting the criteria below to be placed or substantially improved within floodplains on sites be elevated on a permanent foundation such that the lowest floor of the manufactured home is at or above one foot above the base flood elevation and be securely anchored to an adequately anchored foundation system in accordance with the provisions of this section:
(a) Outside of a manufactured home park or subdivision,
(b) In a new manufactured home park or subdivision,
(c) In an expansion to an existing manufactured home park or subdivision, or
(d) In an existing manufactured home park or subdivision on which a manufactured home as incurred substantial damage as the result of a flood.
(2) Require that manufactured homes to be placed or substantially improved on sites in an existing manufactured home park or subdivision within special flood hazard areas that are not subject to the provisions of § 154.41(G)(1) be elevated so that either;
(a) The lowest floor of the manufactured home is at or above one foot above the base flood elevation, or
(b) The manufactured home chassis is supported by reinforced piers or other foundation elements of at least equivalent strength that are no less than 36 inches in height above grade; and be securely anchored to an adequately anchored foundation system in accordance with the provisions of § 154.41(G)(4).
(3) New manufactured home parks of five acres or 50 lots, whichever is less, shall follow the standards of § 154.42(H).
(4) All manufactured homes shall be anchored to resist flotation, collapse, or lateral movement. Manufactured homes must be anchored in accordance with local building codes or FEMA guidelines. In the event that over-the-top ties to ground anchors are used, the following specific requirements (or their equivalent) shall be met:
(a) Over-the-top ties be provided at each of the four corners of the manufactured home, with two additional ties per side at intermediate locations and manufactured homes less than 50 feet long requiring one additional tie per side;
(b) Frame ties be provided at each corner of the manufactured home with five additional ties per side at intermediate points and manufactured homes less than 50 feet long requiring four additional ties per side;
(c) Any additions to the manufactured home be similarly anchored.
(H) Existing structures.
(1) The provisions of this chapter do not require any changes or improvements to be made to lawfully existing structures. However, when an improvement is made to a structure in the floodplain, a floodplain development permit is required and the provisions of § 154.41(G)(2)-(4) shall apply.
(2) Any addition, alteration, reconstruction, or improvement of any kind to an existing structure where the costs of which would equal or exceed 50% of the pre-improvement market value shall constitute a substantial improvement and shall fully comply with the provisions of this chapter.
(3) Any addition, alteration, reconstruction, or improvement of any kind to an existing structure in the floodway shall comply with the provisions of § 154.40(C).
(4) Any addition, alteration, reconstruction, or improvement of any kind to an existing structure that will change the compliance requirements of the building shall require applicable documentation including an elevation certificate, floodproofing certificate, or no rise certification.
(Ord. 734, passed 3-8-2023)