In all areas of special flood hazard where base flood elevation data has been provided, as set forth in Section 4.08.040 or Section 4.08.150(j), the following provisions are required:
(a) Residential Construction. New construction or substantial improvement of any residential structure (including manufactured homes) shall have the lowest floor elevated no lower than two feet above the base flood elevation. No basements are permitted. Should solid foundation perimeter walls be used to elevate a structure, openings sufficient to facilitate the unimpeded movements of floodwaters shall be provided in accordance with subsection (e) of this section.
(b) Nonresidential Construction. New construction or substantial improvement of any commercial, industrial, or nonresidential structure (including manufactured homes) shall have the lowest floor elevated no lower than two feet above the level of the base flood elevation. Should solid foundation perimeter walls be used to elevate a structure, openings sufficient to facilitate the unimpeded movements of floodwaters shall be provided in accordance with subsection (e) of this section. No basements are permitted. Structures located in A-zones may be floodproofed in lieu of elevation provided that all areas of the structure below the required elevation are watertight with walls substantially impermeable to the passage of water, using structural components having the capability of resisting hydrostatic and hydrodynamic loads and the effect of buoyancy. A registered, professional engineer or architect shall certify that the standards of this subsection are satisfied. Such certifications shall be provided to the official as set forth in Sections 4.08.140(g) and 4.08.140(i). A variance may be considered for wet-floodproofing agricultural structures in accordance with the criteria outlined in Section 4.08.220 of this chapter. Agricultural structures not meeting the criteria of Section 4.08.220 must meet the nonresidential construction standards and all other applicable provisions of this chapter. Structures that are floodproofed are required to have an approved maintenance plan with an annual exercise. The local administrator must approve the maintenance plan and notification of the annual exercise shall be provided to same.
(c) Manufactured Homes.
(1) Manufactured homes that are placed or substantially improved on sites outside a manufactured home park or subdivision, in a new manufactured home park or subdivision, in an expansion to an existing manufactured home park or subdivision, or in an existing manufactured home park or subdivision on which a manufactured home has incurred “substantial damage” as the result of a flood, must be elevated on a permanent foundation such that the lowest floor of the manufactured home is elevated no lower than two feet above the base flood elevation and be securely anchored to an adequately anchored foundation system to resist flotation, collapse and lateral movement.
(2) Manufactured homes that are to be placed or substantially improved on sites in an existing manufactured home park or subdivision that are not subject to the provisions of subsection (c)(1) of this section must be elevated so that the lowest floor of the manufactured home is elevated no lower than two feet above the base flood elevation, and be securely anchored to an adequately anchored foundation to resist flotation, collapse and lateral movement.
(3) Manufactured homes shall be anchored to prevent flotation, collapse, or lateral movement. For the purpose of this requirement, manufactured homes must be anchored to resist flotation, collapse, or lateral movement in accordance with Section 19-425.39 of the South Carolina Manufactured Housing Board Regulations, effective date May 25, 1990, as amended. Additionally, when the elevation requirement would be met by an elevation of the chassis at least thirty-six inches or less above the grade at the sight, reinforced piers or other foundation elements of at least equivalent strength shall support the chassis. When the elevation of the chassis is above thirty-six inches in height an engineering certification is required.
(4) An evacuation plan must be developed for evacuation of all residents of all new, substantially improved or substantially damaged manufactured home parks or subdivisions located within flood-prone areas. This plan shall be filed with and approved by the local administrator and the local emergency preparedness coordinator.
(d) Recreational Vehicles. A recreational vehicle is ready for highway use if it is on wheels or jacking system, is attached to the site only by quick-disconnect type utilities and security devices, and has no permanently attached additions. Recreational vehicles placed on sites shall either be on site for fewer than one hundred eighty consecutive days and be fully licensed and ready for highway use, or meet the requirements of Section 4.08.140 and Section 4.08.170 and subsection (c) of this section.
(e) Elevated Buildings. New construction or substantial improvements of elevated buildings that include fully enclosed areas that are usable solely for the parking of vehicles, building access, or storage in an area other than a basement, and which are subject to flooding shall be designed to preclude finished space and be designed to automatically equalize hydrostatic flood forces on exterior walls by allowing for the entry and exit of floodwaters.
(1) Designs for complying with this requirement must either be certified by a professional engineer or architect or meet the following minimum criteria:
(A) Provide a minimum of two openings on different walls having a total net area of not less than one square inch for every square foot of enclosed area subject to flooding;
(B) The bottom of all openings shall be no higher than one foot above grade;
(C) Openings may be equipped with screens, louvers, valves, or other coverings or devices provided they permit the automatic flow of floodwaters in both directions; and
(D) Fill placed around foundation walls must be graded so that the grade inside the enclosed area is equal to or higher than the adjacent grade outside the building on at least one side of the building.
(2) Hazardous Velocities. Hydrodynamic pressure must be considered in the design of any foundation system where velocity waters or the potential for debris flow exists. If flood velocities are excessive (greater than five feet per second), foundation systems other than solid foundation walls should be considered so that obstructions to damaging flood flows are minimized.
(3) Access to the enclosed area shall be the minimum necessary to allow for parking of vehicles (garage door) or limited storage of maintenance equipment used in connection with the premises (standard exterior door) or entry to the living area (stairway or elevator).
(4) The interior portion of such enclosed area shall not be partitioned or finished into separate rooms, except to enclose a single storage area and must be void of utilities except for essential lighting as required, and cannot be temperature controlled. One wet location switch and/or outlet connected to a ground fault interrupt breaker may be installed below the required lowest floor elevation specified in subsections (a) through (c) of this section.
(5) All construction materials below the required lowest floor elevation specified in subsections (a) through (c) of this section should be of flood-resistant materials.
(f) Temporary Development. Certain types of structures (e.g., fruit stands, construction site offices, portable toilets, etc.) may be situated temporarily on flood-prone property without having to comply with the elevation or floodproofing criteria of subsections (a) and (b) of this section, respectively, provided that the following criteria are met:
(1) All applicants must submit to the local administrator, prior to the issuance of the development permit, a written plan for the removal of any temporary structures or development in the event of a hurricane or flashflood warning notification. The plan shall be reviewed and approved in writing, and must include the following information:
(A) A specified time period for which the temporary use will be permitted,
(B) The name, address and phone number of the individual responsible for the removal of temporary structures or development,
(C) The time frame prior to the event at which any structures will be removed (i.e., minimum of seventy-two hours before landfall of a hurricane or immediately upon flood warning notification),
(D) A copy of the contract or other suitable instrument with a trucking company to insure the availability of removal equipment when needed,
(E) Designation, accompanied by documentation, of a location outside the floodplain to which any temporary structure will be moved,
(F) A determination of permanent structures which would be adversely affected by increased flooding upstream or downstream, and a method for covering this liability, such as a performance bond, and
(G) A plan to restore the area to its natural condition once the temporary permit expires or the temporary use is terminated, whichever is first;
(2) The structure is mobile, or can be made so, and is capable of being removed from the site with a maximum of four hours warning;
(3) The structure will not remain on the property for more than one hundred eighty days.
(g) Accessory Structures. An accessory structure or garage, the cost of which is greater than three thousand dollars, must comply with the elevated structure requirements of subsections (b) and (e) of this section. When accessory structures of three thousand dollars or less are to be placed in the floodplain, the following criteria shall be met:
(1) Accessory structures shall not be used for human habitation (including work, sleeping, living, cooking or restroom areas);
(2) Accessory structures shall be designed to have low-flood damage potential;
(3) Accessory structures shall be constructed and placed on the building site so as to offer the minimum resistance to the flow of floodwaters;
(4) Accessory structures shall be firmly anchored to prevent flotation, collapse, or lateral movement of the structure;
(5) Service facilities such as electrical and heating equipment shall be installed in accordance with Section 400.4; and
(6) Openings to relieve hydrostatic pressure during a flood shall be provided below base flood elevation in conformance with subsection (e) of this section.
(h) Floodways. Located within areas of special flood hazard established in Section 4.08.040, are areas designated as floodways. The floodway is an extremely hazardous area due to the velocity of floodwaters that carry debris and potential projectiles and has erosion potential. The following provisions shall apply within such areas:
(1) No encroachments, including fill, new construction, substantial improvements, additions, and other developments shall be permitted unless it has been demonstrated through hydrologic and hydraulic analyses performed in accordance with standard engineering practice that the proposed encroachment would not result in any increase in the flood levels during the occurrence of the base flood. Such certification and technical data shall be presented to the local administrator;
(2) If subsection (h)(1) of this section is satisfied, all new construction and substantial improvements shall comply with all applicable flood hazard reduction provisions of Article IV of this chapter;
(3) Stream crossings for any purpose (i.e., timber harvesting operations), if temporary, shall be permitted in accordance with subsection (f) of this section. Otherwise, the development shall comply with all applicable flood hazard reduction provisions of Article IV of this chapter;
(4) No manufactured homes shall be permitted, except in an existing manufactured home park or subdivision. A replacement manufactured home may be placed on a lot in an existing manufactured home park or subdivision provided the anchoring and the elevation standards of subsection (c) of this section are met;
(5) Permissible uses within floodways may include: general farming, pasture, outdoor plant nurseries, horticulture, forestry, wildlife sanctuary, game farm, and other similar agricultural, wildlife and related uses. Also, lawns, gardens, play areas, picnic grounds, and hiking and horseback riding trails are acceptable uses, provided that they do not employ structures or fill. Substantial development of a permissible use may require a no-rise certification. The uses listed in this subsection are permissible only if and to the extent that they do not cause any increase in base flood elevations.
(i) Fill. Fill is discouraged because storage capacity is removed from floodplains. Elevating buildings by other methods must be considered. An applicant shall demonstrate that fill is the only alternative to raising the building to at least two feet above the base flood elevation, and that the amount of fill used will not affect the flood storage capacity or adversely affect adjacent properties. The following provisions shall apply to all fill placed in the special flood hazard area:
(1) Fill may not be placed in the floodway unless it is in accordance with subsection (h)(1) of this section;
(2) Fill may not be placed in tidal or nontidal wetlands without the required state and federal permits;
(3) Fill must consist of soil and rock materials only. A registered professional geotechnical engineer may use dredged material as fill only upon certification of suitability. Landfills, rubble fills, dumps, and sanitary fills are not permitted in the floodplain;
(4) Fill used to support structures must comply with ASTM Standard D-698, and its suitability to support structures certified by a registered, professional engineer;
(5) Fill slopes shall be no greater than two horizontal to one vertical. Flatter slopes may be required where velocities may result in erosion; and
(6) The use of fill shall not increase flooding or cause drainage problems on neighboring properties. (Ord. O-13-06 (part), 2006)