The regulations set forth in this section or elsewhere in this ordinance which are applicable, shall apply in the FF Floodway Fringe Overlay Zoning District.
1. Principal Permitted Uses. All uses within the Floodway Fringe Overlay Zoning District shall be limited to the extent that they are not prohibited by the underlying zoning district or any other section of this ordinance and provided they meet applicable performance standards of the Floodway Fringe Overlay Zoning District.
2. Performance Standards. All uses must be consistent with the need to minimize flood damage and shall meet the following applicable performance standards.
A. No development within the Floodway Fringe Overlay Zoning District shall increase the flood heights or flood profile.
B. All structures shall: (i) be adequately anchored to prevent flotation, collapse, or lateral movement of the structure; (ii) be constructed with materials and utility equipment resistant to flood damage; and (iii) be constructed by methods and practices that minimize flood damage.
C. Nonresidential Buildings. All new or substantially improved non-residential buildings shall have the first floor (including basement) elevated a minimum of one (1) foot above the one hundred (100) year flood level, or together with attendant utility and sanitary systems, be flood proofed to such a level. When floodproofing is utilized, a professional engineer registered in the State of Iowa shall certify that the floodproofing methods used are adequate to withstand the flood depths, pressures, velocities, impact and uplift forces, and other factors associated with the one hundred (100) year flood level; and that the structure, below the one hundred (100) year flood level, is watertight with walls substantially impermeable to the passage of water. A record of the certification indicating the specific elevation (North American Vertical Datum) to which any structures are flood proofed shall be maintained by the Zoning Administrator.
D. Residential Buildings. All new or substantially improved residential structures shall have the lowest floor (including basement) elevated a minimum of one (1) foot above the one hundred (100) year flood level. Construction shall be upon compacted fill which shall, at all points, be no lower than one (1) foot above the one hundred (100) year flood level. Alternate methods of elevating (such as piers) may be allowed subject to favorable consideration of the Norwalk Board of Adjustment and issuance of a variance by the Board of Adjustment, where existing topography, street grades, or other factors preclude elevating by fill. In such cases, the methods used must be adequate to support the structure as well as withstand the various forces and hazards associated with flooding, and be engineered by a registered professional engineer in the State of Iowa.
E. All New and Substantially Improved Structures. Fully enclosed areas below the lowest floor (not including basement) that are subject to flooding shall be designed to automatically equalize hydrostatic flood forces on exterior walls by allowing for the entry and exit of floodwater. Designs for meeting this requirement must be certified by a registered professional engineer or meet or exceed the following minimum criteria:
(1) A minimum of two openings having a total net area of not less than one (1) 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 (1) foot above grade.
(3) Openings may be equipped with screens, louvers, valves, or other coverings or devices provided they permit the automatic entry and exit of floodwaters.
(4) All such areas shall be used solely for parking of vehicles, building access, and low damage potential storage.
(Ord. 18-20 – May 19 Supp.)
F. New and substantially improved structures must be designed (or modified) and adequately anchored to prevent flotation, collapse, or lateral movement of the structure resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy.
G. New and substantially improved structures must be constructed with electrical, heating, ventilation, plumbing, and air conditioning equipment and other service facilities that are designed and/or located so as to prevent water from entering or accumulating within the components during conditions of flooding.
H. Utility Systems.
(1) All new and replacement sanitary sewage systems shall be designed to minimize or eliminate infiltration of flood waters into the system as well as the discharge of effluent into flood waters. Wastewater treatment facilities shall be provided with a level of flood protection equal to or greater than one (1) foot above the one hundred (100) year flood elevation.
(2) On site waste disposal systems shall be located or designed to avoid impairment to the system or contamination from the system during flooding.
(3) New or replacement water supply systems shall be designed to eliminate infiltration of flood waters into the system. Water supply treatment facilities shall be provided with a level of protection equal to or greater than one (1) foot above the one hundred (100) year flood elevation.
(4) Utilities such as gas and electrical systems shall be located and constructed to minimize or eliminate flood damage to the system and the risk associated with flood damaged or impaired system.
I. Storage of materials and equipment that are flammable, explosive, hazardous, or injurious to human, animal, or plant life is prohibited unless elevated a minimum of one (1) foot above the one hundred (100) year flood level. Other material and equipment must either be similarly elevated or: (i) not be subject to major flood damage and be anchored to prevent movement due to flood waters; or (ii) be readily removable from the area within the time available after flood warning.
J. Flood control structural works such as levees, flood walls, etc. shall provide, at a minimum, a protection from a one hundred (100) year flood with a minimum of three (3) foot of design freeboard and shall provide for adequate interior drainage. In addition, structural flood control works shall be approved by the Iowa Department of Natural Resources.
K. No use shall affect the capacity or conveyance of the channel or floodway or any tributary to the main stream, drainage ditch, or other drainage facility or system.
L. Accessory Structures to Residential Uses. Detached garages, sheds, and similar structures that are incidental to a residential use are exempt from the base flood elevation requirements where the following criteria are satisfied.
(1) The structure shall be designed to have low flood damage potential. Its size shall not exceed 600 square feet in size. Those portions of the structure located less than one foot above the BFE must be constructed of flood-resistant materials.
(2) The structure shall be used solely for low flood damage potential purposes such as vehicle parking and limited storage. The structure shall not be used for human habitation.
(3) The structure shall be constructed and placed on the building site so as to offer minimum resistance to the flow of floodwaters.
(4) The structure shall be firmly anchored to resist flotation, collapse and lateral movement.
(5) The structure’s service facilities such as electrical and heating equipment shall be elevated or floodproofed to at least one foot above the base flood elevation.
(6) The structure’s walls shall include openings that satisfy the provisions of Paragraph 2(E) of this section.
(7) Exemption from the 100-year flood elevation requirements for such a structure may result in increased premium rates for flood insurance coverage of the structure and its contents.
(Ord. 18-20 – May 19 Supp.)
M. Factory-Built Homes.
(1) All factory-built homes, including those placed in existing factory-built home parks or subdivisions, shall be elevated on a permanent foundation such that the lowest floor of the structure is a minimum of one (1) foot above the 100-year flood level.
(2) All factory-built homes, including those placed in existing factory-built home parks or subdivisions, shall be anchored to resist flotation, collapse, or lateral movement. Methods of anchoring may include, but are not limited to, use of over-the-top or frame ties to ground anchors as required by the State Building Code.
(Ord. 18-20 – May 19 Supp.)
N. Subdivisions (including factory-built home parks and subdivisions) shall be consistent with the need to minimize flood damages and shall have adequate drainage provided to reduce exposure to flood damage. Development associated with subdivision proposals shall meet the applicable performance standards. Subdivision proposals intended for residential development shall provide all lots with a means of vehicular access that will remain above flood levels during occurrence of the one hundred (100) year flood. Proposals for subdivisions greater than five (5) acres or fifty (50) lots (whichever) is less shall include 100-year flood elevation data for those areas located within the Floodway Fringe Overlay District.
O. Recreational vehicles are exempt from the requirements of Paragraph M of this subsection regarding anchoring and elevation of factory-built homes when the following criteria are satisfied:
(1) The recreational vehicle shall be located on the site for less than 180 consecutive days; and
(2) The recreational vehicle must be fully licensed and ready for highway use. A recreational vehicle is ready for highway use if it is on its wheels or jacking system and is attached to the site only by quick disconnect type utilities and security devices and has no permanently attached additions.
Recreational vehicles that are located on the site for more than 180 consecutive days or are not ready for highway use must satisfy requirements of Paragraph M of this section regarding anchoring and elevation of factory-built homes.