All development within the Floodway Fringe District shall be permitted to the extent that they are not prohibited by any other ordinance or underlying zoning district regulations and provided they meet applicable performance standards of the Floodway Fringe District. All development must be consistent with the need to minimize flood damage and shall meet the following applicable performance standards. Until a regulatory floodway is designated, no development may increase the Base Flood Elevation more than one foot.
(A) Generally. All development shall:
(1) Be designed and adequately anchored to prevent flotation, collapse or lateral movement of the structure;
(2) Use construction materials and utility equipment that are resistant to flood damage; and
(3) Use construction methods and practices that will minimize flood damage.
(B) Residential structures. All new or substantially improved residential structures shall have the lowest floor, including basement, elevated a minimum of one foot above the base flood elevation. Construction shall be upon compacted fill which shall, at all points, be no lower than one foot above the base flood elevation and extend at an elevation at least 18 feet beyond the limits of any structure erected thereon. Alternate methods of elevating (such as piers) may be allowed, subject to favorable consideration by the City Engineering Department, where existing topography, street grades or other factors preclude elevating by fill. In these cases, the methods used must be adequate to support the structure as well as withstand the various forces and hazards associated with flooding. All new residential structures shall be provided with a means of access which will be passable by wheeled vehicles during the base flood.
(C) Nonresidential structures. All new or substantially improved nonresidential structures shall have the lowest floor (including basement) elevated a minimum of one foot above the base flood elevation, or together with attendant utility and sanitary systems, be floodproofed to the same level. When floodproofing is utilized, a professional engineer registered in the state 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 base flood; and that the structure, below the base flood elevation, is watertight with walls substantially impermeable to the passage of water. A record of the certification indicating the specific elevation (in relation to North American Vertical Datum (NAVD) of 1988) to which any structures are floodproofed shall be maintained by the Building and Neighborhood Services Director or his or her designee.
(D) All new and substantially improved structures.
(1) Fully enclosed areas below the lowest floor (not including basements) 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 floodwaters. Designs for meeting this requirement must either be certified by a registered professional engineer or meet or exceed the following minimum criteria:
(a) 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;
(b) The bottom of all openings shall be no higher than one foot above grade; and
(c) Openings may be equipped with screens, louvers, valves or other coverings or devices provided that they permit the automatic entry and exit of floodwaters. The areas shall be used solely for parking of vehicles, building access and low damage potential storage.
(d) All such areas shall be used solely for parking of vehicles, building access and low damage potential storage.
(2) 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.
(3) New and substantially improved structures shall be constructed with electric meter, electrical service panel, water heater, heating, ventilation equipment (including ductwork), and air conditioning equipment and other service equipment and machinery elevated (or in the case of non-residential structures, optionally flood-proofed to) a minimum of one foot above the base flood elevation.
(4) New and substantially improved structures shall be constructed with plumbing, gas lines, water/gas meters and other similar service utilities either elevated (or in the case of non-residential structures, optionally floodproofed to) a minimum of one foot above the base flood elevation or designed to be water tight and withstand inundation to such a level.
(E) Manufactured homes.
(1) All new and substantially improved manufactured homes including those placed in existing manufactured home parks or subdivisions shall be elevated on a permanent foundation so that the lowest floor of the structure is a minimum of one foot above the base flood elevation.
(2) All new and substantially improved manufactured homes including those placed in existing manufactured 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. This requirement is in addition to applicable state and local anchoring requirements for resisting wind forces.
(3) The manufactured home chassis is supported by reinforced piers or other foundation elements of at least equivalent strength that are not less than 36 inches in height above grade.
(F) Utility and sanitary systems.
(1) On-site waste disposal and water supply systems shall be located or designed to avoid impairment to the system or contamination from the system during flooding.
(2) 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 (other than on-site systems) shall be provided with a level of flood protection equal to or greater than one foot above the base flood elevation.
(3) New or replacement water supply systems shall be designed to minimize or eliminate infiltration of flood waters into the system. Water supply treatment facilities other than on-site systems shall be provided with a level of protection equal to or greater than one foot above the base flood elevation.
(4) Utilities such as gas or 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 systems.
(G) Storage of materials and equipment that are flammable.
(1) Storage of materials and equipment that are flammable, explosive or injurious to human, animal or plant life is prohibited unless elevated a minimum of one foot above the base flood elevation.
(2) Other material and equipment must either be similarly elevated or:
(a) Not be subject to major flood damage and be anchored to prevent movement due to flood waters; or
(b) Be readily removable from the area within the time available after flood warning.
(H) Flood control structural works. Flood control structural works such as levees, flood-walls and the like, shall provide, at a minimum, protection from a base flood with a minimum of three feet of design freeboard and shall provide for adequate interior drainage. In addition, structural flood control works shall be approved by the Department of Natural Resources.
(I) Watercourse alterations or relocations. Watercourse alterations or relocations must be designed to maintain the flood within the altered or relocated portion. In addition, the Department of Natural Resources must approve such alterations or relocations.
(J) Subdivisions. 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 (including the installation of public utilities) shall meet the applicable performance standards of this chapter. Subdivision proposals intended for residential use shall provide all lots with a means of access which will be passable by wheeled vehicles during the base flood. Proposals for subdivisions greater than five acres or 50 lots (whichever is less) shall include base flood elevation data for those areas located within the Floodway Fringe District.
(K) Accessory structures to residential uses.
(1) 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:
(a) The structure shall not be used for human habitation;
(b) The structure shall be firmly anchored to prevent flotation, collapse and lateral movement which may result in damage to other structures;
(c) The structure’s service facilities such as electrical and heating equipment shall be elevated or flood-proofed to at least one foot above the base flood elevation;
(d) 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;
(e) The structure shall be used solely for low flood damage potential purposes such as vehicle parking and limited storage; and
(f) The structure shall be constructed and placed on the building site so as to offer minimum resistance to the flow of floodwaters.
(2) Exemption from the base flood elevation requirements for a structure may result in increased premium rates for flood insurance coverage of the structure and its contents.
(3) The structure 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 meet or exceed the following criteria: 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. The bottom of all openings shall be no higher than one foot above grade. Openings may be equipped with screens, louvers, valves, or other coverings or devices provided that they permit the automatic entry and exit of floodwaters.
(L) Recreational vehicles.
(1) Recreational vehicles are exempt from the requirements of division (E) above regarding anchoring and elevation of manufactured homes when the following criteria are satisfied:
(a) The recreational vehicle shall be located on the site for less than 180 consecutive days; and
(b) 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.
(2) Recreational vehicles that are located on the site for more than 180 consecutive days and are not ready for highway use must satisfy requirements of division (E) above regarding anchoring and elevation of factory-built homes.
(M) Pipeline river and stream crossings. Pipeline river and stream crossings shall be buried in the stream bed and banks or otherwise sufficiently protected to prevent rupture due to channel degradation and meandering.
(N) Maximum damage potential development. All new or substantially improved maximum damage potential uses shall have the lowest floor (including basement) elevated a minimum of one foot above the elevation of the 500-year flood, or together with attendant utility and sanitary systems, be floodproofed 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 0.2% annual chance flood; and that the structure, below the 0.2% annual chance flood elevation is watertight with walls substantially impermeable to the passage of water. A record of the certification indicating the specific elevation (in relation to North American Vertical Datum 1988) to which any structures are floodproofed shall be maintained by the Administrator. Where 0.2% chance flood elevation data has not been provided in the Flood Insurance Study, the Iowa Department of Natural Resources shall be contacted to compute such data. The applicant will be responsible for providing the Department of Natural Resources with sufficient technical information to make such determinations.
(O) Fill within the floodway fringe shall result in no net loss of natural floodplain storage. The volume of the loss of floodwater storage due to filling in the floodway fringe shall be offset by providing an equal volume of flood storage by excavation or other compensatory measures at or adjacent to the development site. If this is technically infeasible due to lot size, the developer must make every effort to reduce the effects of fill within the floodplain by providing the most compensatory storage possible on the lot.
(1999 Code, § 160.11) (Ord. 2442, passed 4-26-2011; Ord. 2539, passed 7-12-2016; Ord. 2556, passed 10-24-2017; Ord. 2638, passed 4-28-2020; Ord. 2649, passed 7-14-2020; Ord. 2721, passed 2-28- 2023) Penalty, see §
10.99