All uses must be consistent with the need to minimize flood damage and meet the following applicable performance standards. Where 100-year flood data has not been provided in the flood insurance study, the Iowa department of natural resources shall be contacted to determine: a) whether the land involved is either wholly or partly within the floodway or floodway fringe and b) the 100-year flood level. The applicant will be responsible for providing the department of natural resources with sufficient technical information to make such determination.
A. All Development: All development within the areas of significant flood hazard shall:
1. Be consistent with the need to minimize flood damage.
2. Use construction methods and practices that will minimize flood damage.
3. Use construction materials and utility equipment that are resistant to flood damage.
4. Obtain all other necessary permits from federal, state and local governmental agencies including approval when required from the Iowa department of natural resources.
B. Residential Buildings:
1. All new or substantially improved residential structures shall have the lowest floor, including basement, elevated a minimum of one foot (1') above the 100-year flood level. Construction shall be upon compacted fill which shall, at all points, be no lower than one foot (1') above the 100-year flood level and extend at such elevation at least eighteen feet (18') 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 council, 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.
2. All new residential structures shall be provided with a means of access which will be passable by wheeled vehicles during the 100-year flood.
C. Nonresidential Buildings: All new or substantially improved nonresidential buildings shall have the lowest floor (including basement) elevated a minimum of one foot (1') above the 100-year flood level, 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 100-year flood; and that the structure, below the 100-year flood level is watertight with walls substantially impermeable to the passage of water. A record of the certification indicating the specific elevation (in relation to national geodetic vertical datum) to which any structures are floodproofed shall be maintained by the administrator.
D. New And Substantially Improved Structures: The following shall be required for 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 (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.
b. The bottom of all openings shall be no higher than one foot (1') above grade.
c. Openings may be equipped with screens, louvers, valves, or other coverings or devices, provided they permit the automatic entry and exit of floodwaters.
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 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.
E. 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 foot (1') 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.
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 floodwaters into the system as well as the discharge of effluent into floodwaters. Wastewater treatment facilities (other than on site systems) shall be provided with a level of flood protection equal to or greater than one foot (1') above the 100-year flood elevation.
3. New or replacement water supply systems shall be designed to minimize or eliminate infiltration of floodwaters 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 (1') above the 100-year 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 such flood damaged or impaired systems.
G. Storage Of Materials And Equipment: 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 (1') above the 100-year flood level. Other material and equipment must either be similarly elevated or: 1) not be subject to major flood damage and be anchored to prevent movement due to floodwaters or 2) 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, floodwalls, etc., shall provide, at a minimum, protection from a 100-year flood with a minimum of three feet (3') 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 carrying capacity within the altered or relocated portion. In addition, such alterations or relocations must be approved by the department of natural resources.
J. Subdivisions And Factory Built Home Parks And 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 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 area of significant flood hazard.
K. Accessory Structures:
1. Detached garages, sheds, and similar structures accessory to a residential use are exempt from the 100-year flood elevation requirements where the following criteria are satisfied:
a. The structure shall not be used for human habitation.
b. The structure shall be designed to have low flood damage potential.
c. The structure shall be constructed and placed on the building site so as to offer minimum resistance to the flow of floodwaters.
d. The structure shall be firmly anchored to prevent flotation which may result in damage to other structures.
e. The structure's service facilities such as electrical and heating equipment shall be elevated or floodproofed to at least one foot (1') above the 100-year flood level.
2. 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.
L. Recreational Vehicles:
1. Recreational vehicles are exempt from the requirements of subsection E of this section regarding anchoring and elevation of factory built homes when the following criteria are satisfied:
a. The recreational vehicle shall be located on the site for less than one hundred eighty (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 one hundred eighty (180) consecutive days or are not ready for highway use must satisfy requirements of subsection E of this section 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. (Ord. 2002-104, 8-27-2002)
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