All properties subject to the regulations of this article must comply with the following applicable performance standards:
A. General Construction Requirements: All structures shall be:
1. Adequately anchored to prevent flotation, collapse or lateral movement of the structure; and
2. Constructed with materials and utility equipment resistant to flood damage; and
3. Constructed by methods and practices that minimize flood damage.
B. Class 1 Critical Facilities:
1. Class 1 critical facilities may not be located within a flood hazard area.
2. Class 1 critical facilities must be located with a means of vehicular access that will remain passable during occurrence of the 0.2% flood event.
C. Residential Buildings:
1. All new or substantially improved residential structures must have the lowest floor of the original structure and any lateral addition elevated a minimum of one foot (1') above the flood hazard elevation.
2. Where existing topography, street grades, or other factors preclude elevating by fill, alternate methods of elevating, such as piers, may be allowed, subject to approval by the building official. In such a case, a licensed professional shall certify that the methods used will be adequate to support the structure as well as withstand the various forces and hazards associated with flooding.
D. Nonresidential Buildings:
1. All new or substantially improved nonresidential buildings must have the lowest floor of the original structure and any lateral addition elevated a minimum of one foot (1') above the flood hazard elevation or, together with attendant utility and sanitary systems, be floodproofed to such a level.
2. 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 flood hazard, and that the structure below the flood hazard elevation is watertight with walls substantially impermeable to the passage of water. Such certification must also indicate the specific elevation, in relation to national geodetic vertical datum, to which any structures are floodproofed. A record of this certification will be retained in the office of the building official.
E. All New And Substantially Improved Structures:
1. Fully enclosed areas below the "lowest floor" 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 to meet or exceed the following minimum approval criteria:
a. There must be 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. The openings shall not be located on the same wall.
b. The openings shall be located on exterior walls such that the 1% flood elevation, or shallow flood elevation, is above the bottom of the opening, and in all cases the bottom of all openings shall be no higher than one foot (1') above grade.
c. Openings shall permit the automatic entry and exit of floodwaters.
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 elevated or floodproofed to one foot (1') above the flood hazard elevation.
F. Manufactured Housing: Manufactured housing, including those placed in existing manufactured housing parks, planned developments, or subdivisions, must be:
1. Anchored to resist flotation, collapse or lateral movement.
2. Elevated on a permanent foundation such that the lowest floor of the structure is a minimum of one foot (1') above the flood hazard elevation.
G. Utility And Sanitary Systems:
1. All new or replacement on site sewage waste disposal systems must be located or designed to avoid impairment to the system or contamination from the system during flooding.
2. New or replacement water supply systems and sanitary sewage systems must be designed to minimize or eliminate infiltration of floodwaters into the system. Water supply facilities and sanitary sewage systems must be provided with a level of protection equal to or greater than one foot (1') above the flood hazard elevation.
3. Utilities, such as gas or electrical systems, must be located and constructed to minimize or eliminate flood damage to the system and the risk associated with such flood damage or impaired systems.
H. Storage Of Flammable, Explosive Or Injurious Materials: 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 flood hazard elevation. 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.
I. Flood Control Structural Works: Flood control structural works, including, but not limited to, levees and flood walls, must provide, at a minimum, protection from a 0.2% flood event with a minimum of three feet (3') of design freeboard and must provide for adequate interior drainage. In addition, flood control structural works must be approved by the Iowa department of natural resources or its assignee.
J. Inhibiting Floodways And Drainage Facilities: No use shall affect the capacity or conveyance of the channel or floodway of any tributary to the main stream, drainage ditch or other drainage facility or system.
K. Subdivisions:
1. Subdivisions and planned developments, including manufactured housing parks, must be designed to minimize flood damage and must have adequate drainage provided to reduce exposure to flood damage, and must meet the applicable performance standards established by the city engineer. Development associated with subdivision proposals (including the installation of public utilities) shall meet the applicable performance standards of this article. Any subdivision, planned development, or manufactured housing park intended for residential development must provide all lots with a means of vehicular access that will remain passable during occurrence of the 1% flood event.
2. Proposals for subdivisions shall include the flood hazard elevation data for those areas located within flood hazard areas.
L. Residential Accessory Structures: The exemption of detached garages, sheds and similar structures from the general floodplain management for residential buildings may result in increased premium rates for insurance coverage of the structure and contents; however, said detached garages, sheds and similar accessory type structures are exempt from the general floodplain management for residential buildings when all of the following conditions exist:
1. The structure is not used for human habitation.
2. The structure is designed so as to have low flood damage potential.
3. The structure is constructed and placed on the building site so as to offer minimum resistance to the flow of floodwaters.
4. The structure is firmly anchored to prevent flotation, which may result in damage to other structures.
5. The service facilities for the structure, such as electrical and heating equipment, are elevated or floodproofed to at least one foot (1') above the flood hazard elevation.
6. There shall be 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. The openings shall not be located on the same wall.
7. The openings shall be located on exterior walls such that the 1% flood elevation, or shallow flood elevation, is above the bottom of the opening, and in all cases the bottom of all openings shall be no higher than one foot (1') above grade.
8. Openings shall permit the automatic entry and exit of floodwaters.
M. Recreational Vehicles:
1. Recreational vehicles are exempt from the requirements of subsection F of this section 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 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 F of this section regarding anchoring and elevation of manufactured homes. (Ord. 10-4414, 11-16-2010)