Ordinance No. 2025-521 – An Ordinance to Amend the Municipal Code of Tiffin, Iowa, Chapter 160, Flood Plain Management

N. Maximum Damage Potential Development. All new or substantially improved maximum damage potential development 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 two-tenths percent annual chance flood; and that the structure, below the two-tenths percent 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 two-tenths percent 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. 2. Special Floodway Provisions. In addition to the General Floodplain Standards, development within the floodway must meet the following applicable standards. The floodway is that portion of the floodplain which must be protected from developmental encroachment to allow the free flow of flood waters. Where floodway data has been provided in the Flood Insurance Study, such data shall be used to define the floodway. Where no floodway data has been provided, the Department of Natural Resources shall be contacted to provide a floodway delineation. The applicant will be responsible for providing the Department of Natural Resources with sufficient technical information to make such determination. A. No development shall be permitted in the floodway that would result in any increase in the base flood elevation. Consideration of the effects of any development on flood levels shall be based upon the assumption that an equal degree of development would be allowed for similarly situated lands. B. All development within the floodway 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. C. No development shall affect the capacity or conveyance of the channel or floodway of any tributary to the main stream, drainage ditch or any other drainage facility or system. D. Structures, buildings, recreational vehicles, and sanitary and utility systems, if permitted, shall meet the applicable General Floodplain standards and shall be constructed or aligned to present the minimum possible resistance to flood flows. E. Structures, if permitted, shall have a low flood damage potential and shall not be for human habitation. F. Storage of materials or equipment that are buoyant, flammable, explosive or injurious to human, animal or plant life is prohibited. Storage of other material may be allowed if readily removable from the floodway within the time available after flood warning. G. Watercourse alterations or relocations (channel changes and modifications) 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.