Resolution 2025-075 – Resolution Setting as Public Hearing to Consider Adoption of an Updated Floodplain Management Ordinance for the City of Tiffin, Iowa.

above the base flood elevation, 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 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 1988) to which any structures are floodproofed shall be maintained by the Floodplain Administrator. 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. (ALTERNATIVE LANGUAGE: A minimum of two (2) openings, with positioning on at least two (2) walls, 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.) [Note: The NFIP’s Lowest Floor Guide requires that openings be located on “at least two walls”. While FEMA does not require the ordinance to contain this language, including it might help to ensure that the property owner will receive a lower flood insurance premium.] b. The bottom of all openings shall be no higher than one foot 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. (OPTIONAL LANGUAGE: Where the distance between the floor and ceiling of the fully enclosed area below the “lowest floor” is (FIVE (5) feet or more, the applicant shall be required to sign and record with the Johnson County Recorder a Non-Conversion Agreement that ensures the lower enclosed area remains compliant with the criteria outlined in this subsection.) [Note: Community may determine the height of the lower-enclosed area at which to require the applicant to sign a Non-Conversion Agreement.] (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 box, hot water heater, heating, air conditioning, ventilation equipment (including ductwork), and other similar machinery and equipment elevated (or in the case on non-residential structures, cty_hr_d_160.doc - 10 - 4/15/2021