1048.10  FLOODPLAIN MANAGEMENT.
   The floodplain management criteria shall be as follows:
   (a)   Base Flood Elevation and Location of Floodplain and Floodway.
      (1)   The Base Flood Elevations (BFE) shall be as delineated on the 100-year profile and floodplain maps as noted on the FEMA Flood Insurance Study maps and profiles, or the best available information as determined by the Director.
      (2)   The location of the regulatory floodway and its accompanying flood elevation shall be as delineated on the FEMA regulatory floodway maps.
      (3)   When no base flood or 100-year frequency flood elevation information exists, the base flood or 100-year frequency flood elevation shall be determined by the licensed professional-engineer using an appropriate model or technique as approved by the Director.
      (4)   Nothing contained herein shall prohibit the application of these regulations to land that can be demonstrated by engineering survey to lie within any floodplain. Conversely, any lands (except for those located in a regulatory floodway) that can be demonstrated by a topographic survey certified by a state licensed professional engineer or state licensed professional land surveyor to lie beyond the floodplain, and to the satisfaction of the Director, to have been higher than the base flood elevation as of the effective date of the first regulatory floodplain map denoting the site to be in a floodplain, or for unmapped floodplains as of the effective date of the ordinance, shall not be subject to the regulations of this section.
      (5)   In the case of a site located in the regulatory floodway that is higher than the BFE, it is subject to the regulations of this section until such time as a letter of map revision is received from the FEMA.
   (b)   Performance Standards Applicable to all Floodplain Development.
      (1)   Modification and disturbance of natural riverine floodplains shall be avoided to protect existing hydrologic and environmental functions. Such disturbances shall be minimized and all negative impacts mitigated as described in a mitigation plan.
      (2)   No development shall be allowed in the floodplain that shall singularly or cumulatively create a damaging or potentially damaging increase in flood heights or velocity or threat to public health, safety and welfare or impair the natural hydrologic functions of the floodplain or channel.
      (3)   For all projects involving channel modification, fill, or levees, the flood carrying capacity of the regulatory floodplain shall be maintained.
      (4)   Compensatory storage is required for all lost floodplain storage as follows:
         A.   Hydraulically equivalent compensatory storage requirements for fill or structures in a riverine floodplain shall be at least equal to 1.2 times the volume of floodplain storage lost. Such compensation areas shall be designed to drain freely and openly to the watercourse and located opposite or adjacent to fill areas. The floodplain volume lost below the existing 10-year frequency flood elevation must be replaced below the proposed 10-year frequency flood elevation. The floodplain volume lost above the 10-year existing frequency flood elevation must be replaced above the proposed 10-year frequency elevation.
         B.   Hydraulically equivalent compensatory storage requirements for fill or structures in a nonriverine floodplain shall be at least equal to 1.0 times the volume of floodplain storage lost.
   (c)   Public Health Protection Standards.
      (1)   No developments in the floodplain shall include locating or storing chemicals, explosives, buoyant materials, animal wastes, fertilizers, flammable liquids, pollutants, or other hazardous or toxic materials below the FPE.
      (2)   New and replacement water supply systems, wells, and sanitary sewer lines may be permitted providing all manholes or other above-ground openings located below the Flood Protection Elevation (FPE) are watertight.
   (d)   Building Protection Requirements.
      (1)   All new buildings, building alteration that either increases the first floor area by more than twenty percent or the building's market value by more than fifty percent, the installation of a manufactured home on a new site or a new manufactured home on an existing site or installing a recreational vehicle on a site for more than 180 days and located within a 100-year floodplain shall be protected from flood damage below the flood protection elevation.
      (2)   The lowest floor, including basements for all new construction or substantial improvements of residential structures shall be two feet or more above the base flood elevation.
         A.   If placed on fill, the top of the fill shall be above the flood protection elevation. The fill shall be placed at that elevation for a distance of ten feet out from the building unless the building design is certified by a state licensed structural engineer as protected from damages due to hydrostatic pressures. Additionally, the fill must be demonstrated not to settle below the flood protection elevation and to be adequately protected against erosion, scour and differential settlement.
         B.   If elevated by means of walls, pilings, or other foundation, the building's supporting structure must be permanently open to flood waters and not subject to damage by hydrostatic pressures of the base flood or 100-year frequency flood. The permanent openings shall be no more than one foot above grade, and consist of a minimum of two openings. The openings must have a total net area of not less than one square inch for every one square foot of enclosed area subject to flooding below the BFE. The foundation and supporting members shall be anchored and aligned in relation to flood flows and adjoining structures so as to minimize exposure to known hydrodynamic forces such as current, waves, ice and floating debris. All areas below the Flood Protection Elevation shall be constructed of materials resistant to flood damage. The lowest floor (including basement) and all electrical, heating, ventilating, plumbing, and air conditioning equipment and utility meters shall be located at or above the FPE. Water and sewer pipes, electrical and telephone lines, submersible pumps and other waterproofed service facilities may be located below the flood protection elevation. No area below the flood protection elevation shall be used for storage of items or materials.
      (3)   The lowest floor including basement of all new construction or substantial improvements of nonresidential buildings shall be two feet or more above the base flood elevations in accordance with paragraph (2) above or be structurally dry flood proofed. A nonresidential building may be structurally dry flood proofed (in lieu of elevation) provided that a state licensed professional engineer or structural engineer shall certify that the building has been structurally dry flood proofed below the flood protection elevation and the structure and attendant utility facilities are watertight and capable of resisting the effects of the base flood or 100-year frequency flood. The building design shall take into account flood velocities, duration, rate of rise, hydrostatic and hydrodynamic forces, the effects of buoyancy and impacts from debris or ice. Flood proofing measures shall be operable without human intervention and without an outside source of electricity. (Levees, berms, floodwalls and similar works are not considered flood proofing for the purpose of this subsection.)
      (4)   Manufactured homes and recreational vehicles to be installed on a site for more than 180 days, shall be elevated to or above the flood protection elevation and shall be anchored to resist flotation, collapse, or lateral movement by being tied down in accordance with applicable rules and regulations.
      (5)   Tool sheds and detached garages on an existing single-family platted lot, may be constructed with the lowest floor below the flood protection elevation in accordance with the following:
         A.   The building is not used for human habitation.
         B.   All areas below the base flood or 100-year frequency flood elevation shall be constructed with waterproof material. Structures located in a regulatory floodway shall be constructed and placed on a building site so as not to block the flow of floodwaters.
         C.   The structure shall be anchored to prevent flotation.
         D.   Service facilities such as electrical and heating equipment shall be elevated or flood proofed to the flood protection elevation.
         E.   The building shall be valued at less than five thousand dollars ($5,000.00) and be less than 500 square feet in floor size.
         F.   The building shall be used only for the storage of vehicles or tools and may not contain other rooms, workshops, greenhouses or similar uses.
      (6)   A non-conforming structure damaged by flood, fire, wind or other natural or man-made disaster may be restored unless the damage exceeds fifty percent of its market value before it was damaged, in which case it shall conform to this chapter.
   (e)   If the proposed development would result in a change in the mapped regulatory floodplain or 100-year frequency flood elevation on a site, the applicant shall submit sufficient data to obtain a Letter of Map Revision (LOMR) from FEMA.
   (f)   Any work involving construction or modification or removal of a dam or an on-stream structure to impound water shall obtain a State Dam Safety Permit or letter indicating a permit is not required prior to the start of construction of a dam.
(Ord. 11-01. Passed 8-21-01; Ord. 16-2019.  Passed 12-17-19.)