(A) The only development in a regulatory floodway which will be allowed are appropriate uses which will not cause an increase in flood heights or velocities for all flood events up to and including the base flood. Only those appropriate uses listed below will be allowed in the regulatory floodway.
(B) Appropriate uses do not include the construction or placement of any new structures, fill, building additions, buildings on stilts, fencing (including landscaping or planting designed to act as a fence) and storage of materials except as specifically defined below as an appropriate use. If the development is proposed for the regulatory floodway portion of the regulatory floodplain, the following standards apply in addition to the standards for the regulatory floodplain.
(1) Only the construction, modification, repair or replacement of the following appropriate uses will be allowed in the regulatory floodway;
(a) Public flood control structures and private improvements relating to the control of drainage and flooding of existing buildings, erosion, water quality or habitat for fish and wildlife;
(b) Structures or facilities relating to functionally water dependent uses such as additions, modifications and improvements to existing wastewater treatment plants (except for additions to habitable structures on the site) and facilities and improvements relating to recreational boating (this does not include new wastewater treatment plants);
(c) Storm and sanitary sewer outfalls;
(d) Underground and overhead utilities;
(e) Recreational facilities such as playing fields, open pavilions and trail systems including any related fencing (at least 50% open when viewed from any one direction) built parallel to the direction of flood flows;
(f) Detached garages, storage sheds, boat houses or other non-habitable structures without sanitary facilities that are accessory to existing buildings and will not block flood flows nor reduce regulatory floodway storage;
(g) Bridges, culverts and associated roadways, sidewalks and railways, required for crossing the regulatory floodway or for access to other appropriate uses in the regulatory floodway and any modification thereto;
(h) Parking lots built at or below existing grade provided that either:
1. The BFE is less than one foot above the proposed parking lot; or
2. The parking lot is accessory to short-term outdoor recreational facilities and the owner agrees to restrict access during periods of inundation and agrees to accept liability for all damage caused by vehicular access during flooding events.
(i) Regulatory floodway grading, without fill, to create a positive non-erosive slope
toward a channel;
(j) Floodproofing activities to protect previously existing lawful structures including the construction of water-tight window wells, elevating structures or the construction of flood walls or berms around residential, commercial or industrial principal structures where the outside toe of the floodwall or berm shall be no more than ten feet away from the exterior wall of the existing structure, and, which are not considered to be substantial improvements to the structure;
(k) The repair, replacement or reconstruction of a damaged building, provided that none of the outside dimensions of the building are increased and provided that the cost of repair is less than 50% of the building's value before it was damaged. When damage is 50% or more (a substantial improvement), the activity shall conform to § 151.062(C) of this chapter; and
(l) Modifications to an existing building that would not increase the enclosed floor area of the building below the BFE and which will not block flood flows. These modifications include fireplaces, bay windows, decks, patios and second story addition. No enclosed floor areas may be built on stilts. The modifications may not singularly or cumulatively equal 50% or more of the building's market value.
(2) Additions or changes to the above list of appropriate uses must be approved by the Committee prior to the adoption by the County Board and IDNR/OWR.
(3) All development in the regulatory floodway shall require a permit from IDNR-OWR and must be in accordance with all provisions of this chapter.
(4) Construction of an appropriate use will be considered permissible provided that the proposed project meets the following engineering and mitigation criteria and is so stated in writing with supporting plans, calculations and data prepared and signed by a professional engineer.
(a) All effective regulatory floodway conveyance lost due to the development of appropriate uses, other than bridge or culvert crossings or on-stream structures or dams, shall be replaced for all flood events up to and including the base flood.
(b) The following expansion and contraction ratios shall be used to determine transition sections in calculations of effective regulatory floodway conveyance.
1. Flowing water will expand no faster than at a rate of one foot horizontal for every four feet of the flooded stream's length.
2. Flowing water will contract no faster than at a rate of one foot horizontal for every one foot of the flooded stream's length.
3. Flowing water will not expand or contract faster than one foot vertical for every ten feet of flooded stream length.
4. All cross-sections used in the calculations shall be located perpendicular to flood flows.
5. Transition sections must be used to determine the effective conveyance areas on adjacent properties.
(c) Development of an appropriate use will not result in an increase in the average channel or regulatory floodway velocities or stage. However, in the case of bridges or culverts or on stream structures built for the purpose of backing up water in the stream during normal or flood flows, velocities may be increased at the structure site if scour, erosion and sedimentation will be avoided by the use of rip-rap or other design measures.
(5) In the case of on-stream structures built for the purpose of backing up water during normal or flood flows, the increase in flood stage when compared to existing conditions for all storm events up to and including the base flood event shall be contained within recorded easements or the channel banks. A dam safety permit or letter indicating a dam safety permit is not required must be obtained from IDNR/OWR for the structures.
(6) IDNR/OWR will issue permits for any IDNR/OWR projects, dams and the like and for all other state, WCSMC or certified community projects.
(Ord. 18-08, passed 1-14-19)