Sec. 565-302. - Basis for establishing the areas of special flood hazard.
The flood boundaries have been established from hydrological data delineated on flood insurance rate maps provided by the Federal Emergency Management Agency (FEMA) in a scientific and engineering report entitled "The Flood Insurance Study for Marion County, Indiana (All Jurisdictions)," dated April 19, 2016. Topographic-based floodplain maps that may be developed by the Consolidated City of Indianapolis and Marion and approved for use by FEMA may be used as best available data to supplement FEMA's flood insurance rate maps, in accordance with FEMA and IDNR procedures and regulations. These maps contain zone AE floodplain areas for which floodway boundaries and base flood elevations are provided, zone AH floodplain areas for which base flood elevations are provided, zone AO floodplain areas for which base flood elevations are not provided, and zone A floodplain areas for which floodway boundaries and base flood elevations are not provided. Each of those maps also contain shaded zone X floodplain areas that depict areas subject to flooding in the headwaters of a stream, the 500-year frequency floodplain collar outside of the 100-year frequency zone AE area, and land subject to shallow flood depths of less than one foot. The flood boundaries and base flood elevations for mapped areas shall be determined as follows:
(a) The regulatory flood elevation, floodway, and fringe limits for the studied SFHAs within the jurisdiction of the Consolidated City of Indianapolis and Marion County, Indiana (All Jurisdictions), delineated as an "AE Zone" on the Consolidated City of Indianapolis and Marion County, Indiana Flood Insurance Rate Map dated April 19, 2016 shall be determined from the one-percent annual chance flood profiles in the Flood Insurance Study of Marion County, Indiana (All Jurisdictions) and the corresponding Flood Insurance Rate Maps (FIRM) dated April 19, 2016 as well as any subsequent updates, amendments, or revisions, prepared by the Federal Emergency Management Agency with the most recent date. Should the floodway limits not be delineated on the Flood Insurance Rate Map for a studied SFHA designated as an "AE Zone", the limits of the floodway will be according to the best available flood layer as provided by the Indiana Department of Natural Resources.
(b) The regulatory flood elevation, floodway, and fringe limits for each of the SFHAs within the jurisdiction of the Consolidated City of Indianapolis and Marion, County, Indiana (All Jurisdictions), delineated as an "A Zone" on the Consolidated City of Indianapolis and Marion County, Indiana Flood Insurance Rate Map, dated April 19, 2016, as well as any subsequent updates, amendments, or revisions, prepared by the Federal Emergency Management Agency with the most recent date, shall be according to the best available flood layer provided by the Indiana Department of Natural Resources, provided the upstream drainage area from the subject site is greater than one square mile. Whenever a party disagrees with the best available flood layer data, the party needs to replace existing data with better data that meets current engineering standards. To be considered, this data must be submitted to the Indiana Department of Natural Resources for review and subsequently approved.
Zone AH and zone AO: In zone AH floodplain areas, the base flood elevation shown on the flood insurance rate map shall be used. In zone AO areas, the base flood elevation shall be determined by adding the depth number specified in feet on the flood insurance rate map (two feet, if no depth number is specified) to the highest ground elevation at the site.
Zone X: Zone X areas (shaded or unshaded) are not designated by FEMA as special flood hazard areas and are not regulated by this article.
(c) In the absence of a published FEMA map, or absence of identification on a FEMA map, the regulatory flood elevation, floodway, and fringe limits of any watercourse in the community's known flood prone areas shall be according to the best available flood layer as provided by the Indiana Department of Natural Resources, provided the upstream drainage area from the subject site is greater than one square mile. In the event IDNR lacks sufficient data, the floodplain administrator and/or designee shall determine which type of flood delineation the site is located in and the appropriate flood protection grade and limitations applicable to that area. If the floodplain administrator and/or designee lack sufficient data to make this determination, the applicant for the floodplain development permit shall be required to submit a floodplain delineation boundary determination completed by a registered professional engineer. The procedures by which specific determinations flood boundaries are to be made and incorporated into revisions of the flood insurance rate maps are set forth in Article 4 Map Maintenance.
(d) Upon issuance of a letter of final determination (LFD), the floodplain administrator and/or designee shall use more restrictive data in the new (not yet effective) mapping/study shall be utilized for permitting and construction (development) purposes, replacing all previously effective less restrictive flood hazard data provided by FEMA.
(G.O. 22, 2024, § 1)
