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R322.1.4 Establishing the Design Flood Elevation
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The design flood elevation shall be used to define flood hazard areas. At a minimum, the design flood elevation shall be the higher of the following:
Flood hazard areas shall be established in accordance with Table R301.2(1) footnote g.- The base flood elevation at the depth of peak elevation of flooding, including wave height, that has a 1 percent (100-year flood) or greater chance of being equaled or exceeded in any given year; or
- The elevation of the design flood associated with the area designated on a flood hazard map adopted by the community, or otherwise legally designated.
If design flood elevations are not specified, the building official is authorized to require the applicant to comply with either of the following:
- Obtain and reasonably use data available from a federal, state or other source; or
- Determine the design flood elevation in accordance with accepted hydrologic and hydraulic engineering practices used to define special flood hazard areas. Determinations shall be undertaken by a registered design professional who shall document that the technical methods used reflect currently accepted engineering practice. Studies, analyses and computations shall be submitted in sufficient detail to allow thorough review and approval.
Exception: Where it is not possible to obtain a DFE in accordance with Section R322.1.4.1
Items 1 and 2, the DFE shall be 3' (914 mm) above the highest adjacent grade, where the
highest adjacent grade is the natural ground elevation within the perimeter of the proposed
building prior to construction.
For the purpose of applying this code and ASCE 24, in all instances where this code or ASCE 24
specifies a construction requirement or building elevation requirement based on the Design
Flood Elevation (DFE) determined in accordance with Sections R322.1.4 or R322.1.4.1, such
construction requirement or building elevation requirement shall be interpreted to mean the
DFE determined in accordance with such section plus a freeboard of 2' (610 mm).
Exception: Freeboard shall not be required when the exception to Section R322.1.4.1 has
been applied.
In riverine flood hazard areas where design flood elevations are specified but floodways have not been designated, the applicant shall demonstrate that the effect of the proposed buildings and structures on design flood elevations, including fill, when combined with other existing and anticipated flood hazard area encroachments, will not increase the design flood elevation more than 1 foot (305 mm) at any point within the jurisdiction.
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R324.1.3 Building Planning, Establishing the Design Flood Elevation
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In riverine flood hazard areas where design flood elevations are specified but floodways have not been designated, the applicant shall demonstrate ...
Residential Code 2015 of New York State > 3 Building Planning > R322 Flood-Resistant Construction > R322.1 General > R322.1.4 Establishing the Design Flood Elevation > R322.1.4.2 Determination of Impacts