Residential structures (except Coastal High Hazard Areas and Coastal A Zones).

A. Elevation. The following standards apply to new and substantially improved residential structures located in areas of special flood hazard, in addition to the requirements in § 170-15B , Subdivision and development proposals, § 170-15C , Encroachments, and § 170-16 , Standards for all structures.(1) Within Zones A1-A30, AE, AH if base flood elevation data are available, new construction and substantial improvements shall have the top of the lowest floor (including basement) elevated to or above two feet above the base flood elevation. Within Zones AH adequate drainage paths are required to guide floodwaters around and away from proposed structures on slopes.(2) Within Zone A, when no base flood elevation data are available, a base flood elevation shall be determined by either:(a) Obtain and reasonably use data available from a federal, state or other source plus two feet of freeboard, or(b) Determine the base flood elevation in accordance with accepted hydrologic and hydraulic engineering practice, plus two feet of freeboard.

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.(3) Within Zone AO, new construction and substantial improvements shall have the lowest floor (including basement) elevated above the highest adjacent grade at least as high as the depth number specified in feet on the community's Flood Insurance Rate Map enumerated in § 170-6 plus one foot of freeboard. In areas designated as Zone AO where a depth number is not specified on the map, the depth number shall be taken as being equal to two feet.

Within AO, adequate drainage paths are required to guide floodwaters around and away from proposed structures on slopes.