(A) The Floodplain District shall include areas subject to inundation by waters of the 1% annual chance flood. The basis for the delineation of the district shall be by the special flood hazard area elevations or profiles contained in the flood insurance study (FIS) and the flood insurance rate maps (FIRM) for the county, prepared by the Federal Emergency Management Agency, Federal Insurance Administration dated April 16, 2015 as amended.
(B) The county may identify and regulate local flood hazard or ponding areas that are not delineated on the FIRM. These areas may be delineated on a “local flood hazard map” using best available topographic data and locally derived information such as flood of record, historic high water marks or approximate study methodologies.
(C) The boundaries of the Floodplain Districts are established as shown on the FIRM which is declared to be a part of this chapter and which shall be kept on file at the county offices.
(1) The approximated floodplain area shall be that floodplain area for which no detailed flood profiles or elevations are provided, but where a 100-year floodplain boundary has been approximated. Such areas are shown as Zone A on the maps accompanying the flood insurance study. For these areas, the 100-year flood elevations from federal, state, and other acceptable sources shall be used, when available. Where the specific 100-year flood elevation cannot be determined for this area using other sources of data, such as the U.S. Army Corps of Engineers Floodplain Information Reports, U.S. Geological Survey Flood-Prone Quadrangles, etc., then the applicant for the proposed use, development, and/or activity shall determine this elevation in accordance with hydrologic and hydraulic engineering techniques. Hydrologic and hydraulic analyses shall be undertaken only by professional engineers or others of demonstrated qualifications, who shall certify that the technical methods used correctly reflect currently accepted technical concepts. Studies, analyses, computations, etc., shall be submitted in sufficient detail to allow a thorough review by the county.
(2) (a) The Special Floodplain District shall be those areas identified as an AE Zone on the maps accompanying the flood insurance study for which 100-year flood elevations have been provided but for which no floodplain has been delineated.
(b) Until a regulatory floodway is designated, no new construction, substantial improvements, or other development (including fill) shall be permitted within the areas of special flood hazard, designated as Zones A1-30 and AE or AH on the FIRM, unless it is demonstrated that the cumulative effect on the proposed development, when combined with all other existing and anticipated development, will not increase the water surface elevation of the base flood more than one foot at any point within the county.
(c) Development activities in Zones A1-30 and AE or AH, on the (community's) FIRM which increase the water surface elevation of the base flood by more than one foot may be allowed, provided that the applicant first applies - with the county's endorsement - for a conditional letter of map revision, and receives the approval of the Federal Emergency Management Agency.
(d) The requirements in 44 C.F.R. 60.3(c)(10) only applies along rivers, streams, and other watercourses where FEMA has provided base flood elevations. The requirement does not apply along lakes, bays and estuaries, and the ocean coast.
(3) (a) The Coastal A Zone shall be those areas, as defined by the VA USBC, that are subject to wave heights between one and one-half feet and three feet, and identified on the FIRM by the limit of moderate wave action (LIMA) line.
(4) The VE or V Zones on FIRMS accompanying the FIS shall be those areas that are known as coastal high hazard areas, extending from offshore to inland limit of a primary frontal dune along an open coast. For these areas, the following provisions shall apply (44 C.F.R. § 60.3 (e)):
(a) All new construction and substantial improvements in Zones V and VE (V if base flood elevation is available) shall be elevated on pilings or columns so that:
1. The bottom of the lowest horizontal structure member of the lowest floor (excluding the pilings or columns) is elevated to or above the base flood level (recommended 18 inches) if the lowest horizontal structure member is parallel to the direction of wave approach or elevated at least one foot above the base flood level if the lowest horizontal structural member is perpendicular to the direction of the wave approach: and
2. The pile or column foundation and structure attached thereto is anchored to resist floatation, collapse, and lateral movement due to the effects of wind and water loads acting simultaneously on all building components. Wind and water loading values shall each have a 1% chance of being equaled or exceeded in any given year (1% annual chance).
(b) A registered professional engineer or architect shall develop or review the structural design, specifications and plans for the construction, and shall certify that the design and methods of construction to be used are in accordance with accepted standards of practice for meeting the provisions of Article III, Section A 6 a.
(c) The Floodplain Administrator shall obtain the elevation (in relation to the mean sea level) of the bottom of the lowest horizontal structural member of the lowest floor (excluding pilings and columns) of all new and substantially improved structures in Zones V and VE. The Floodplain Administrator shall maintain a record of all such information.
(d) All new construction shall be located landward of the reach of mean high tide.
(e) All new construction and substantial improvements shall have the space below the lowest floor either free of obstruction or constructed with non-supporting breakaway walls, open wood-lattice work, or insect screening intended to collapse under wind and water loads without causing collapse, displacement, or other structural damage to elevated portions of the building or to the supporting foundation system. For the purpose of this section, the breakaway wall shall have a design safe loading resistance of not less than 10 pounds and no more than 20 pounds per square foot. Use of breakaway walls which exceed a design safe loading limit of 20 pounds per square foot (either by design or when so required by local codes) may be permitted only if a registered professional engineer or architect certifies that the designs proposed meet the following conditions:
1. Breakaway wall collapse shall result from water load less than that which would occur during the base flood; and
2. The elevated portion of the building and supporting foundation system shall not be subject to collapse, displacement, or other structural damage due to the effects of wind and water loads acting simultaneously on all building components (structural and non-structural). Maximum wind and water loading values to be used in this determination shall each have a 1% chance of being equaled or exceeded in any given year.
(f) The enclosed space below the lowest floor shall be used solely for parking of vehicles, building access, or storage. Such space shall not be partitioned into multiple rooms, temperature controlled, or used for human habitation.
(g) The use of fill for structural support of buildings is prohibited. When non-structural fill is proposed in a coastal high hazard area, appropriate engineering analyses shall be conducted to evaluate the impacts of the fill prior to issuance of a development permit.
(h) The man-made alteration of sand dunes, which would increase potential flood damage, is prohibited.
(5) The AO Zone on the FIRM accompanying the FIS shall be those areas of shallow flooding identified as AO on the FIRM. For these areas, the following provisions shall apply (44 C.F.R. § 60.3(c)):
(a) All new construction and substantial improvements of residential structures shall have the lowest floor, including basement, elevated 18 inches or above the flood depth specified on the FIRM, above the highest adjacent grade at least as high as the depth number specified in feet on the FIRM. If no flood depth number is specified, the lowest floor, including basement, shall be elevated no less than two feet above the highest adjacent grade.
(b) All new construction and substantial improvements of non-residential structures shall:
1. Have the lowest floor, including basement, elevated 18 inches or above the flood depth specified on the FIRM, above the highest adjacent grade at least as high as the depth number specified in feet on the FIRM. If no flood depth number is specified, the lowest floor, including basement, shall be elevated at least two feet above the highest adjacent grade; or
2. Together with attendant utility and sanitary facilities be completely flood-proofed to the specified flood level so that any space below that level is watertight with walls substantially impermeable to the passage of water and with structural components having the capability of resisting hydrostatic and hydrodynamic loads and effects of buoyancy.
(c) Adequate drainage paths around structures on slopes shall be provided to guide floodwaters around and away from proposed structures.
(Ord. passed - -20 )