A. 
Basis of districts. The floodplain district shall include special flood hazard areas. The basis for the delineation of the district shall be the Flood Insurance Study (FIS) and the Flood Insurance Rate Maps (FIRMs) for Northumberland County, Virginia, prepared by the Federal Emergency Management Agency, dated December 30, 2021, and any subsequent revisions or amendments thereto. Northumberland 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.
[Amended 11-10-2021]
B. 
District boundaries. The boundaries of the special flood hazard area and floodplain districts are established as shown on the Flood Insurance Rate Map which is declared to be a part of this chapter and which shall be kept on file at the Northumberland County Land Use offices.
(1) 
The Floodway District is in an AE Zone and is delineated, for purposes of this chapter, using the criterion that certain areas within the floodplain must be capable of carrying the waters of the one-hundred-year flood without increasing the water surface elevation of that flood more than one foot at any point. The areas included in this district are specifically defined in the above-referenced Flood Insurance Study and shown on the accompanying Flood Insurance Rate Map.
(2) 
The Special Floodplain District shall be those areas identified as an AE Zone on the maps accompanying the Flood Insurance Study for which one-hundred-year flood elevations have been provided.
(3) 
The Approximated Floodplain District shall be those areas identified as an A or A99 Zone on the maps accompanying the Flood Insurance Study. In these zones, no detailed flood profiles or elevations are provided, but the one-hundred-year floodplain boundary has been approximated. For these areas, the one-hundred-year flood elevations and floodway information from federal, state, and other acceptable sources shall be used, when available. Where the specific one-hundred-year flood elevation cannot be determined for this area using other sources of data, such as the United States Army Corps of Engineers Flood Plain Information Reports, United States 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 governing body.
(4) 
The Coastal High Hazard District shall be those areas identified as VE or V Zones on the maps accompanying the Flood Insurance Study.
C. 
Overlay concept.
(1) 
The floodplain district described above shall be overlays to the existing underlying area as shown on the Official Zoning Ordinance Map, and, as such, the provisions for the floodplain district shall serve as a supplement to the underlying district provisions.
(2) 
In any conflict between the provisions or requirements of the floodplain districts and those of any underlying district, the more restrictive provisions and/or those pertaining to the floodplain districts shall apply.
(3) 
In the event any provision concerning a floodplain district is declared inapplicable as a result of any legislative or administrative actions or judicial decision, the basic underlying provisions shall remain applicable.
(4) 
The Coastal A Zone District shall be those areas, as defined by the VA USBC, that are subject to wave heights between 1.5 feet and three feet, and identified on the FIRM by the limit of moderate wave action (LiMWA) line.
(5) 
The Shallow Flooding District shall be those areas identified as Zone AO on the FIRM.
The boundaries of the floodplain district are established as shown on the Flood Insurance Rate Map, which is declared to be a part of this chapter and which shall be kept on file at the Northumberland County Office of Building and Zoning.
The delineation of any of the floodplain districts may be revised by the Northumberland County Board of Supervisors where natural or man-made changes have occurred and/or where more detailed studies have been conducted or undertaken by the United States Army Corps of Engineers or other qualified agency, or an individual documents the need for such change. However, prior to any such change, approval must be obtained from the Federal Emergency Management Agency.
Initial interpretations of the boundaries of the floodplain district shall be made by the Zoning Administrator. Should a dispute arise concerning the boundaries of any of the districts, the Board of Zoning Appeals shall make the necessary determination. The person questioning or contesting the location of the district boundary shall be given a reasonable opportunity to present his case to the Board and to submit technical evidence if desired.
A community's base flood elevations may increase or decrease resulting from physical changes affecting flooding conditions. As soon as practicable, but not later than six months after the date such information becomes available, a community shall notify the Federal Emergency Management Agency of the changes by submitting technical or scientific data. Such a submission is necessary so that upon confirmation of those physical changes affecting flooding conditions, risk premium rates and floodplain management requirements will be based upon current data.