§ 90-723. Description of special flood hazard districts.

(a)

Basis of districts. The various special flood hazard districts shall include the SFHAs. The basis for the delineation of these districts shall be the FIS and the FIRM for the County of Prince George as prepared by the Federal Emergency Management Agency, Federal Insurance Administration, dated May 16, 2012, and any subsequent revisions or amendments thereto.

The County of Prince George 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 the best available topographic data and locally derived information such as flood of record, historic high water marks or approximate study methodologies.

The boundaries of the SFHA districts are established as shown on the FIRM which is declared to be a part of this ordinance and which shall be kept on file at the County of Prince George offices.

1.

The floodway district is in an AE Zone and is delineated, for purposes of this ordinance, using the criterion that certain areas within the floodplain must be capable of carrying the waters of the one percent annual chance 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 Table 3 of the above-referenced FIS and shown on the accompanying FIRM.

The following provisions shall apply within the floodway district of an AE zone:

(a)

Within any floodway area, no encroachments, including fill, new construction, substantial improvements, or other development shall be permitted unless it has been demonstrated through hydrologic and hydraulic analysis performed in accordance with standard engineering practice that the proposed encroachment will not result in any increase in flood levels within the community during the occurrence of the base flood discharge. 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 floodplain administrator.

Development activities which increase the water surface elevation of the base flood may be allowed, provided that the applicant first applies with the County of Prince George's endorsement for a Conditional Letter of Map Revision (CLOMR), and receives the approval of the Federal Emergency Management Agency.

If section 90-723(a)1(a) is satisfied, all new construction and substantial improvements shall comply with all applicable flood hazard reduction provisions of section 90-725.

(b)

The placement of manufactured homes (mobile homes) is prohibited, except when replacing an existing manufactured home (mobile home) in an existing manufactured home park or subdivision. A replacement manufactured home (mobile home) may be placed on a lot in an existing manufactured home park or subdivision provided the anchoring, elevation and encroachment standards are met.

2.

The AE, or AH Zones on the FIRM accompanying the FIS shall be those areas for which one-percent annual chance flood elevations have been provided and the floodway has not been delineated.

The following provisions shall apply within an AE or AH zone:

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 of 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 of Prince George.

Development activities in Zones Al-30 and AE or AH, on the County of Prince George'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 of Prince George's endorsement for a conditional letter of map revision, and receives the approval of the federal emergency management agency.

3.

The A zone on the FIRM accompanying the FIS shall be those areas for which no detailed flood profiles or elevations are provided, but the one percent annual chance floodplain boundary has been approximated. For these areas, the following provisions shall apply:

The approximated floodplain district shall be that floodplain area for which no detailed flood profiles or elevations are provided, but where a one hundred (100)-year floodplain boundary has been approximated. Such areas are shown as Zone A on the maps accompanying the FIS. For these areas, the base flood elevations and floodway information from federal, state, and other acceptable sources shall be used, when available. Where the specific one percent annual chance 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 base flood elevation. For development proposed in the approximate floodplain the applicant must use technical methods that correctly reflect currently accepted, non-detailed, technical concepts, such as point on boundary, high water marks, or detailed methodologies hydrologic and hydraulic analyses. Studies, analyses, computations, etc., shall be submitted in sufficient detail to allow a thorough review by the floodplain administrator.

The floodplain administrator reserves the right to require a hydrologic and hydraulic analysis for any development. When such base flood elevation data is utilized, the lowest floor shall be elevated to at least one foot above the base flood level.

During the permitting process, the floodplain administrator shall obtain:

(1)

the elevation of the lowest floor, including the basement, of all new and substantially improved structures; and,

(2)

if the structure has been flood-proofed in accordance with the requirements of this article, the elevation in relation to mean sea level to which the structure has been flood-proofed.

Base flood elevation data shall be obtained from other sources or developed using detailed methodologies comparable to those contained in an FIS for subdivision proposals and other proposed development proposals including manufactured home parks and subdivisions that exceed fifty lots or five acres, whichever is the lesser.

4.

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:

(a)

All new construction and substantial improvements of residential structures shall have the lowest floor, including the basement, elevated to 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 the basement, shall be elevated no less than two feet above the highest adjacent grade.

(b)

All new construction and substantial improvements of nonresidential structures shall:

(1)

have the lowest floor, including basement, elevated to 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.

5.

The coastal A zone 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 as areas of Limits of Moderate Wave Action (LiMWA). For these areas, the following provisions shall apply:

Buildings and structures within this zone shall have the lowest floor elevated to or above the base flood elevation plus one foot of freeboard, and must comply with the provisions in section 90-723(a)2 and sections 90-725 through 90-727.

6.

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 the inland limit of a primary frontal dune along an open coast. For these areas, the following provisions shall apply:

(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 structural member of the lowest floor, excluding the pilings or columns is elevated to at least one foot above the base flood level if the lowest horizontal structural 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 wave approach; and,

(2)

The pile or column foundation and structure attached thereto is anchored to resist flotation, 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 one percent chance of being equaled or exceeded in any given year as a one-percent 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 section 90-723(a)6(a).

(c)

The floodplain administrator shall obtain the elevation, in relation to 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 the elevated portion of the building or supporting foundation system. For the purpose of this section, a breakaway wall shall have a design safe loading resistance of not less than ten and no more than 20 pounds per square foot. The use of breakaway walls which exceed a design safe loading resistance 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, both structural and nonstructural. Maximum wind and water loading values to be used in this determination shall each have a one percent 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.

(Ord. No. O-12-07, 4-24-2012; Ord. No. O-15-09, § 2, 4-28-2015)

(Ord. No. O-12-07, 4-24-2012; Ord. No. O-15-09, § 2, 4-28-2015)