In all areas of special flood hazards, the following standards
are required:
A.
Anchoring.
(1)
All new construction and substantial improvements shall be anchored
to prevent flotation, collapse, or lateral movement of the structure.
(2)
All manufactured homes shall be installed using methods and practices
which minimize flood damage. Manufactured homes must be elevated and
anchored to resist flotation, collapse, or lateral movement. Manufactured
homes shall be elevated to or above the base flood elevation or two
feet above the highest adjacent grade when no base flood elevation
has been determined. Methods of anchoring may include, but are not
to be limited to, use of over-the-top or frame ties to ground anchors.
This requirement is in addition to applicable state and local anchoring
requirements for resisting wind forces.
B.
Construction materials and methods.
C.
Utilities.
(1)
Electrical, heating, ventilation, plumbing, air-conditioning equipment,
and other service facilities shall be designed and/or located so as
to prevent water from entering or accumulating within the components
during conditions of flooding. When designed for location below the
base flood elevation, a professional engineer's or architect's
certification is required;
(2)
All new and replacement water supply systems shall be designed to
minimize or eliminate infiltration of floodwaters into the system;
(3)
New and replacement sanitary sewage systems shall be designed to
minimize or eliminate infiltration of floodwaters; and
(4)
On-site waste disposal systems shall be located to avoid impairment
to them or contamination from them during flooding.
D.
Subdivision proposals.
(1)
All subdivision proposals shall be consistent with the need to minimize
flood damage;
(2)
All subdivision proposals shall have public utilities and facilities
such as sewer, gas, electrical, and water systems located and constructed
in minimize flood damage;
(3)
All subdivision proposals shall have adequate drainage provided to
reduce exposure to flood damage; and
(4)
Base flood elevation data shall be provided for subdivision proposals
and other proposed developments (including proposals for manufactured
home parks and subdivisions) greater than either 50 lots or five acres.
E.
Encroachments.
(1)
All proposed development in riverine situations where no flood elevation data is available (unnumbered A Zones) shall be analyzed to determine the effects on the flood-carrying capacity of the area of special flood hazards set forth in § 93-12A, Permit application review. This may require the submission of additional technical data to assist in the determination.
(2)
In all areas of special flood hazard in which base flood elevation data is available pursuant to § 93-12B or Subsection D(4) of this section and no floodway has been determined the cumulative effects of any proposed development, when combined with all other existing and anticipated development, shall not increase the water surface elevation of the base flood more than one foot at any point.
In all areas of special flood hazards where base flood elevation data has been provided as set forth in § 93-6, Basis for establishing areas of special flood hazard, and § 93-12B, Use of other base flood and floodway data, the following standards are required:
A.
Residential construction. New construction and substantial improvements
of any resident structure shall:
(1)
Have the lowest floor, including basement or cellar, elevated to
or above the base flood elevation;
(2)
Have fully enclosed areas below the lowest floor that are subject
to flooding designed to automatically equalize hydrostatic flood forces
on exterior walls by allowing for the entry and exit of floodwaters.
Designs for meeting this requirement must either be certified by a
licensed professional engineer or architect or meet or exceed the
following minimum criteria:
(a)
A minimum of two openings having a total net area of not less
than one square inch for every square foot of enclosed area subject
to flooding;
(b)
The bottom of all such openings shall be no higher than one
foot above the lowest adjacent finished grade; and
(c)
Openings may be equipped with louvers, valves, screens or other
coverings or devices provided they permit the automatic entry and
exit of floodwaters.
B.
Nonresidential construction.
(1)
New construction and substantial improvements of any commercial,
industrial or other nonresidential structure, together with attendant
utility and sanitary facilities, shall either: have the lowest floor,
including basement or cellar, elevated to or above the base flood
elevation; or be floodproofed so that the structure is watertight
below the base flood level with walls substantially impermeable to
the passage of water. All structural components located below the
base flood level must be capable of resisting hydrostatic and hydrodynamic
loads and the effects of buoyancy.
(a)
If the structure is to be elevated, fully enclosed areas below
the base flood elevation shall be designed to automatically (without
human intervention) allow for the entry and exit of floodwaters for
the purpose of equalizing hydrostatic flood forces on exterior walls.
Designs for meeting this requirement must either be certified by a
licensed professional engineer or a licensed architect or meet the
following criteria:
[1]
A minimum of two openings having a total net area of not less
than one square inch for every square foot of enclosed area subject
to flooding;
[2]
The bottom of all such openings shall be no higher than one
foot above the lowest adjacent finished grade; and
[3]
Openings may be equipped with louvers, valves, screens or other
coverings or devices, provided they permit the automatic entry and
exit of floodwaters.
(b)
If the structure is to be floodproofed:
[1]
A licensed professional engineer or architect shall develop
and/or review structural design, specifications, and plans for the
construction, and shall certify that the design and methods of construction
are in accordance with accepted standards of practice to make the
structure watertight with walls substantially impermeable to the passage
of water, with structural components having the capability of resisting
hydrostatic and hydrodynamic loads and effects of buoyancy; and
[2]
A licensed professional engineer or licensed land surveyor shall
certify the specific elevation (in relation to mean sea level) to
which the structure is floodproofed.
(2)
The local administrator shall maintain on record a copy of all such
certificates noted in this section.
C.
Construction standards for areas of special flood hazards without base flood elevations. New construction or substantial improvements of structures including manufactured homes shall have the lowest floor including basement elevated to or above the base flood elevation as may be determined in § 93-12B or two feet above the highest adjacent grade where no elevation data is available.
(1)
New construction or substantial improvements of structures including
manufactured homes shall have the lowest floor (including basement)
elevated at least two feet above the highest adjacent grade next to
the proposed foundation of the structure.
(2)
Fully enclosed areas below the lowest floor that are subject to flooding
shall be designed to automatically (without human intervention) allow
for the entry and exit of floodwaters for the purpose of equalizing
hydrostatic flood forces on exterior walls. Designs for meeting this
requirement must either be certified by a licensed professional engineer
or a licensed architect or meet the following criteria:
(a)
A minimum of two openings having a total net area of not less
than one square inch for every square foot of enclosed area subject
to flooding;
(b)
The bottom of all such openings shall be no higher than one
foot above the lowest adjacent finished grade;
(c)
Openings may be equipped with louvers, valves, screens or other
coverings or openings provided they permit the automatic entry and
exit of floodwaters.
Located within areas of special flood hazard are areas designated as floodways (see § 93-2, Definitions). The floodway is an extremely hazardous area due to high-velocity floodwaters carrying debris and posing additional threats from potential erosion forces. When floodway data is available for a particular site as provided by §§ 93-6 and 93-12B, all encroachments including fill, new construction, substantial improvements, and other development are prohibited within the limits of the floodway unless a technical evaluation demonstrates that such encroachments shall not result in any increase in flood levels during the occurrence of the base flood discharge.
