All new construction and substantial improvements having fully
enclosed areas below the lowest floor that are usable solely for parking
of vehicles, building access or storage in an area other than a basement
and which are subject to flooding shall be 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 registered professional engineer or
architect or must meet or exceed the following minimum criteria: 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
shall be provided. The bottom of all openings shall be no higher than
one foot above grade. Openings may be equipped with screens, louvers,
or other covering or devices, provided that they permit the automatic
entry and exit of floodwaters.
In all areas of special flood hazards where base flood elevation data has been provided as set forth in §
136-7, Basis for establishing areas of special flood hazard, or in §
136-15, Use of other base flood and floodway data, the following standards below are required.
In an area of special flood hazard, all new construction and
substantial improvement of any commercial, industrial or other nonresidential
structure shall have the lowest floor, including basement, together
with the attendant utilities and sanitary facilities, either elevated
to the level of the base flood elevation and, within any AO Zone on
the municipality's DFIRM, that all new construction and substantial
improvement of any commercial, industrial or other nonresidential
structure shall have the lowest floor, including basement, elevated
above the highest adjacent grade at least as high as the depth number
specified in feet (at least two feet if no depth number is specified),
and require adequate drainage paths around structures on slopes to
guide floodwaters around and away from proposed structures, or:
A. Be floodproofed so that below the base flood level the structure
is watertight with walls substantially impermeable to the passage
of water;
B. Have structural components capable of resisting hydrostatic and hydrodynamic
loads and effects of buoyancy; and
C. Be certified by a registered professional engineer or architect that the design and methods of construction are in accordance with accepted standards of practice for meeting the applicable provisions of this section. Such certification shall be provided to the official as set forth in §
136-12C.
Located within areas of special flood hazard established in §
136-7 are areas designated as floodways. Since the floodway is an extremely hazardous area due to the velocity of floodwaters which carry debris, potential projectiles, and erosion potential, the following provisions apply:
A. Prohibit encroachments, including fill, new construction, substantial
improvements, and other development, unless a technical evaluation
demonstrates that encroachment shall not result in any increase in
flood levels during the occurrence of the base flood discharge.
B. If §
136-31A is satisfied, all new construction and substantial improvements must comply with Article
V, Provisions for Flood Hazard Reduction.
C. In all areas of special flood hazard in which base flood elevation
data has been provided and no floodway has been designated, the cumulative
effect 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 0.2 of a foot at any point.