Okla. Admin. Code § 785:55-3-4

Current through Vol. 42, No. 4, November 1, 2024

Section 785:55-3-4 - General requirements for development in any regulatory floodplain

(a)Applicability of section. The provisions of this section shall apply to development within any regulatory floodplain, regardless of whether base flood elevations have been determined or regulatory floodways have been delineated.

(b)Temporary fills. Temporary fills, such as cofferdams or fills used during construction, may be used upon assumption of full responsibility by the sponsoring agency.

(c)Roadways, bridges and public utilities within the regulatory floodplain. For roadways, bridges and public utilities within the regulatory floodplain, the following shall apply:

(1) When failure or interruption of service of roadways, bridges, or public utilities would endanger public health or safety, such roadways, bridges, or public utilities shall be protected to the base flood elevation or to the elevation of the flood of record, whichever is greater. In other instances where only economic losses are threatened, protection shall be provided to the extent practical. A degree of protection less than the base flood elevation may be justified even in cases where overtopping could occur.

(2) The following provisions shall apply to all applicable construction:

(A) Buried crossings such as pipelines shall be maintained at least three (3) feet below the channel bottom.

(B) Modification, addition and replacement of existing roadways, bridges and public utilities shall be allowed providing adequate provision is made for the backwater effects of new flow obstructions in accordance with 785:55-3-1, 785:55-3-2, and 785:55-3-3.

(d)Storage of materials. Materials that are buoyant, flammable, explosive, or could be injurious to human, animal or plant life shall be stored above the base flood elevation, floodproofed or protected by structural measures consistent with the standards set forth herein. Storage of materials likely to cause water pollution, in the event of flooding, is prohibited unless adequate safeguards are provided.

(e)Emergency repairs and replacements. Emergency repairs and replacements which will not threaten public health or safety may be built or constructed without a permit. If the construction would normally require a permit, application for such permit must be made as soon as practical. Construction must be removed if it does not conform to the rules in this Chapter.

(f)Government projects. Government projects for flood damage control or other water management purposes otherwise authorized by law shall be allowed under the following conditions:

(1) The project does not increase flood damage potential.

(2) Any increase in flooding above, below or through the project area is mitigated by project design.

(3) Plans, specifications and provisions for securing required land rights have been approved and a development permit issued by the Board; and

(4) A sponsoring agency is authorized and has accepted full responsibility for operations, maintenance and repair of the project.

(g)Dikes, levees, floodwalls and similar structures. For dikes, levees, floodwalls and similar structures, the following shall apply:

(1) Protection afforded by existing dikes, levees, floodwalls and similar structures will be evaluated during delineation of the regulatory floodplain. If the existing levee provides protection to the base flood elevation, to include at least 3 feet of freeboard, the boundary of the regulatory floodplain will be located channelward of the levee. Regulatory floodplains will then be delineated along interior streams, based on their regulatory flood discharge. If the existing levee does not provide protection to the base flood elevation, the regulatory floodplain will be delineated as if the levee does not exist.

(2) Construction of new levees may be allowed as a government project as provided in (f) of this section. Protection must be provided equivalent to that provided by filling to the base flood elevation.

(h)Reservoir or channel improvements. The regulatory floodplain shall not be changed on the basis of proposed reservoir or channel improvements. The regulatory floodplain may be changed after the reservoir or channel improvements are constructed and operative. All requests to change the regulatory floodplain boundaries must be submitted through the Board to FEMA for approval.

(i)Error in delineation of the regulatory floodplain. The delineation of the regulatory floodplain shall not be changed unless it has been shown that the original delineation is in error or there are changed conditions which modify the original computations. Any person contesting the correctness of the delineation shall be given reasonable opportunity to submit his own technical evidence. Such evidence along with a request to change shall be forwarded to FEMA through the Board for consideration.

(j)Methods for providing flood protection. The following are nonexclusive acceptable methods for providing flood protection:

(1) Permanent fill may be allowed as a means of providing safe construction sites, provided:

(A) The fill, except in exceptional circumstances, is contiguous with the boundary of the regulatory floodplain and shaped, in plan, so as not to create adverse velocities or current patterns.

(B) The surface of the fill is above the regulatory flood elevation.

(C) The channelward face of the fill shall be protected against erosion. If protected by vegetative cover, slopes shall be no steeper than three (3) horizontal to one (1) vertical. Steeper slopes shall be protected by riprap. A vertical bulkhead may be used if adequatley founded and protected against scour.

(D) Fill shall be of suitable material and so compacted to provide adequate support under saturated conditions.

(E) Adequate provision is made for conducting drainage across or through the fill.

(2) Elevating on adequately anchored pilings or columns is allowed provided:

(A) The lowest portion of the structural members of the lowest floor (excluding the pilings and columns) is elevated one-foot above the base flood elevation and securely anchored to such piles or columns.

(B) The elevating members are designed to withstand saturated conditions, hydrostatic pressure, and to minimize scouring.

(C) The size, shape, spacing and alignment of elevating members are selected to minimize turbulence and deflection of current patterns, and to facilitate easy passage of debris.

(D) Major access and utility services are elevated at least one (1) foot above the base flood elevation.

(k)Channel relocation and modification. Channel relocation and modification may be allowed provided the upstream and downstream flood potential is not altered.

(l)New storm cellars. For new storm cellars, the following shall apply:

(1) New storm cellars may be built below the flood elevation provided that such new storm cellars are:

(A) Limited to nonhabitable uses,

(B) Designed so that all electrical, heating and other mechanical equipment is above the regulatory flood protection level.

(C) Designed so that hydrostatic pressure and uplift forces are unable to dislodge structure from the ground and the integrity of the storm cellar is preserved during the flooding.

(2) Compliance with requirements of (1) (A) through (C) of this subsection must be certified by a Registered Professional Engineer or Licensed Architect.

Okla. Admin. Code § 785:55-3-4

Amended at 10 Ok Reg 3369, eff 6-25-93; Amended at 14 Ok Reg 2808, eff 7-1-97