In all areas of special flood hazard within the Regent Park Floodplain Overlay District where base flood elevation data has been provided pursuant to § 151.04(B) or as outlined in the duties and responsibilities of the local administrator in § 151.24, the requirements of § 151.35 shall apply in addition to the following higher general standards:
(A) Critical development.
(1) Existing critical development, if it cannot be reconstructed outside of the 500-year area of special flood hazard as part of development, shall be elevated or floodproofed to either (1) the 500-year flood elevation, or (2) the freeboard elevation above the base flood elevation pursuant to § 151.44(A), whichever is greater. If no data exists establishing the 500-year flood elevation or the highest known historical flood elevation, the applicant shall provide a hydrologic and hydraulic engineering analysis that generates 500-year flood elevation data in compliance with § 151.37.
(2) New critical development shall not be permitted to be located within the 500-year area of special flood hazard.
(D) Storage or stockpile of hazardous materials. Facilities, located within an area of special flood hazard and used for the storage or stockpiling of hazardous materials meeting minimum reportable quantities pursuant to the Emergency Planning and Community Right-to-Know Act (EPCRA) and 40 CFR Part 370, shall comply with requirements of the International Building Code (IBC), the International Residential Code (IBC), and ASCE 24-14 Flood Resistant Design and Construction, as applicable, and with the freeboard requirements.
(E) Dam breach analysis.
(1) Plans for proposed development, located downstream of an existing dam or include construction of a new dam as part of the development, shall show the inundation boundary that may result from a dam breach failure. Inundation boundaries shall be provided for any dam meeting the size and/or hazard potential classifications pursuant to S.C. Reg 72-2 of the South Carolina Dams and Reservoirs Safety Act Regulations, or any dam as otherwise identified by the local administrator. Inundation boundaries provided by the SCDHEC Dam Safety Program may be utilized to fulfill this requirement. If the entire proposed development's property is not located within a dam breach failure inundation boundary, the plans shall include a statement that the development is not located within a dam breach failure inundation boundary.
(2) If development is proposed to be located downstream of an existing dam that has not been provided with dam breach modeling and inundation mapping as made available by the SCDHEC Dam Safety Program, the development plans shall provide a dam failure or breach analysis with an inundation boundary.
(4) A dam breach analysis shall be prepared using BREACH, HEC-HMS, or HEC-RAS (unsteady flow), DAMBRK, DSS-WISE™, or other South Carolina Dam Safety Program approved equivalent engineering dam break flood model and mapping software. Flood routings must be performed using HEC-RAS (unsteady flow), FLDWAV, and DAMBRK. The applicant shall be responsible for determining the appropriate dam breach parameters so a breach outflow analysis can be developed and a resultant hydrograph routed downstream through the area of new development.
(5) The dam breach analysis method shall be prepared by a registered professional engineer, licensed in the State of South Carolina, and demonstrate the “sunny day” failure scenario for a “complete and sudden” breach while the impoundment level is at the principal spillway crest or maximum impoundment. The “sunny day” dam failure scenario represents an “any given day” type of breach that is NOT hydrologically induced (i.e., not rainfall driven), but is more likely caused by some weakness in the dam that may have gone unnoticed. A "complete and sudden" breach implies a failure where the entire dam is removed instantaneously at a point in time in the simulation.
(6) Proposed development located within an inundation area shall meet the minimum requirements of § 151.36(A) through (F), as applicable, as long as:
(a) Surface flow within the inundation area is not unduly restricted,
(b) Development does not increase the hazard classification of the dam,
(c) Development does not increase the potential for loss of life or property damage within the dam breach analysis inundation zone.
(7) A dam breach analysis shall not apply to the use of any building or structure in existence as of the effective date of this chapter, nor shall it prevent the restoration of a damaged building or structure, or prevent the continuance of the use of such building or part thereof as such use existed at the time of such damage, but shall apply to any alteration of a building that provides for a change in such use of any building after the effective date of this chapter.
(Ord. 2924, passed 6-3-24)