Unified Development Ordinance, 30th Supplement, November 2023

Article 9.3. ​Floodprone Area Regulations | CHAPTER 9. ​NATURAL RESOURCE PROTECTION

ii. Not redirect velocities of water onto impacted structures.

elevated or floodproofed in accordance with the standards in Sec. 11.4.6. and Sec. 9.3.5. b. When data is available from a federal, state, or other City-accepted source for unestablished FEMA floodway and non-encroachment areas all new construction and substantial improvements within these floodway and non-encroachment areas established from available data shall comply with the requirements of Sec. 9.3.6.A. c. All subdivision, manufactured home park and other development proposals shall provide BFE data if development is greater than five (5) acres or has more than fifty (50) lots/manufactured home sites. Such BFE data shall be adopted by reference in accordance with Sec. 9.3.3.B.1. and utilized in implementing this Article. d. When BFE data is not available from a federal, state, or other City accepted source as outlined above, the reference level shall be elevated or floodproofed (nonresidential) to or above the RFPE. All other applicable provisions of Sec. 9.3.5. shall apply. Sec. 9.3.7. SFHA Based on Drainage Basin Study and Flood Hazard Soils Standards A. Drainage Basin Study and Flood Hazard Soils Floodway Standards The following provisions shall apply to those areas designated as floodways based on drainage basin studies or flood hazard soils: 1. No encroachments, including fill, new construction, substantial improvements, and other developments shall be permitted unless: a. It is demonstrated that the proposed encroachment would not result in any increase in the flood levels during the occurrence of the base flood discharge, based on hydrologic and hydraulic analyses performed in accordance with standard engineering practice and presented to the Floodplain Administrator and/or his or her designee prior to issuance of flood permit. 2. If Sec. 9.3.7.A.1. is satisfied, all proposed development shall comply with all applicable flood hazard reduction standards in Sec. 9.3.5. 3. Provided they are not otherwise restricted activities per Sec. 9.3.7.A.1., the following structures and activities are allowed within drainage basin study and/or flood hazard soils-based floodway.

b) An administrative approval by the Floodplain Administrator and/or his or her designee for any redevelopment that does not increase the flood elevation and that decreases the bulk of an existing building or structure below the BFE or future conditions flood level by at least 25% of the portion exceeding 50% of the FEMA floodway fringe or FEMA future conditions flood hazard areas. Any additional fill or material being added as a part of the redevelopment shall be included for calculation of the bulk of the proposed redevelopment. A written request for an administrative approval shall be submitted to the Floodplain Administrator and/ or his or her designee.

d. Notwithstanding the preceding exceptions, a variance from the 50% lot coverage threshold in Sec. 9.3.6.B.3. may be sought by an applicant following the procedures prescribed in Sec.10.2.10. C. Standards for FEMA Designated SFHAs without FEMA Established BFEs and/or Floodways If development is proposed within a FEMA designated SFHA established in accordance with Sec. 9.3.3.B.1., where no BFE data has been provided by FEMA on the FIRM, the following provisions, in addition to the provisions of Sec. 9.3.5., shall apply: 1. No encroachments, including fill, new construction, substantial improvements or new development shall be permitted within a distance of twenty feet (20’) each side from top of bank or five times the width of the stream whichever is greater, unless certification with supporting technical data by a registered professional engineer licensed in the State of North Carolina is provided to the Floodplain Administrator and/or his or her designee demonstrating that such encroachments shall not result in any increase in flood levels during the occurrence of the base flood discharge. 2. The BFE used in determining the RFPE shall be determined based on the following criteria: a. When BFE data is available from other sources, all new construction and substantial improvements within areas without FEMA established BFEs shall comply with all applicable provisions of this Article and shall be

9 – 39 Published November 2023

Part 10: Unified Development Ordinance City of Raleigh, North Carolina

Supp. No. 30