Secondary and Cumulative Impacts Master Management Plan - 2014

APPENDIX B – WAKE COUNTY PROGRAMS TO MITIGATE SECONDARY AND CUMULATIVE IMPACTS

In addition the encroachment must be proven (usually through a flood study) to not adversely affect existing or proposed onsite structures or offsite properties. In FEMA-identified Special Flood Hazard Areas, where a detailed flood study has already been performed, 100-year flood limits and elevations, as well as the floodway have been delineated; therefore, an additional flood study is not needed. Where FEMA has not performed a detailed flood study, the entire floodplain area is considered to be a floodway until a flood study is performed at the applicant’s expense. In new, detailed study areas and limited, detailed study areas (which are unnumbered “A” Zones), FEMA mapping will illustrate the 100-year floodplain under existing and future (buildout) conditions throughout Wake County. As a result, more than half of the river miles and associated floodplains in the Wake County jurisdiction will be mapped with future conditions (100-year floodplain noted). After completion of this process, a change to the UDO will occur that will restrict uses (including solid water disposal facilities, hazardous waste management facilities, salvage yards, and chemical storage facilities) in the future floodplain areas and require structures to be elevated above future floodplain elevations. Hazard Mitigation Plan The County’s 2004 Hazard Mitigation Plan and its 2009 update were developed in an effort to be eligible to receive federal and State disaster relief funds if a natural disaster occurred. The plan includes hazard mitigation strategies, including for flooding-related natural disasters. An implementation schedule is also included and the County is working through the implementation activities (Wake County, 2010b). An update to the county’s Hazard Mitigation Plan is currently under way which will result in the creation of a consolidated, multi-jurisdictional Hazard Mitigation Plan for the county and all twelve municipalities. B.6 Water Supply Watershed Protection Regulations A large portion of the County is within Water Supply Watersheds (WSWs), a majority of which is zoned as residential. The County has established limitations on impervious surface areas and densities within the WSWs primarily through zoning districts R-40w and R-80W for residential development, presented in Article 5 of the UDO. The County also has zoning overlay districts for the few areas in WSWs that are non-residential, presented in Articles 3 and 11 of the UDO. If there is a conflict between provisions within these two articles, then the most strict limitations apply. Special buffer requirements for Water Supply Watersheds are discussed in section B.5. All residential development in the county is limited to 30 percent impervious surface coverage regardless of the watershed. Zoning districts R-80W and R-40W have impervious surface limitation include for non-residential development of 6 and 12 percent respectively, with allowance of up to 24 percent if the first 0.5 inch of rainfall is retained on site. Additionally, in these zoning districts, densities are limited to 0.5 units per acre for R-80W and 1.0 unit per acre for R-40W. WSW Overlay District WS-III, which in the Swift Creek Watershed, has an impervious surface limitation of 12 percent are applied, but these impervious surface limits are not

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