223 / 634
APPENDIX B – WAKE COUNTY PROGRAMS TO MITIGATE SECONDARY AND CUMULATIVE IMPACTS
B-15
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