Sec. 9.3.9. Streets in Special Flood Hazard Areas

  1. All streets in SFHAs shall be designed and constructed to provide a minimum of two (2) feet of vertical freeboard, as measured from the predicted 10-year flood peak water surface elevation to the low point of the top of curb or edge of pavement for streets without curbs. All throughfares in SFHAs shall be designed and constructed so as not to be overtopped during the predicted 50-year storm. All other streets in SFHAs shall be designed and constructed so as not to be overtopped during the predicted 25-year storm. Exceptions may be granted to projects meeting at least one of the following conditions:
    1. When the Engineering Services Department finds those portions of streets within allowable City or State of NC Transportation vertical and horizontal controls which act as a transition to existing streets.
    2. When the City Council finds that the public benefit derived from the construction of the thoroughfare or collector street would be better served if these standards were varied.
  2. For any street in SFHAs, any proposed increase above floodway levels specified in the FIS for Wake County or Durham County, whichever is applicable may be allowed, provided that the change is approved by the Federal Insurance and Mitigation Administration.
  3. Any proposed street or driveway, bridge or culvert associated with a street or driveway (including fill), located in a SFHA must be accompanied by a sealed written statement by a registered professional engineer licensed in the State of North Carolina certifying that such structure is designed and constructed in accordance with this section and shall specify which provision applies.
  4. Outside of inundation areas designated in the National Inventory of Dams, the maximum depth of any overtopping flow during the predicted 100-year flood shall not exceed one (1) foot for a privately maintained street. For all public streets located outside of the inundation areas designated in the National Inventory of Dams, no overtopping is allowed during the predicted 100-year flood. The downstream slope of the roadway section shall be protected from erosion due to the overtopping flow. Public streets located within inundation areas designated in the National Inventory of Dams must be located at or above the 100- year flood elevation, consistent with the regulations of Sec. 9.3.6.B.