DIGITAL KARST LAYER AND COMPILATION OF MAPPED KARST (SINKHOLE) FEATURES IN NEW HANOVER AND BRUNSWICK COUNTIES, NORTH CAROLINA – RELATIONSHIP TO CRITICAL FACILITIES

Ground collapse and subsidence from limestone sinkholes is a geologic hazard in coastal areas (mainly Brunswick, New Hanover, Pender, Onslow, Jones, Lenoir and Beaufort counties, North Carolina). Karst (sinkhole) features are widespread and impact transportation corridors and development. Knowing the geology beneath the ground can assist in determining where sinkholes may occur. Karst features were identified from color infrared aerial photographs, and supplemented with state government agency reports and field reconnaissance. Sinkholes in North Carolina come in many shapes and sizes. Many fill with water forming ponds or lakes, like around the town of Boiling Springs Lake and Sunny Point Military Ocean Terminal in Brunswick County, North Carolina. These features are distinct from the elliptical Carolina Bays which are much larger than sinkholes, and have an oval shape pointing in a northwest to southeast direction. Sinkholes may result in ground collapse and subsidence, and are a contributing factor in the rapid movement of contaminated groundwater. Sinkholes were responsible for the dewatering of Boiling Springs Lake, and for pavement subsidence such as along Interstate 40 near Wilmington. Sinkholes form naturally from limestone dissolution. Ground disturbing activity and changes in surface water and groundwater flow patterns can lead to the formation of new sinkholes. Notable sinkhole examples occur near Snow's Cut and Carolina Beach State Park (New Hanover County), Sunny Point Military Ocean Terminal and Boiling Springs (Brunswick County), and Catherine's Lake area (Onslow County). Digital geographic information system (GIS) data are intersected with critical facilities layers from HAZUS to assist local and state emergency preparedness. Additional investigations are underway.