Using topographic lidar data to delineate the North Carolina Shoreline

In North Carolina, shoreline change rates are an important component of the state's coastal management program. To enhance methods of measuring shoreline change, the NC Division of Coastal Management (DCM) is considering using mean high water (MHW) shorelines extracted from lidar data together with traditional wet/dry shorelines digitized from aerial photography. To test their compatibility, a wet/dry line and MHW shoreline derived from a concurrent 2004 oceanfront photography and lidar dataset were compared along a distance of 244 km. Results show that the MHW shoreline was seaward of the wet/dry shoreline by 2.82 m on average, and that this offset biased shoreline change rates by an average of 0.05 m/yr. The offset was greatest on low-sloping beaches experiencing higher water levels at the time of photography, but overall was small enough to suggest that the MHW shoreline can be a reliable substitute for the wet/dry shoreline.