Quantifying rapid changes in coastal topography using modern mapping techniques and GIS

Innovative methodology based on a combination of Real Time Kinematic GPS (RTK-GPS), lidar, and open source GIS was developed to gain a better understanding of rapid changes in coastal topography. Improved spatial interpolation techniques were implemented to produce detailed topographic surfaces from lidar and RTK-GPS data. The methodology is demonstrated for two North Carolina areas: Jockey's Ridge State Park, and Bald Head Island. The Jockey's Ridge study quantifies recent dune movement and identifies areas of elevation loss and rapid horizontal migration that are threatening existing infrastructure. The Bald Head Island study examines preand post-nourishment beach evolution. The dynamics of beach topography, its geometric properties and estimates of eroded and deposited sand volumes were determined by combining lidar elevation data (1997-2000) with quarterly RTK-GPS measurements. Spatiotemporal analysis confirms the relative stability of the central “pivot point” beach section and reveals that the beach changes its shape from convex east of the pivot point, to concave to the west of it in 1997-98 and reversed shapes in year 2000. The pivot point also divides the beach into two sections that exhibit markedly different responses to nourishment. Although the entire length of nourished beach retreated, the analysis reveals that the western section lost all nourished sand offshore, whereas in the east section, significant sand volume was pushed up onto the beach, creating potential for recovery. Key Terms: digital elevation model , beach erosion , sand dune, lidar, Kinematic GPS, topographic analysis