Monitoring and Assessment of Rapid Changes in Coastal Topography Using LIDAR, Real-Time Kinematic GPS, and Open-Source GIS

Seventh International Conference on Remote Sensing for Marine and Coastal Environments

Helena Mitasova and Thomas G. Drake
Department of Marine, Earth, and Atmospheric Sciences
North Carolina State University, Raleigh, NC 27695
and
Russell S. Harmon
Army Research Office, Army Research Laboratory, Research Triangle Park, NC 27709
Dynamic coastal topography poses significant land management challenges. Cost-effective monitoring and spatial analysis are needed to provide fundamental insights into coastal landscape dynamics and support sustainable development. An innovative approach for assessing short-term coastal topographic change has been developed by combining LIDAR, Digital orthophotography (IR-DOQQ), and RTK-GPS data, supported by Open-Source-GIS GRASS5 tools for spatial interpolation, topographic analysis and visualization.

At Jockey's Ridge State Park, the 1998 IR-DOQQ, 1999 LIDAR, and 2002 RTK-GPS data were integrated to determine the extent and rate of horizontal and vertical movement of this large coastal sand dune. Simultaneous spatial interpolation and terrain geometry analysis from LIDAR data was performed using Regularized Spline with Tension, with profile curvature used to precisely identify dune crests. Overall, vertical change indicates dune flattening, with peak elevation falling 2.6m between 1999 and 2002.The fastest-moving dune crests have a displacement rate of 20m/yr, posing a serious threat to developed areas adjacent to the park.

Before and after re-nourishment dynamics of shoreline sediment transport along Bald Head Island was also examined. The evolution of beach topography, including its geometric properties and estimates of eroded and deposited sand volumes, was determined by combining LIDAR elevation data (1997-2001) with monthly RTK-GPS shoreline and beach profile measurements. The Southern Beach eroded 445,000 and deposited 225,000 cubic meters of sand with the western section eroding at 10m annual rate, slope increasing from 6deg to 20deg and profile curvature changing from concave to convex. The RTK-GPS data indicate the same spatial pattern of erosion and deposition after re-nourishment with fast eroding western section, more stable center and growing eastern tip of the beach.
Supported by the National Research Council and the Terrestrial Sciences Program of the Army Research Office

Comments: Helena Mitasova