Using LIDAR to monitor a beach nourishment project at Wrightsville Beach, North Carolina, USA

Abstract

With beach nourishment widely used today to combat shoreline erosion, it is desirable to monitor the postnourishment shoreline to evaluate the projects' success. Implementing a monitoring program is difficult because of time and personnel requirements. Remotely sensed elevation data, in particular that derived from airborne light-detection and ranging (LIDAR) sensors, could be used because of its extensive coverage. In 1998, a beach-fill project was carried out at Wrightsville Beach, North Carolina, and coincidentally LIDAR data were collected annually in this location from 1997 to 2000. This project uses the LIDAR data to identify beach and dune zones and to compute volumetric changes for each zone. Spatial variations are analyzed by examining shoreline segments, in which beach and dune volumes are determined for the different surveys. Spatial and temporal changes in both the beach and dune zones are monitored following the initial fill project. The passage of hurricanes Bonnie and Floyd in the fall of 1998 and 1999, respectively, provided an opportunity to evaluate how the nourishment project was affected by major storms. About two thirds of the initial fill material was removed from the subaerial part of the beach in the first year, probably mostly as a result of the hurricanes. The highest rates of beach sediment loss occurred in the nourishment zones. There was some recovery in the following years. The dune system also changed, both losing and adding sediment in different time periods. The influence of human manipulation of the dune is evident in the cross-shore profiles and the volumetric data. There is little evidence that the fill material moved alongshore to nourish subaerial areas adjacent to nourished zone. Although the nourished beach undoubtedly provided a buffer against the storm waves, poststorm beach recovery was not evident 2 years after the storms, making the long-term success of this project questionable.