High-resolution analysis of shoreline change and application of balloon-based aerial photography, Albemarle-Pamlico Estuarine System, North Carolina, USA
Limnol. Oceanogr. Methods 11:151-160 (2013) | DOI: 10.4319/lom.2013.11.151
ABSTRACT: Previous studies of shorelines have relied on satellite imagery or airplane-based aerial photography, which can be costly, of limited availability, and of restricted resolution. These factors limit the usefulness of such imagery for detailed shoreline-change measurements that require frequent observations with high spatial accuracy. Easily deployed balloon-based photography systems can provide high spatial and temporal resolution images at relatively low cost. This study used an Aerostat balloon photography system along with real-time kinematic (RTK) GPS to observe subannual changes in the shoreline position of the Albemarle-Pamlico Estuarine System (APES), North Carolina, USA. The fine (0.03 m-pixel) resolution of Aerostat images is ideal for mapping shoreline areas although limited in spatial extent. Features digitized from these images compare well in position (0.5 ± 0.5 m) and accuracy (± 0.4 m) to in situ RTK-GPS surveys. The balloon system is best used concurrently with RTK-GPS surveys to obtain the highest possible georectification accuracy. Results demonstrate that this method is well suited to high-accuracy analysis of shoreline positions over short timescales (annual to subannual), and that the balloon images provide a valuable spatial context for any measured changes. Preliminary analysis of shoreline change across the APES highlights great spatial and temporal complexity. Annualized rates of change reached >30 m/y, but average net changes were modest for survey periods (-0.5 m to 0.04 m). Tropical systems (e.g., Hurricane Earl) can be key drivers of the observed shoreline response, and the associated sediment dynamics likely have important ecological (e.g., submerged-aquatic-vegetation and water quality) ramifications.