• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.9 no.3
• /
• pp.155-164
• /
• 1997

A comprehensive and systematic field monitoring program was initiated since October 1989, in order to investigate the temporal and spatial variation of shoreline position at northern part of Pea Island, North Carolina. Aerial photographs were taken every two months on the shoreline extending from the US Coast Guard Station at the northern end of Pea Island to a point 6 miles to the south. Aerial photographs taken were digitized initially to obtain the shoreline position data. in which a wet-dry line visible on the beach was used to identify the position of shoreline. Since the wet-dry line does not represent the “true" shoreline .position but includes the errors due to the variations of wave run-up heights and tidal elevations at the time the photos taken, it is required to eliminate the tide and wave runup effects from the initially digitized shoreline .position data. Runup heights on the beach and tidal elevations at the time the aerial photographs taken were estimated using tide data collected at the end of the FRF pier and wave data measured from wave-rider gage installed at 4 km offshore, respectively A runup formula by Hunt (1957) was used to compute the run-up heights on the beach from the given deepwater wave conditions. With shoreline position data corrected for .wave runup and tide, both spatial and temporal variations of the shoreline positions for the monitoring shoreline were analyzed by examining local differences in shoreline movement and their time dependent variability. Six years data of one-mile-average shoreline indicated that there was an apparent seasonal variation of shoreline, that is, progradation of shoreline at summer (August) and recession at winter (February) at Pea Island. which was unclear with the uncorrected shoreline position data. Determination of shoreline position from aerial photograph, without regard to the effects of wave runup and tide, can lead to mis-interpretation for the temporal and spatial variation of shoreline changes.nges.