Quantifying Shoreline Positions from Video Images at Upham Beach, Florida

摘要

Nourished material typically erodes from Upham Beach, Pinellas County,rnFlorida, within three years of placement. The June 1996 nourishment of Upham Beachrnwas concurrently monitored with standard beach profiles and video images from anrnArgus station. To evaluate the utility of video imaging as a supplement to postnourishmentrnmonitoring, thirty-two shoreline positions derived from both monitoringrnmethods were compared. The comparison resulted in a mean difference of less than 1 m,rnwhich is more than sufficient to resolve the magnitude of erosion at this site. Videornshoreline data display an interesting pattern of steady erosion during the first winter afterrnnourishment with some accretion during the summer of 1997, then, rapid episodic erosionrnduring the ’97-’98 El Ni?o winter. Shoreline positions reveal that erosion rates duringrnthe second winter after nourishment were twice those of the first winter, 0.4 versus 0.2rnm/day. Video images, with high spatial and temporal resolution shoreline positions,rnsuggest that the performance of 1996 nourished material on Upham Beach was not wellrncharacterized by uniform erosion.