Intertidal beach level estimation from video images

Abstract

Since 1992 nearshore hydrodynamics and coastal morphology have been studied from ARGUS video images, collected every hour at eight beach locations worldwide. Identification of the waterline from these images would enable us to obtain an impression of the intertidal beach bathymetry, and hence to monitor intertidal beach morphodynamics. In this way structural shoreline retreat or advance can be monitored, which is of great importance to Coastal Zone Managers. Unfortunately, the waterline cannot always be identified easily from 12 minutes time averaged images. In this study a new technique has been developed, which estimates the location of the waterline froll both time averaged and standard deviation images. When considering the spatial correlation pattern between the two signals, a characteristic feature shows up around the waterline. In this way the position of the waterline can be determined with an accuracy of about 15 cm in vertical sense, and 5 10 m in the horizontal plane, values who satisfy well given the methods of field survey and comparec to traditional methods.