Measuring Clast Movement on Gravel Beaches

Abstract

Native tracer cobbles were tracked on a mixed sand and gravel beach at three temporal scales. Passive Integrated Transponder tags were inserted in 400 cobbles and tracked at monthly intervals over 130 days; tags were inserted in a further 200 cobbles and tracked on days 1, 2, 4, 6 and 16. Despite similar incident wave conditions, opposing directions of dominant sediment transport occurred in the two tag tracer experiments. A new technique was developed using painted cobbles and drone video capture to provide a third set of measurements on 175 tracer cobbles at the scale of individual swash events. Large differences were quantified between net and gross sediment transport rates. Collectively these data provide rare direct comparable measurements of the dynamic and variable nature of sediment transport on gravel beaches across different temporal scales.