Detecting Seasonal Variations in Embryo Dune Morphology Using a Terrestrial Laser Scanner

ABSTRACT Montreuil, A-L., Bullard, J.E., Chandler, J.H., 2013. Detecting seasonal variations in embryo dune morphology using a terrestrial laser scanner. In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.) Coastal embryo dunes are rarely the focus of research efforts despite the fact that they are often precursors to the development of established coastal dune fields. The aim of this paper is to quantify morphological changes within an embryo dune field using a terrestrial laser scanner (TLS), with particular emphasis on determining how the number, height and orientation of dunes changes from season to season in relation to external forcing factors. The study site was located on the upper (> MHWS) section of a macrotidal beach on the north Lincolnshire coast (UK) where the wind regime includes both onshore and offshore components. Dune morphology was monitored approximately every three months over a period of 16 months (July 2009– October 2010) using TLS. The volume of sand within the embryo dune field ranged from a minimum of 12,622.54 m3 in January 2010 to a maximum of 13,263.17 m3 in June 2010. The majority of volume gain was a result of seaward accretion in response to onshore aeolian sediment supply as opposed to either a gain in height or an expansion of the dune field in an alongshore direction. Sediment volume was reduced in the embryo dune field as a result of two severe storm surge events that occurred during the winter months. The storm surges caused elongated areas of erosion between dunes, aligned with the dominant wind direction. Between October 2009 and January 2010 the volume of the dunes decreased by 315.49 m3 corresponding to a volumetric ratio of sand thickness of −0.026 m month−1. However, subsequent surveys show that the dunes then progressively recovered. This research demonstrates the potential of high resolution terrestrial laser scanning for identifying small-scale morphological changes in coastal dune fields, essential for relating detected change to evolutionary processes.

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