AEOLIAN SEDIMENT TRANSPORT THROUGH FOREDUNE BLOWOUTS: IMPLICATIONS FOR BEACH-DUNE INTERACTION AND DUNE FIELD EVOLUTION (Invited Presentation)

Coastal blowouts are acknowledged as highly effective transport pathways on dune-fringed coastlines. Their ability to modify airflow has been extensively researched, with a growing number of studies exploring their role in allowing beach sediment to by-pass foredunes and travel landwards directly into the dune field. However, less attention has been paid to their general role in coastal dynamics. As the evolution of sandy coastlines is governed by sediment exchanges between sub-units of the cross-shore profile (nearshore, beach, and dune), blowouts located at the beach-dune interface may play a significant role in coastline change through enhancing the landward transfer of sediment into the dune field. This can modify sediment budgets locally, with implications for coastal dune response to both marine and wind events.

This talk will explore the ability of coastal blowout topography to modify airflow and aeolian sediment transport at the short scale (hours-days), and the implications of this for coastline evolution at the medium term (years-decades). Examples will be drawn from locations in the UK and Spain, where synchronous high-frequency measurements of airflow and sediment exchange from the beach into the dune field provide new insights into transport pathways, the role of wind direction, and complex relations between turbulence and transport intensity. At the medium term, a combination of aerial photography and DEMs of Difference (DoD) enables quantification of morphological and volumetric changes along several sites, and understanding of the links between these and coastal change. Results have implications for management plans aiming at decreasing coastal vulnerability and the risk of coastal erosion.