Sand transport by wind through foredune blowouts: implications for coastal dune evolution

Authors: Irene Delgado-Fernandez*, , Nicholas O'Keeffe, Edge Hill University
Topics: Coastal and Marine
Keywords: blowouts, beach-dune dynamics, secondary airflows, coastal dunes
Session Type: Virtual Paper
Day: 4/9/2021
Start / End Time: 8:00 AM / 9:15 AM
Room: Virtual 45
Presentation File: No File Uploaded

Coastal blowouts are acknowledged as highly effective transport pathways on dune-fringed coastlines. Their ability to modify airflow has been extensively researched, with numerous 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 study explores 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). The study focuses on the Sefton dunes, northwest England. Here, the availability of long-term sets of aerial photography and high-resolution LiDAR makes it possible to quantify beach-dune sediment budgets, and changes to blowouts locations and structure. High-frequency measures of wind and transport during a short-term experiment at a foredune blowout at the site allow analyses of complex aeolian processes at the beach-dune interface and within the blowout throat. Results permit exploration of links between human recreation on foredunes, the development of trough blowouts and coupled parabolic dune systems, and the consequences for dune field evolution.

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