Modification of offshore wind flow and aeolian sand transport by artificial foredunes

Abstract

Airflow dynamics and aeolian sand transport under offshore wind conditions have primarily been examined over relatively large coastal dunes, where dune morphology significantly alters flow structure and sediment pathways. In contrast, the role of smaller-scale, anthropogenically constructed coastal sand dunes, remains relatively understudied. This study investigates airflow patterns and sand transport over a low (<2.5 m) artificial foredune in Leucate (South of France), exposed to dominant offshore winds. A high resolution network of anemometers and aeolian sand traps was deployed along a cross-shore transect during four field campaigns. Results indicate that the direction of incident offshore winds generated distinct patterns of airflow and sediment transport from the dune's lee slope to the beach. When wind approached within 20° of crest-normal, flow separation occurred on the lee side, with wind speeds reduced to 10–20 % of crest values. For angles >20°, flow remained attached but deviated alongshore, with wind speeds reaching 35–50 % of crest values at the dune seaward toe. Wind velocity consistently increased seaward, enhancing sand transport toward the berm, with maximum transport rates exceeding 300 kg/m/h. This seaward-directed transport contributed to a negative sediment budget under persistent offshore wind dynamics. These findings highlight the capacity of small, artificial dunes to modify offshore wind dynamics and sediment pathways, with implications for dune management and coastal sediment budgets.