Measurements and modeling of aeolian sand transport on dynamic cobble berm revetments

Abstract

Dynamic cobble berm revetments are a nature-based adaptation solution aimed at preventing or slowing coastal erosion. Dynamic cobble berm revetments mimic natural composite beaches that consist of a low-sloping sandy beach backed by a steeper cobble slope. During high wind conditions, wind can blow sand from the sandy beach into the cobble berm. Subsequent infilling of a dynamic revetment by aeolian (wind-driven) sand transport is hypothesized to affect its morphological development and performance, e.g. by reducing wave infiltration and increasing overtopping. However, aeolian sand transport on dynamic cobble berm revetments has not yet been measured or simulated with numerical models. Here, we use event-based field measurements to show that aeolian sediment transport on dynamic revetments is dependent on the wind speed and moisture content on the beach, and that dynamic revetments can trap 93–100 % of the aeolian sand transport from the beach. Additionally, we adapt a numerical aeolian sediment transport model (AeoLiS) to replicate the physical processes, such as sediment trapping, that alter sand transport on a dynamic revetment. As a result, the modified model reproduces the timing and spatial patterns of measured aeolian transport and the sand trapping efficiency of dynamic revetments. A simulation of sand infilling on a dynamic revetment shows how sand trapping is reduced once a dynamic revetment is filled with sand. The modified model considers wind-driven sand infilling and provides a pathway for considering the combined effect of marine and aeolian processes (i.e., by coupling with a hydrodynamic model) in dynamic revetment design.