Dune behavior and aeolian transport on decadal timescales

Abstract

Dunes provide protection for low lying hinterland against flooding due to storms. Due to the dynamic nature of dunes, safety levels provided vary in time. This paper aims to gain insight in how dune building processes govern dune behavior on the yearly to decadal timescale. Dunes grow mainly due to aeolian transport.Most sediment transport formulations suggest that wind velocity is the most important governing parameter for aeolian dune growth. However, in several coastal studies, wind-driven sediment transport has been shown to reach limiting conditions regardless of the wind velocity. Factors that limit the wind-driven sediment transport, such as sediment properties, moisture and beach geometry, can be more important than the wind velocity.The Dutch JARKUS dataset is used to analyze yearly to decadal dune behavior where dune volume changes are taken as a measurable parameter of dune behavior. Measurements of dune volume changes over these timescales mainly show a positive linear trend. Therefore a constant dune growth could be assumed for these specific profiles, which simplifies predictive possibilities. However, the magnitude of the linear dune behavior varies in space (alongshore). It is aimed to find spatial and temporal variations in dune behavior and how these correlate with wind conditions and beach slope. The dune volume changes are found to depend on beach slope which is a transport limiting parameter but no relation between dune behavior and wind forcing is found on the yearly to decadal timescale. Annually averaged erosion volumes as a result of extreme marine events are found to be of similar order as the aeolian growth. In future modeling of decadal dune behavior, we suggest that the variability of transport limiting parameters is of interest rather than time varying forcing conditions such as varying wind speeds and drift potentials.