Measurements of aeolian sediment transport in the vicinity of coastal dunes on Spiekeroog Island, Germany, and extrapolation to annual transport volume

Abstract. This work presents a field study measuring aeolian sediment transport and wind profiles across a dune, and provides an approximation of the annual volume of aeolian transport into the dune systems of the East Frisian island of Spiekeroog, using commonly available meteorological data. Aeolian sediment traps were positioned along a transect aligned with the general wind direction during the measurement, starting on the open beach and ending on the back site of a selected dune. Wind profiles were temporarily measured next to four aeolian traps. Using a recent version of an aeolian sediment transport model, the total annual aeolian sediment transport into the dune systems is approximated. Input variables for this model are the time series of shear velocity and surface moisture. These are derived from the wind velocity measured at a height of 10 m and the amount of precipitation in combination with potential evaporation calculated using radiation intensity. The results are compared to volume changes of the beach and dune systems, which are derived from geospatial data. Data from the field study shows, that sediment transport occurs even behind twenty metres of vegetation on top of a dune. Further, the study indicates that the impact of precipitation on aeolian transport reduction can be lower within vegetated areas on a dune compared to the open beach. The approximation of the total annual aeolian transported sediment surpasses the actual volume changes of the dune systems as expected, however this difference varies depending on the compared beach section almost by a factor of five.