The influence of hydrodynamic boundary conditions on characteristics, migration, and associated sand transport of sand dunes in a tidal environment

Abstract

Large parts of the tidal estuary of river Elbe (Germany) are characterized by regular patterns of sand dunes. They evolve due to complex sand transport mechanisms and show multi-faceted migration patterns, which are influenced by hydrodynamic boundary conditions such as runoff and tidal forces. This study aims at increasing the understanding of the way hydrodynamic boundary conditions influence dune behavior. This is the basis of an effective sediment management as well as an important requirement for planning offshore structures. From a unique data set of up to six annual bathymetrical multibeam soundings between 1995 and 2010, bedform characteristics and migration rates were processed and analyzed with a set of automated methods. The influence of river runoff, water levels, current velocities, tidal range, and river depth on characteristics and migration were tested statistically. The results show that migration is mainly dominated by the incoming flood tide while rates and directions depend on the amount of runoff originating from the inland catchment.