Remobilization and transport of particles in the nearshore zone of Lake Constance, Germany

Session: Physical Processes in Lakes (3)

Hilmar Hofmann, University of Konstanz, Limnological Institute, [email protected]

Abstract

Many lake shores experience erosion due to modifications in shore morphology, e.g. harbors and piers, long-term changes in water level and storm events. It is of upmost importance to understand the governing processes of erosion, e.g. the interaction between the nearshore hydrodynamics, sediment remobilization, and transport. Sediment dynamics in the nearshore zone of lakes are strongly affected by the characteristics of the surface wave field, the basin-scale background currents, the particle properties of the upper sediment layer and the water level dynamics. Nearshore hydrodynamics as well as sediment dynamics and budget were studied by short- and long-term measurements in Alpine Lake Constance. These measurements were combined with different numerical experiments using a wave, wave propagation and sediment transport model. Only during strong onshore wind events significant remobilization and transport of particles could be observed. The background current field was dominated by alongshore-directed velocities especially in the shallow nearshore zone, where significant net sediment transport occurred. The pattern of the resultant background current field is seasonally varying and is highly affected by the interplay between the direction of the large-scale currents, the direction of the surface wave field, and morphological features in the nearshore zone.