Direct observations of bedform migration driven by turbidity currents in a lacustrine channel

Abstract

Turbidity currents, gravity-driven sediment-laden flows, govern material transport and shape underwater landscapes across diverse environments. While extensively studied in marine settings, their dynamics in freshwater systems remain underexplored. We present multi-temporal, multi-scale observations from the Aare Delta of Lake Brienz (Switzerland), combining Acoustic Doppler Current Profiler measurements with high-resolution repeated bathymetric surveys to capture turbidity currents and resulting morphological changes. A single turbidity current reached near-bed velocities of 0.65 m/s and induced upslope migration of a cyclic step by at least 4 m within minutes. Characterisation of overall bedform migration across the channel network over five years highlights the cumulative imprint of turbidity currents and frames these short-term changes within the broader context of channel reworking. Together, our results show striking similarities in overall flow structure, bedform morphologies, and dynamics between freshwater and marine systems, underscoring the value of lacustrine settings as accessible, scaled-down environments for advancing turbidity current research.