Bedload transport and hydro-abrasive erosion at steep bedrock rivers and hydraulic structures

Sediment transport in glacier basins and rivers, and hence reservoir sedimentation tend to increase under the impact of climate change. The raise of bedload transport rates results in an increase of hydro-abrasive erosion leading to bedrock incision in rivers and wear at hydraulic structures. Mechanistic abrasion models are a helpful tool for both river and landscape evolution and hydroabrasion of hydraulic structures. Therefore, knowledge of the physical processes of turbulent flow characteristics, bedload particle motion, and hydroabrasion and their interrelations is needed. Ongoing research at VAW of ETH Zurich aims at improving the required knowledge to address hydroabrasion issues by means of laboratory and prototype experiments in supercritical flows over fixed smooth and transitionally rough beds. A physical model investigation revealed that particle trajectories on fixed planar beds are rather symmetric, flat and long compared to alluvial beds. By applying newly developed particle motion equations, an existing mechanistic abrasion model was adapted and calibrated for concrete and natural rock by means of prototype data. This advances abrasion prediction modelling and contributes to a better understanding of river bed and landscape evolution and to a sustainable design and operation of hydraulic structures facing severe hydro-abrasive erosion.