Hydro-abrasion processes and modelling at hydraulic structures and steep bedrock rivers: 2. Hydro-abrasion model development and application

• An existing mechanistic saltation hydro-abrasion model is enhanced with new formulae for particle dynamics, cover effects, hardness, and saltation probability. • The enhanced model holistically incorporates new factors of particle hardness, bed cover and low aspect ratio. • Calibration with laboratory and field data from three Swiss Sediment Bypass Tunnels yields a constant hydro-abrasion coefficient k v = 4.8 ± 2.2 × 10 4 , with significantly reduced scatter compared to earlier studies. • The enhanced model accurately predicts abrasion and supports the upscaling of laboratory results to prototype conditions. • Findings offer practical implications for the selection of abrasion-resistant invert lining for hydraulic structures prone to hydro-abrasion and contribute to understanding landscape evolution under sediment-laden flows Hydro-abrasion is a process of wear resulting from the mechanical stress exerted by impacting particles in the flow on a riverbed or banks or on the invert of hydraulic structures. Hydro-abrasion models represent the mechanics of invert abrasion by bed load particles and allow to predict hydro-abrasion rates. The present study deals with the enhancement of the existing mechanistic saltation hydro-abrasion model by incorporating new equations for particle velocity, hop length, an exponential cover effect term, and two additional important terms accounting for particle hardness and saltation probability, respectively. We particularly focus on the effects of particle and bed lining material hardness, bed cover, and low aspect ratio on hydro-abrasion, which were not holistically investigated in previous studies. The non-dimensional hydro-abrasion coefficient ​ k v ​ (also known as the rock resistance coefficient) in the enhanced model was calibrated using both experimental laboratory data and field measurements obtained from three Swiss Sediment Bypass Tunnels as part of our research project. A constant value of k v = 4.8 ± 2.2 × 10 4 was obtained for a range of different materials with less scattering compared to the coefficients reported in previous studies. The enhanced model demonstrated a good performance when validated with independent data from laboratory and field studies, indicating that the laboratory results can be upscaled to prototype conditions.