Definition of an Erosion Law for Sediments of the Saône River, France

The erosion of riverbeds and banks in navigable channels controls the stability of the channel, the flow of sediment, and the maintenance of navigation depth. Understanding the erosion dynamics of natural sediments is crucial for predicting morphodynamical changes due to human-induced hydraulic influences.

This research examines the erosion characteristics of transitional fine to medium sand sediments from the Saône River (France), with the goal of establishing an empirical erosion law that connects hydraulic shear to sediment transport in these materials. Granulometric analyses revealed well sorted medium sand (D₅₀ ≈ 140 –160 μm), suggesting weak cohesion yet hydraulically mobile beds. Flume experiments performed under regulated flow conditions demonstrated a gradual onset of erosion within a flow rate range of 26–47 l/s, indicating that incipient motion takes place along a continuum rather than at a specific critical threshold. Time-dependent experiments indicated an initial period of quick detachment succeeded by a decrease in erosion rate, influenced by surface armoring and a depletion of the easily entrainable fraction. Dimensionless transport data were fitted using the Meyer-Peter and Müller (1948) and Van Rijn (1984) expressed respectively as Φ = 140.3(θ − 0.07)^4.43 and Φ =0.00153 d_∗^-0.3(θ/0.07 - 1)^4.43 with R² ≈ 0.74. The steep exponents highlight the nonlinear sensitivity of transport to excess shear stress, characteristic of transitional sediments. The derived relationships provide a quantitative foundation for predicting ship-induced erosion and sediment mobilization in navigable river systems.

This research was funded in whole or in part by the Agence Nationale de la Recherche (ANR) under project ANR-23-CE51-0032-01