Author(s): Nicolas Duparc; Anthony Garcia; Nicolas Andreini; Davide Ceresetti

Linked Author(s): Davide Ceresetti

Keywords: Fishway; Sediment flushing; Self -Scouring; Physical Model; Scale similarity

Abstract: The reopening of the Drize River and its reconnection to the Arve River requires a fishway capable of enabling upstream fish migration while remaining operational under the highly variable sediment loads of the Arve River. To address potential clogging risks and ensure long-term functionality, we implemented a multi-scale methodology combining (i) a 1:1 in -situ prototype to characterise real sediment inputs, (ii) numerical modelling to assess hydraulic performance, and (iii) a 1:3 physical model to investigate coupled hydraulics and sediment transport. Sediments collected in the field were analysed for grain -size distribution and cohesive fraction; the mixture used in the 1:3 model was slightly modified by removing the largest particles to satisfy particle Reynolds and Shields similarity, while maintaining the natural cohesive fraction, which is critical for clearing behaviour. The 1:3 model is then used to test the effectiveness of a jet -based flushing system designed to enhance self-scouring capacity. Various jet configurations, discharge scenarios, and geometric adaptations are evaluated to determine whether such a system can efficiently mobilise and evacuate deposited sediments while preserving favourable conditions for fish passage. This integrated multi-scale approach provides a robust basis for designing a self-clearing fishway capable of functioning more than 300 days per year as requested by the Federal Office for the Environment.

DOI: https://doi.org/10.64697/iahr.proc.ise2026.abs.211

Year: 2026