Hybrid Modelling Approach to Study Scour Potential at Chancy-Pougny Dam Stilling Basin Davide Wüthrich, Sabine Chamoun, Erik Bollaert, Giovanni De Cesare and Anton J. Schleiss 1 Introduction Chancy-Pougny Dam is a run-of-river dam located on Swiss–French border of the Rhône River downstream of Geneva. The dam is owned and operated by SFMCP (Société des Forces Motrices de Chancy-Pougny) and has a net head of about 10 m, with a powerhouse generating some 250 GWh of electricity per year. The main dam body contains 4 spillway gates for flood evacuation, each of them consisting of a flap gate at the crest and an orifice-type sliding gate at the base. Gates are numbered from the Swiss side towards the French side (Fig. 1). Furthermore, a fifth pass through the dam body contains a (non-equipped) ship lock on the French side. A picture of the hydropower plan is presented in Fig. 1, where both the dam and the powerhouse can be observed. Since the dam’s construction in 1920–1925, the unlined stilling basin down- stream of the dam has been subjected to progressive scour of the vulnerable marls and sandstones. Hence, a hybrid modelling was performed to study the scour potential in the unprotected stilling basin and to determine adequate solutions to D. Wüthrich  S. Chamoun  G. De Cesare (&)  A. J. Schleiss EPFL, LCH, Station 18, 1015 Lausanne, Switzerland e-mail: giovanni.decesare@epfl.ch D. Wüthrich e-mail: davide.wuthrich@epfl.ch S. Chamoun e-mail: sabine.chamoun@epfl.ch A. J. Schleiss e-mail: anton.schleiss@epfl.ch E. Bollaert AquaVision Engineering, Chemin des Champs-Courbes 1, 1024 Ecublens, Switzerland e-mail: erik.bollaert@aquavision-eng.ch © Springer Nature Singapore Pte Ltd. 2018 P. Gourbesville et al. (eds.), Advances in Hydroinformatics, Springer Water, https://doi.org/10.1007/978-981-10-7218-5_62 869