An experimental study carried out on a movable bed physical model at the Laboratory for Applied Hydraulics of HEPIA yielded an innovative solution to replace a fish pass suffering from clogging on the Arve River in Geneva. Fish migration in the Vessy meander is altered by a 220 m long, 3.5 m high spillway conveying a part of the river discharge to a low-head hydraulic power station. Since the Suisse Federal Law on Fishing (RS 923.0) requires from all power plant operators to guarantee a free fish migration the Service Industriel de Genève (SIG) is obliged to replace the inoperative fish pass. The main achievements of the investigations are a) calibration of the physical model to the current hydro- and morphodynamics; b) identification of the appropriate location of the fish entrance and the water intake of the future fish pass; c) hydraulic analyses of new structures; d) proposal of a sustainable and ecological solution. The analyses pointed out that a bypass river would gather the largest number of benefits. A concrete fish pass would suffer from clogging. A riprap ramp, although less exposed to clogging, would offer favourable hydraulic conditions only up to medium discharges of the Arve River. The bypass river would run on Arve’s right overbank. Bed load is deflected by a groin implemented in the Arve upstream from the new water intake, protecting the latter from clogging. The new fish pass should offer optimal flow and ecological conditions for all fish species and can therefore be constructed.