Labyrinth weirs are normally built to increase the total effective crest length for a given spillway width. They can be used to increase the discharge capacity for a given head or to decrease the head for a given discharge. As their application is sometimes difficult in rehabilitation projects due to inappropriate supporting conditions, a new concept of labyrinth spillways was mooted by Lemperiere et al. with a new shape, called Piano Key Weir. This innovative alternative of labyrinth spillway provides an increase in the stability of the structure which can be placed on the top of most existing or new gravity dams, unlike traditional labyrinth weirs. This paper focuses on the experimental results and physical modelling tests of the evacuation system of Sawara Kuddu Hydro Electric Project 110 MW located in Lower Himalayan mountain ranges of India with the Piano Key Weir and the energy dissipation structure. The physical modelling has been carried out at the River Engineering Laboratory, Water Resources Development and Management, Indian Institute of technology, Roorkee, India in the framework of the rehabilitation project. © 2011 Taylor & Francis Group, London.