Parapet Wall Effect on Piano Key Weir Efficiency

Abstract

The piano key weir is a cost-effective solution for rehabilitation as well as for new dam projects with a high level of constraints (e.g., limited space, high specific flood discharge, small reservoir level variation). Although the higher efficiency of the piano key weir compared with standard linear weirs has already been demonstrated, its optimal geometry is still poorly defined. To improve the design of the complex geometry of this structure, the use of parapet walls has been tested. They consist of vertical extensions placed over the weir crest. Following a former study of the influence of the weir height on its discharge capacity, this paper presents the results of an experimental campaign dedicated to investigating the effect of parapet walls to increase weir height while reducing bottom slopes and keeping the weir height constant. These results indicate the relative influences of the alveoli bottom slopes and of the weir height on the piano key weir release capacity. Comparisons with former experimental results are also provided.