Flood infrastructure: Localized scour at piano key weirs

Historic growth in the US coupled with observed hydrologic changes have created an increased demand for sustainable flood protection. One approach to passing floodwaters is nonlinear weirs such as labyrinth and Piano Key weirs (PK weirs). Although they are being designed in greater frequency, one area lacking in information or design guidance is the prediction of local scour at these weirs. Without proper protection, downstream local scour can compromise the weirs' foundation. Therefore, a large-scale laboratory study has been undertaken to investigate the effect of different lengths of downstream aprons on the scour mechanism at the foundation of a PK weir. This paper presents a preliminary analysis of equilibrium scour morphology under different flow conditions and with non-cohesive bed material. Instrumentation included 3D cameras and ultrasonic sensors to capture scour features and measure dynamic water surface elevations, respectively.