Investigating local scour downstream of Piano key weir with Riprap

Piano key weirs (PKWs) represent a new form of labyrinth weirs. Regarding their high efficiency, it is essential to evaluate the scouring depth downstream, and provide solutions to reduce it. This study experimentally investigated the scour depth downstream of type B PKWs. Various parameters were implemented, including tailwater depth, flow rate, and riprap length. Riprap used in this study is comprised of synthetic materials that mitigate environmental risks and exhibit cost-efficiency. The result of the study is that the maximal scour depth is reduced by reducing the flow discharge and increasing the tailwater depth. The presence of Riprap at the downstream significantly reduces scouring. Moreover, as the length of Riprap increases, the maximum scour depth decreases. By a longer Riprap, the scour hole length expands while the scour index decreases.