Abstract Energy dissipation is one of the important issues in piano key weirs (PKWs). Excessive energy at weir's toe can cause scouring. In previous studies, arced (APKWs) has not been investigated. this experimental study, effect weir height as well and arrangement baffles located on outlet slope amount dissipated were examined trapezoidal (TPKWs) APKWs. Experiments performed models with two t...