& The so-called Hinged Flap Gate is introduced. This gate is able to control automatically the upstream water elevation for free gate¯ow. Based on laboratory observations, the hydrodynamic pressure distribution on hinged gates was determined.Application of the equation of moments gives two conditions to be satis®ed: the moment required by the counterweight, and the angle of the counterweight relative to the normal to the gate at the pivot. The performance of the device is described. Gate vibrations are demonstrated to be absent. The main application of the Hinged Flap Gate is in sewers and irrigation channels for controlling relatively small discharges. A historical note on the development of regulating gates is also given to show that the hydraulically controlled Hinged Flap Gate is a novel suggestion.