Automatic wicket for a hydraulic structure

An automatic flashboard for a hydraulic structure (11) such as a weir, or a spillway on a dam or on a protective embankment, the flashboard comprising:

• (A) a watertight or substantially watertight wall (12) installed on said structure (11) so as to be capable of passing from an erect, first position for retaining a mass of water to a lowered, second position in which said wall (12) allows water to pass essentially without obstruction, and
• (B) at least one elongate retaining element (13;
• 13′) for holding said wall (12) in its first position against a horizontal thrust (P1) exerted by the mass of water (25), said elongate retaining element (13;
• 13′) being connected to said wall (12) via a connection (14) and being subjected in operation, under thrust from the water, to a longitudinal force (T), extending between said wall (12) and a reaction point remote from said wall (12) and counterbalancing said longitudinal force, and being connected to the reaction point via a connection (15, 15′) that can be eliminated without human intervention when the water reaches a certain level, such that said wall (12) passes automatically into its second position,
• said flashboard being characterized in that it further comprises:
• (C) a massive element (16;
• 16′) movably mounted on said structure (11) and coupled to said mass of water so as to be in a position of stable equilibrium so long as the water remains below a predetermined level (N) and so as to pass into an unstable state and be displaced when the water reaches said predetermined level, said connection (15) being eliminated by the displacement of said massive element (16, 16′).