Provided is a flood control system including a plurality of power generation facilities and a plurality of cavitation prevention hole, which are connected to an inverted siphon waterway, a separate artificial construction, so as to manage river flow from a starting point of the river to an end point before entering the sea. The power generation facility includes a first cavitation prevention holeformed in an upper air layer of an intake water intake reservoir; a hydraulic turbine installed at a downstream of a hydraulic pressure pipe being connected to the cavitation prevention hole to generate electric power; and a second cavitation prevention hole formed in a discharge water reservoir located in the vicinity of the hydraulic turbine.