Flood guiding method and plant

A guidance system for protecting a specific zone as a safety zone against flood water while protecting landscapes near the specific zone from deteriorization. According to the described flood water guidance system, a guidance plate (5, 5, . . . ) is positioned under underground in the vicinity (S'1, S'2, S''1) of an upstream side of a specific zone (SI, S2) containing property to be protected and where it is anticipated that flood water will flow, and when flood water is generated, or when there is a possibility that flood water may be generated, the guidance plate (5, 5, . . . ) is raised to a predetermined height above the surface of the earth, in order that a specific zone (S1, S2) is protected as a safety zone by diverting the flood water from the specific zone (S1, S2) by way of the raised guidance plate (5, 5, . . . ), and by guiding the flood water to a retarding basin, a drainage canal, and the like.