An expansion device (1) for containing overflows of watercourses, floods and/or inundations and like phenomena, suitable for cooperating with further identical expansion devices for making barriers for containing overflows of watercourses, floods and/or inundations and like phenomena, comprises an enclosure (2) suitable for allowing the water permeability through said enclosure (2) and an expanding and absorbing material (3) inside said enclosure (2) and suitable for increasing in volume following the absorption of water. |