This preparedness guide by the Nat. Weather Service (NWS) explains flood-related hazards and suggests lifesaving actions you can take. With this info. you can recognize a flood potential, develop a plan, and be ready when threatening weather approaches. Your safety is up to you! In the long term, floods kill more people in the U.S. than other types of severe weather. Floods can roll boulders the size of cars, tear out trees, destroy buildings and bridges, and pose a significant threat to human lives. Once a river reaches flood stage, the flood severity categories used by the NWS include minor flooding, moderate flooding, and major flooding. Each category has a definition based on property damage and public threat. Color illustrations.