What are the different causes of flooding? How do we measure and communicate the severity of an earthquake? What factors influence the likelihood of wildfires? What risks do nuclear power plants pose to nearby communities? The following three chapters address these and myriad other questions by exploring a wide range of natural and human-made hazards facing the United States, delving into their causes, characteristics, classifications, and describing notable historic events experienced in the United States and around the world.
Before we can take action to reduce vulnerability to hazards, it is important to fully understand common types of hazards and be able to anticipate the damage resulting from each. Chapter 3 discusses natural hazards connected with Earth’s water system, including hurricanes, sea level rise, drought, tornadoes, severe winter weather, extreme heat, and wildfires. Chapter 4 focuses on geological hazards such as earthquakes, tsunamis, volcanoes, landslides, and coastal erosion. In Chapter 5, we turn to human-made hazards, both technological accidents such as chemical spills, as well as threats that are intentional and malicious in nature.
Every community has a slightly different hazard profile, meaning the likelihood and potential severity of these hazards are not uniform from one community to the next. Sea level rise will continue to have profound impacts on much of southern Florida, while residents of a landlocked state like Oklahoma are more concerned with hazards such as tornados, flood, and drought. It is also important to consider how and why the hazard profile in a given community might shift over time. For example, changes in development patterns can increase the quantity of stormwater runoff resulting from a thunderstorm. Some areas that have typically had sufficient freshwater over the past century may have to use water more sparingly in the future as agriculture, energy, and industry compete for waning water supplies. The following section discusses these changes, due to both climate change and human activity, and provides the foundation for communities to prepare for and mitigate risks from natural and humanmade hazards.
In addition to the causes and consequences of hazards, it is important to have uniform ways of communicating about hazards. How would an emergency manager in coastal Virginia differentiate between a minor tropical storm and a catastrophic hurricane when communicating an evacuation order? How do developers and builders decide how high the foundation of a new house should be to reduce the likelihood of flooding? The following section outlines systems that are commonly used to classify and describe hazards. In addition to providing useful information for citizens and those responsible for responding to an event, widely used methods of categorizing the likelihood or intensity of hazard events are essential for designing policy and prioritizing mitigation actions that address the most significant risks to a community.