Reports from the scenes of natural disasters—raging wildfires, unrelenting floods, violent ground shaking, and devastating tornadoes and hurricanes—fill our news feeds every day. These hazards cause deep disruptions to the health of humans and ecosystems and threaten the safety and integrity of buildings and infrastructure.
The severity and frequency of some natural hazards are increasing with climate change. But humans are contributing to the problem in another way: building structures in hazard zones. In a new study that aims to determine the role development plays in the overall risk of natural hazards, Iglesias et al. looked at how development in the contiguous United States has influenced natural hazard risks to structures. They looked at the changes in the number and distribution of buildings between 1945 and 2015 and how development changed people’s exposure to natural hazards.
The researchers first made a hazard map of the United States that included earthquake, wildfire, hurricane, tornado, and floods with data from federal agencies and Fathom (for flood data). Then they identified “hazard hot spots” that correspond to areas where the frequency or intensity of an event falls in the top 10%. Although hazards tend to congregate in certain areas—hurricane risk is high around the Gulf Coast, for example—there can be some spillover into other areas.
When scientists or policymakers look at exposure risk to natural hazards, population density is often a key factor—for instance, the number of people who would be affected by a tornado. But in this study, the researchers focused more on the presence of structures, information they obtained from Zillow’s housing and property database. Their analysis included buildings like homes, stores, schools, and hospitals.
The researchers found that a third of the country contained hazard hot spots, but about 57% of structures sit within these hot risk areas. This is especially the case in earthquake- and hurricane-prone areas, where the density of structures has increased faster than the national trend.
What’s more, there are many structures that are at risk for more than one natural hazard. In the western United States, earthquakes and wildfires could occur in the same area, and floods and tornadoes (and sometimes hurricanes) can threaten the middle and southeastern regions. The explosion of development over 7 decades has ballooned the number of structures at risk of multiple hazards from around 173,000 in 1945 to more than 1.5 million in 2015.
The authors note that development patterns should be taken into consideration to fully capture the risk from natural hazards. And they explain that as climate continues to change, monitoring the occurrence and intensity of weather-related events will help refine the hazards of the future. (Earth’s Future, https://doi.org/10.1029/2020EF001795, 2021)
—Sarah Derouin, Science Writer