Earth Protect Blog

By Aubrey Rhoadarmer

Special to The Longmont Times-Call

More than half the structures in the United States are at risk from natural hazards — such as floods, earthquakes and wildfires — according to a new study published in the American Geophysical Union Journal Earth’s Future.

Led by a University of Colorado Boulder research team, the study — entitled “Risky Development: Increasing Exposure to Natural Hazards Exposure to Natural Hazards in the United States” — explains that environmental changes and global warming are factors in this increasing danger, but are not the only culprits. The way humans are developing land, cities and towns is similarly contributing to this trend.

“Every year we lose billions of dollars, we lose lives, to natural hazards, so we wondered why this is happening,” said Virginia Iglesias, a research scientist with the CU Boulder Earth Lab and lead author of the paper. “On the one hand, we know that climate change is increasing extreme events, but we asked if losses could also be increasing because we’re developing in the wrong areas.”

To evaluate how development has affected natural hazard risk, Iglesias and her team compared maps of earthquake, wildfire, tornado, hurricane and flood hazards to a dataset of historical land use derived from Zillow’s housing and property database. The researchers identified “hot spots” as areas where the probability or intensity of the hazard exceeded the 90th percentile for the entire United States.

The study concluded that while only 31% of the United States is considered a hot spot for natural hazards, 57% of U.S. structures are in those regions. Within these areas are 1.5 million structures, all of which are at risk.

“These critical levels of exposure point to our inability, lack of knowledge or unwillingness to limit development in hazardous zones,” the paper reads.

The research revealed there are two distinct processes that have contributed to the increased risk from natural hazards: densification and expansion. Densification is the addition of structures to previously developed lands, and expansion is the addition of structures into formerly undeveloped areas.

In areas most likely to experience earthquakes, development over the past several decades has been driven by densification, while in areas most likely to experience flood, wildfires or tornadoes, development has been driven by expansion. These developments are increasing the areas’ risk from natural disasters. Unfortunately, many of the highest-risk areas also have the lowest income.

“There’s quite a lot of research that shows that natural hazards increase social inequality because the ones who have less and are more vulnerable to begin with lose more, and it takes them longer to recover,” Iglesias explained.

The authors of the paper hope their research can assist city planners and governments with future construction initiatives and help prevent this increasing social inequality.

“Hopefully we can build better in the future, and we can have new policies to reduce vulnerability,” Iglesias said.

But this is not the end of the team’s research. In the future, the researchers are hoping to add onto this study by shifting their focus to loss data rather than just exposure. They will analyze what types of structures are more vulnerable to natural hazards and provide data for loss prevention.

“If we make this information available to people, that can reduce losses dramatically,” Iglesias said. “Information is key.”