The "expanding bull's-eye" of hurricane risk

The population density of the Texas-Louisiana coastal region where Hurricane Laura is set to make landfall as a Category 4 storm has increased significantly over the past 40 years.

Why it matters: The damage a storm can do is a function not just of its sheer strength, but the number of people in its path. As more people live in coastal regions, we will get an increasingly "expanded bull's-eye" of hurricane risks.

What's happening: As Hurricane Laura is set to hit the Gulf Coast tonight or tomorrow morning, it has sustained winds of about 140 mph and could cause "unsurvivable storm surges" as high as 30 feet.

• But while the storm's sheer power — and the role that climate change might play in intensifying that power — grabs attention, the more immediate multiplier is the increase in the number of people living in harm's way.

By the numbers: The population of coastline counties in the Gulf of Mexico region increased by more than 3 million, or 24.5%, between 2000 and 2016.

• That's the fastest growth among all coastline counties, and significantly faster than total U.S. population growth over the time period.
• The GIF above, posted on Twitter by the Villanova University geographer Stephen M. Strader, shows the growth in housing density over the past four decades for the region that's in Laura's path.

How it works: The spread of development in natural disaster-prone areas creates what experts call an "expanding bull's-eye" effect of increased risk.

• Imagine the Gulf Coast as a dartboard. As development expands, the bull's-eye — the area where a storm might do maximum damage — expands as well.
• That means more people and more property in the path of a possible hurricane, increasing the damage for a mild storm — and multiplying it for a severe one.

The bottom line: While more and more people move into fire, tornado and flood-prone regions, natural disasters will get worse — even before we begin factoring in climate change.