These maps show where urban sprawl is making big storms more deadly

Jacksonville and Tampa Bay are the Florida regions most at risk from flooding.

Southern Louisiana seems to have dodged a bullet with Tropical Storm Barry. Although heavy rain caused widespread flooding after the storm hit the state Saturday, the region’s two biggest cities, New Orleans and Baton Rouge, were spared the worst.

But nationwide, the threat to lives and property from rain-triggered storm flooding is escalating, with global warming spawning larger, apparently slower-moving storms, and asphalt and concrete covering permeable open ground that would have soaked up rain as cities expand.

Flooding has always posed the main danger when tropical storms come ashore, and historically, the main killer has been storm surge — a sudden rise in sea level caused by low atmospheric pressure and winds blowing onshore. But in the past three years, 75% of the more than 160 deaths from hurricanes making landfall along the US Gulf Coast and Eastern Seaboard have been due to flooding from heavy rain rather than surging seas, according to statistics from the National Hurricane Center.