Now it’s hazard: We placed our chemical plants near waterways. That used to make sense.

Chemical plants and sites of heavy industry are often located near coasts and waterways; they were originally placed to take advantage of the ease of shipping products by water, and the proximity to water for cooling.

But what was once a practical choice is now becoming a hazard.

When Hurricane Harvey struck Houston in August last year, floodwaters filled with hazardous chemicals, swept away from their containers in Houston's many chemical plants and hazardous waste facilities and into the streets. At the Chevron Phillips chemical plant in the city, 34,000 pounds (about 15.5 metric tons) of highly caustic sodium hydroxide and 300 pounds of benzene, a carcinogen, escaped through a damaged valve after the storm, the Ne w York Times reports.

Apparently, the US should expect many more events like this in the near future. In a new investigation, the Times found that 2,500 US sites that handle toxic chemicals are located in flood-prone areas. Of those, 1,400 are located in areas the US Federal Emergency Management Agency considers “at highest risk of flooding.”

As the effects of climate change worsen—including increased sea-level rise, heavier and more frequent rainfall in some areas, and more intense hurricanes—these sites are poised to become more vulnerable.

Further, the Times only counted locations where companies are actively handling large enough quantities of chemicals harmful to human health or the environment to be included in the federal Toxic Release Inventory; it did not include all the Superfund sites contaminated with historical waste and located in floodplains. As bad as the Times' map seems, the reality is worse.