Using tax dollars to move whole communities out of flood zones, an idea long dismissed as radical, is swiftly becoming policy, marking a new and more disruptive phase of climate change. This week’s one-two punch of Hurricane Laura and Tropical Storm Marco may be extraordinary, but the storms are just two of nine to strike Texas and Louisiana since 2017 alone, helping to drive a major federal change in how the nation handles floods.

For years, even as seas rose and flooding worsened nationwide, policymakers stuck to the belief that relocating entire communities away from vulnerable areas was simply too extreme to consider — an attack on Americans’ love of home and private property as well as a costly use of taxpayer dollars. Now, however, that is rapidly changing amid acceptance that rebuilding over and over after successive floods makes little sense. The shift threatens to uproot people not only on the coasts but in flood-prone areas nationwide, while making the consequences of climate change even more painful for cities and towns already squeezed financially.

This month, the Federal Emergency Management Agency detailed a new program, worth an initial $500 million, with billions more to come, designed to pay for large-scale relocation nationwide. The Department of Housing and Urban Development has started a similar $16 billion program. That followed a decision by the Army Corps of Engineers to start telling local officials that they must agree to force people out of their homes or forfeit federal money for flood-protection projects.

“Individuals are motivated. They’re sick of getting their homes flooded,” said Daniel Kaniewski, who until January was FEMA’s deputy administrator for resilience. “It’s not easy to walk away from your neighborhood. But it’s also not easy to face flooding on a regular basis.”