Buying flood-prone U.S. land and protecting it from development would be far cheaper than paying later for flood damage to homes and other structures built there, researchers said Monday.
With floods one of the mostly costly disasters, and U.S. communities and farms facing record ones this year, protecting floodplains appears to be “hugely cost-effective”, said Kris Johnson, North American deputy director of agriculture for the Nature Conservancy, a environmental nonprofit.
The findings, published Monday in the journal Nature Sustainability, should hold true throughout much of the world, said Johnson, a co-author of the research.
Adopting a strategy of conservation versus development could save tens of billions of dollars in the United States in coming decades, the researchers estimated.
But the move would also help marginalized communities who often choose cheaper but riskier properties, then struggle to adapt to, move away from or recover from floods, they said.
As populations grow and cities expand, floodplains offer enticingly flat, accessible tracts for developers.
Johnson and his colleagues identified 40,000 square kilometers (15,400 square miles) of U.S. land likely to be developed by mid-century within the 100-year floodplain.
A 100-year floodplain is land with a 1% chance of flooding each year over the next century, generally before taking climate shifts into account.
The cost to purchase and preserve all of that land – or even all 65 million acres of undeveloped U.S. floodplains – would be lower than the expense of allowing the land to be developed and dealing with later flood damage, they found.
For a substantial portion of the 65 million acres, the savings would be far higher — five times or more, with the land set-aside also offering local environmental benefits, including floodwater storage.
Flood losses have risen in recent years, according to the federal government, averaging more than $3 billion per year since 2000.
A ‘SLAM DUNK’
Johnson said he and the other researchers were taken aback at “how much of a slam dunk the logic of this could be” – though they emphasized that other forms of flood mitigation, such as levees, dikes and flood walls, remained important as well.
The cost estimates also did not include the potential effects of climate change in driving worsening floods, so the likely cost-benefit value could be much greater, he said.
“Floodplains are relatively small but will get a disproportionate amount of new population growth and new development. That just doesn’t make sense,” Johnson told the Thomson Reuters Foundation.
Flooding is the most expensive form of natural disaster, and the first half of 2019 was the wettest on record in the United States.
U.S. cities are increasingly wrestling with how to change regulations, update flood risks or even tear down flood-prone neighborhoods.
Yet nearly all federal programs fail to “adequately value the future development potential of land that will be tomorrow’s subdivisions,” said Chad Berginnis, executive director of the Association of State Floodplain Managers.
“The largest gap in today’s approach to flood loss reduction is recognizing the value and benefits of … not developing in hazardous areas in the first place,” he said in an email.
Acquiring land is only one way to discourage development in floodplains, Johnson said, pointing to far cheaper methods such as zoning ordinances put in place by local municipalities.