Buying and protecting undeveloped flood-prone land in key parts of Minnesota — around the headwaters of the Mississippi, on the North Shore and just south of the Twin Cities — would be far cheaper than paying later for inevitable flood damage to homes and businesses that might be built if the land is not protected, a group of conservation researchers said Monday.

Throughout most of the United States, and particularly along the Mississippi River, it would cost taxpayers less to buy and conserve the vacant land in most floodplains now than to pay out federal flood insurance claims and disaster recovery funds over the next 30, 50 and 100 years, the researchers found.

“These flood disasters just keep happening,” said lead author Kris Johnson, deputy director of agriculture for the Nature Conservancy. “It’s cheaper sometimes, not always, but sometimes to be proactive. Here the ounce of prevention is cheaper than the pound of cure if we can nudge development out of harm’s way.”

The research, produced by the Nature Conservancy and the University of Bristol and published in the journal Nature Sustainability, comes as Minnesota and North Dakota push forward with a flood diversion project around the Fargo-Moorhead area that will cost hundreds of millions of dollars, and as communities throughout the state grapple with increasing flood damage to crops and businesses and outdated storm pipes and infrastructure.

This year is on track to become the wettest year on record for the contiguous United States. Flooding has become the country’s most common and costly form of disaster, causing an average of more than $8 billion in damage a year since 2000, according to the study.

Floodplains act as a kind of natural pressure valve, allowing water to collect harmlessly when rivers overflow.

Researchers found more than 400,000 square miles of unprotected land in the United States that lies within 100-year floodplains — land believed to have a 1% chance of flooding every year. The cost to buy and preserve all that land — some $306 billion — would still be less than the expense of addressing flood damage if that land were developed according to current growth projections from the U.S. Census Bureau and the U.S. Environmental Protection Agency.

In places where land is relatively cheap and the population is expected to grow rapidly, such as St. Louis County and central Minnesota around the Mississippi headwaters, the savings would be far greater — up to five times more — than allowing that land to be developed.

The savings could be even greater than the study estimates, Johnson said, because it does not take into account climate change, which in Minnesota is causing more extreme downpours and more frequent flooding.

Johnson also said that taxpayers could accrue the same savings without buying much of the land if cities and states enforced stricter zoning and development codes within flood plains or offer incentives for developers to build in less risky areas.

States around the country have spent years and billions of dollars buying up and tearing down businesses and entire flood-prone neighborhoods.

But flood-prevention programs of the Federal Emergency Management Agency (FEMA) rarely, if ever, focus on preventing that development in the first place, said Chad Berginnis, executive director of the Association of State Floodplain Managers.

“This is a huge problem with our approach,” Berginnis said. “You just can’t buy out vacant land through federal programs even though it gets so much more expensive when there is a home or business on that property.”

The communities that have proved to be the most flood resilient incorporate the concept of avoidance into everything they do, Berginnis said.

“Whether it’s through subdivision codes, deed restrictions, local buyouts, in some cases it’s just best to avoid hazardous areas,” he said. “This paper shows that we need to make sure our programs work to protect these floodplains.”