Published 10:59 PM EDT Mar 20, 2019
Houses on stilts. Floating buildings. More parks to absorb water. Better maps to warn those at risk.
City planners, builders, engineers and scientists are racing to find new ways for people to make a home as climate change brings increased heavy flooding, dangerous weather conditions and extreme storm surges.
Events in recent days have made clear how urgent the problem is. Heavy flooding that began last week from Minnesota to Missouri has killed at least four people, caused more than $1.5 billion in estimated losses and damages and destroyed more than 2,000 homes. The National Weather Service says flooding in South Dakota and Iowa could soon reach historic levels. In southern Africa, more than 350 people were killed this month after a cyclone and related flooding devastated parts of Malawi, Mozambique and Zimbabwe.
Experts say even as some areas grow dryer and more drought-prone, others will experience more violent and wetter storms as climate change makes global weather more variable and extreme.
For areas experiencing more flooding, which in the United States will include coastal communities and those living near rivers, there is hope. Adaptation and mitigation answers range from the fanciful to the concrete (literally) to the achievable.
A recent book envisions what cities will look like after climate change: Low-lying and coastal cities have been destroyed by rising sea levels and storm surge inundation, even as inland towns struggle with droughts and wildfires. Global megacities have become more compact and are almost completely rebuilt to deal with new norms. São Paulo, Brazil, frequently floods, so homes are suspended above the waters. The Brooklyn borough of New York City is protected by storm-surge barriers, parks while turbines line Gowanus Canal to soak up water and energy from the frequent storms that would otherwise flood the nearby homes.
While these scenarios might seem far-fetched, much of what’s described in “2100: A Dystopian Utopia” by architect Vanessa Keith, is actually based on already-existing technologies, some of which have even been built.
For example, planners know that near river systems, the best protection against flooding is to leave the areas around the watercourse that typically flood as parkland or farmland.
This type of mitigation is common in the Sacramento delta in California and along the Mississippi river, said John Cain, director of conservation for California flood management with the non-profit American Rivers, which works to protect and restore the nation’s rivers. Heavy rains this spring near California filled those flood bypasses but protected nearby cities and towns.
For already-built areas, one response to increased flooding is simply to move.
That was exactly the choice made by the town of Pattonsburg, Missouri, in 1998. After having flooded more than 33 times, the town voted to move as a group to higher ground. The town of Valmeyer in Illinois made the same decision.
If moving is not an option, many areas build levees and dams to protect against flooding. According to the U.S. Army Corps of Engineers, more than 14 million people in the United States live behind levees, in all 50 states. But such barriers carry their own risks.
“Levees and dams only work up to a point and when they fail, they fail catastrophically, like Katrina,” said Cain, referring to the over 50 levee and floodwall failures in the greater New Orleans area in 2005 during Hurricane Katrina. The resulting flooding killed at least 1,833 people.
One option for newly-built areas is creating holding ponds to capture some of the runoff during storms, so that the water doesn’t pour as quickly into the local streams and rivers, said Kenneth Kunkel, a professor of climate science at North Carolina State University in Asheville.
These are common enough nationally that they're listed as a flood mitigation strategy by the Federal Emergency Management Agency. One example is the High Point neighborhood in Seattle, which was redeveloped in the early 2000s to include a stormwater pond to keep the local homes from flooding during heavy rains. It was the first large-scale natural drainage system in the area and diverts 80 percent of the area's stormwater runoff so nearby Longfellow Creek doesn't overflow.
Cheaper over the long term
For private developers and individual homeowners, there are many ways to build more safely in flood-prone areas.
In fact, "it’s actually cheaper to build hazard-resistant homes than it is to build to the minimum building codes and then fix things,” said Jeremy Gregory, a research scientist at the department of civil and environmental engineering at Massachusetts Institute of Technology who studied Katrina and other disasters.
“Over its lifetime, you spend more time on the repairs than on the initial construction costs,” said Gregory, who directs the Concrete Sustainability Hub, which studies how concrete can be used for engineering applications.
Individual homeowners can raise foundations so that their homes themselves are further above ground and less likely to flood. In some areas of Florida and the East coast, homes are beginning to be built on piers, to hold them even higher.
“It’s really an elevation game, is what it comes down to. The higher you are, the less likely you are to get wet,” said William Sweet, a National Oceanic and Atmospheric Administration expert in sea level rise.
The one downside is that while “you can raise your house, you’re still driving through water to get to your house,” he said.
An old-but-new choice is to build houses that are set above ground level, with the first story holding the garage or storage and living quarters up one floor.
This style of home actually goes back to building techniques that people in flood-prone areas have long known, but it became less common as flood insurance became available and people moved often enough that they didn’t have a stake in building for the long term.
In the United States, these types of homes were so common in the Gulf Coast and the Mississippi Delta that the style had a name, the raised cottage. These houses featured living quarters above a raised foundation. This was also cooler in warm climates because air could circulate underneath.
Another simple change that’s happening in New York City involves building owners moving utilities on the roof or higher up, rather than in the basement where they tended to be placed.
“That was a big challenge in Hurricane Sandy, the heating and cooling systems and water heaters were in the basement and were destroyed,” said Gregory.
More extreme is to create homes that can move up and out of harm’s way when waters are rising.
A British company, the Larkfleet Group, is working on an experimental house that could rise on jacks above flood waters. The house could be raised 4 1/2 feet in less than five minutes.
In Holland, 29 percent of which is susceptible to river flooding, water remediation is taken seriously. In the town of Maasbommel, a community of amphibious and floating houses was built that go up and down with the rising of the Maas river. The homes are built on floating concrete barges connected to mooring posts.
No news isn’t good news
One of the biggest adaptation tools is simply information, so home buyers and homeowners, along with their communities, can make informed decisions.
Unfortunately, what’s mostly available are government maps that show 100-year flood and extreme precipitation areas. Created using data from the past, they don't take into account what modern climate models predict as weather patterns change.
“They’re based on the assumption that the future will be like the past and that’s just about the worst assumption that a person could make in our current situation,” said Kunkel.
At the University of California, Irvine, environmental engineering professor Brett Sanders and his team are building computer models that show both historic flooding and areas at risk because of climate change, to give residents access to as much information as is available. He hopes to make the program more widely available as they get more funding.
There’s no magic bullet for dealing with the consequences of climate change. Putting the data into forms people can use isn’t quicky, easy, or cheap. And even once they have the information, “these communities have to make smart choices and tough decisions,” he said.