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Drew Kann and Ella Nilsen / CNN

USA - 25% of all critical infrastructure in the US is at risk of failure due to flooding, new report finds

As a massive investment to repair roads and adapt to climate change faces an uncertain fate in Congress, a new report finds much of the country's infrastructure is already at risk of being shut down by flooding. And as the planet heats up, the threat is expected to grow.

Today, one-in-four pieces of all critical infrastructure in the US — including police and fire stations, hospitals, airports and wastewater treatment facilities — face substantial risk of being rendered inoperable by flooding, according to a new report released today by the First Street Foundation, a nonprofit research and technology group that assesses the threat posed by flooding across the country.

The report also found nearly 2 million miles of road — 23% of US roadways — are already at risk of becoming impassable due to flooding.

To provide what First Street says is the fullest picture to date of community-level flood vulnerability, the researchers examined five categories across the Lower 48 and the District of Columbia: Critical infrastructure; social infrastructure, including museums, government buildings and schools; roads; commercial properties; and residential properties.

Gulf Coast and Appalachia especially vulnerable to flooding

In some areas of the United States, nearly all properties, roads and critical infrastructure — such as hospitals and power stations — are vulnerable to failure due to flooding. These vulnerabilities will get worse as the climate warms, according to a new analysis by First Street Foundation.

The report used estimates of operational flood risk from official governing bodies to determine the amount of inundation it would take to knock different types of facilities or services offline. The researchers then overlaid the kinds of flood events that can be expected in an area at least once every two years to gauge community risk.

First Street's past reports have focused on the unknown risk of flooding faced by US homeowners, and the inadequate flood insurance coverage many of them have or, often, don't have. Experts say comprehensive assessments like the new report are critical as the country weighs how to adapt to a climate-altered future.

"Even if your home is safe and secure from a specific intensity of flooding, if flooding is becoming more common and destructive in your community, your property value may be threatened too," said Hamed Moftakhari, an assistant professor of environmental engineering at the University of Alabama, who was not involved with the First Street report.

Where flood risk is greatest today

If there is a ground zero for flood danger in the US, it is Louisiana.

The state is home to six of the top 20 most at-risk counties in the country. Cameron Parish in southwest Louisiana is the most vulnerable county in the US, followed closely by Orleans Parish, which includes New Orleans.

Jeremy Porter, First Street's head of research and development, said while New Orleans has adapted its infrastructure and levees to hold off stronger storms, continued sea level rise and more destructive hurricanes could eventually overwhelm the city's current defenses.

"It's going to have to continually be updated as the environment changes in the future," Porter said. "The infrastructure that's in place today isn't going to protect New Orleans in five, 10, 15 years. That's only going to get worse as sea level rises, as storms not only become more frequent but become stronger."

In both Cameron and Orleans Parish, the report finds more than 94% of all critical infrastructure — including police and fire stations, which are critical to emergency response operations after disasters like hurricanes — are at risk of being knocked offline.

Florida is also home to some of the most flood-prone counties in the country, but flood risk isn't confined to coastal areas. Many areas in Appalachia, like McDowell County in West Virginia and Johnson County in Kentucky, are also among the most at-risk because of the growing threat of heavy rain, the First Street researchers said.

As the planet warms due to human-caused climate change, a warmer atmosphere can hold more water, which makes extreme rainfall events dumping massive amounts of water in short periods of time more likely.

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