Overwhelming scientific evidence shows climate change is leading to rising sea levels and more extreme storms. But you might not know it by looking at the federal government’s flood hazard maps.

The Federal Emergency Management Agency maps flood plains across the country. The maps are intended to show which areas are likely to flood so that local governments can better plan for disasters. They also determine who must buy flood insurance, and at what rates.

The problem is, many of them aren’t up to date. And even the latest maps don’t take into account the anticipated effects of climate change, which will dramatically impact the potential for flooding.

“They’re a very good tool for understanding what your flood risk was,” said Robert Moore, a senior policy analyst at the Natural Resources Defense Council. “They tell you considerably less about what your flood risk will be.”

When making maps, FEMA looks at the classic features that could contribute to flooding, according to Roy Wright, the agency’s deputy associate administrator for insurance and mitigation. These features account for “today’s risk,” he said, and include, “What the bare earth looks like, what the built environment looks like, what the hydraulics and hydrology look like.” For now, he said, FEMA only maps out future flood risk for communities that specifically request it.

Critics say that as a result, flood-related decisions across the country — from policy and funding to building codes and insurance rates — are based on maps made with historical data that underestimate the risk of disasters. Most have been updated in the last decade, but about 15 percent of maps still date back to the 1970s or 1980s, according to a FRONTLINE analysis of FEMA’s map data. The flood map for New Orleans, for example, was most recently updated in 1984, although a new map should be released this year.

FEMA did not immediately respond to a request for comment on the findings from the FRONTLINE analysis.

“It’s entirely backward looking,” said Michael Gerrard, who directs Columbia Law School’s Sabin Center for Climate Change Law. “The floods of 20 years ago are not as bad as the floods that are going to be 20 years from now. But [FEMA’s maps] only look at historic experience.”

At FEMA, Wright said that the agency is working toward a more forward-looking approach to mapping. In December, a technical committee made several recommendations, and the agency has “done some pilots already in terms of ways we can include [future conditions].”

One barrier to changing the mapping process is money. For years, FEMA was given less than $100 million to update the nation’s flood maps. Funding more than doubled under the George W. Bush administration, then declined again under President Barack Obama. Only in the last year has funding been restored to Bush-era levels. Wright said that for 2016, the president requested a budget of $400 million for mapping, and Congress approved $312 million.

A 2013 report by the Association of State Floodplain Managers estimated that it would cost as much as $7.5 billion to bring FEMA’s maps up-to-date, and then about $275 million annually to keep them current.

Wright said he was “happy to see these higher funding levels.” Asked whether it was enough to accomplish the program’s goals, he said he supported the president’s budget request. “What’s really important is to see these levels sustained,” he said.

But FEMA also faces political hurdles.

A primary purpose of FEMA’s flood maps is to provide the National Flood Insurance Program with a way to determine flood insurance rates. Homeowners with a federally-backed mortgage in an area that the maps have deemed a high flood risk are required to buy into the program, although those who either inherited or own their home outright are exempt.

There are more than 5.3 million flood policy holders in more than 22,000 communities nationwide, according to the National Flood Insurance Program. But at least 9 million people live in a FEMA-designated high-risk flood zone along the coasts, according to a recent study published in the Journal of Coastal Research. That tally also doesn’t include those living along inland rivers, which are also in danger of flooding.

Already, more than 20 percent of all claims are filed by people who live outside of high-risk zones. If FEMA were to expand its maps to anticipate flooding based on future risks, many more Americans could find themselves mapped into riskier categories. This could lead to backlash from homeowners and developers who could suddenly find their insurance rates increasing or building plans running afoul of building codes.

“There’s general agreement on the theory that flood mapping systems should more closely resemble markets and reality, but when push comes to shove it doesn’t happen,” Gennard said. “It’s because of the political outcry from constituents who’d be heard in the short term. And their representatives listen.”

He and other experts point to the Biggert-Waters Flood Insurance Reform Act, passed by Congress in 2012, which allowed FEMA to increase flood insurance rates to make the program more sustainable. Homeowners, including many from New York and New Jersey in the wake of Superstorm Sandy, were outraged to see their insurance rates spike. In 2014, under tremendous pressure, Congress rolled some of the rates back.

“People have been complaining about the National Flood Insurance Program for decades, but every time it comes up for reauthorization, there’s piecemeal fixes,” said Jessica Grannis, adaptation program manager for the Georgetown Climate Center.

The program is up for reauthorization in 2017, which could provide an opportunity for an overhaul of both the program and its mapping policies. But Grannis wasn’t optimistic. “People don’t want to live in a floodplain,” she said — even if, because of rising sea levels, they already do.

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