Sea level rise and other changes fueled by global warming threaten roads, rail lines, ports, airports and other important infrastructure, according to new government reports, and policy-makers and planners should act now to avoid or mitigate their effects.

While increased heat and "intense precipitation events" threaten these structures, the greatest, most immediate potential impact is coastal flooding, according to one of the reports, by a panel convened by the National Research Council, the research arm of the National Academy of Sciences.

MIKE SALSBURY/The Chronicle (ENLARGE)

Drivers try to navigate a flooded road west of Chehalis, Wash., in December. Flooded roads and subways, damaged railroad tracks and weakened bridges may be the wave of the future with continuing global warming, the National Research Council reported Tuesday.

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Another study, a multiagency effort led by the Environmental Protection Agency, sounds a similar warning on coastal infrastructure but adds that natural features like beaches, wetlands and freshwater supplies are also threatened by encroaching saltwater.

The reports are not the first to point out that rising seas are a major threat. But they offer detailed assessments of vulnerability in the relatively near term. Both note that coastal areas are thickly populated, economically important and gaining people and investment by the day, even as scientific knowledge of the risks they face increases. Use of this knowledge by policy-makers and planners is "inadequate," the academy panel said.

Noting that 60,000 miles of coastal highways are already subject to periodic flooding, the academy panel called for policy-makers to inventory vulnerable facilities — "roads, bridges, marine, air, pipelines, everything," said Henry G. Schwartz Jr., a member of the National Academy of Engineering and chairman of the panel — and begin work now on plans to protect, reinforce, move or replace on safer ground. Those tasks will take years or decades and tens of billions of dollars, at least, Schwartz said. "We need to think about it now," he said.

The agency report offers three estimates for sea level rise by 2100: about 16 inches a century, a rate it said has already been exceeded; about 2 feet, an estimate many scientists regard as optimistic, and up to 3 feet — something the report says would be catastrophic for wetlands and other coastal features but that is "less than high estimates suggested by more recent publications."

The academy report cited similar estimates. The academy report noted, for example, that airports in many large coastal cities are built in tidal areas, often on fill, making them "particularly vulnerable." In metropolitan New York, Newark, N.J., and LaGuardia Airport are particularly vulnerable, Schwartz said.