NORFOLK, Virginia (Reuters) - The signs of rising water are everywhere in this seaport city: yellow "Streets May Flood" notices are common at highway underpasses, in low-lying neighborhoods and along the sprawling waterfront.
Built at sea level on reclaimed wetland, Norfolk has faced floods throughout its 400-year history. But as the Atlantic Ocean warms and expands, and parts of the city subside, higher tides and fiercer storms seem to hit harder than they used to.
Dealing with this increased threat has put Norfolk at the forefront of American cities taking the lead on coping with intense weather, from floods to droughts to killer heat, without waiting for the federal government to take the lead.
In Norfolk, home to the largest U.S. Naval base and the second biggest commercial port on the U.S. Atlantic coast, floods are a perennial problem that has worsened in recent decades, Assistant City Manager Ron Williams Jr told Reuters.
The relative sea level around Norfolk has risen 14.5 inches (.37 metre) since 1930, when the low-lying downtown area routinely flooded. The floods are worse now, because the water doesn't have to rise as high to send the river above its banks and into the streets, Williams said.
At the same time, severe storms are more frequent.
"We've had more major storms in the past decade than we've had in the previous four decades," he said.
Extreme rainfall events have increased too.
Williams does not call what's happening in Norfolk a symptom of climate change.
"The debate about causality we're not going to get into," he said.
Still, many scientists see the frequent flooding as consistent with projected consequences of rising global temperatures, spurred by increased emissions of greenhouse gases.
No matter what city leaders call it, some of their actions speak louder than words.
Williams said Norfolk, a city of 243,000, needs a total investment of $1 billion in the coming decades, including $600 million to replace current infrastructure, to keep the water in its place and help make homes and businesses more resilient.
Paying for it will be a burden, Williams said. The city is working with the state legislature and the U.S. Army Corps of Engineers, and hoping federal block grants will help too.
One proposed project, a flood wall to protect the historic Ghent neighborhood and others, would cost an estimated $20 million to $40 million.
Williams said a similar barrier completed in 1970 banished perennial floods from what is now the high-rise downtown. That provided a great return on a $5 million investment, Williams said, with $500 million in assessed real estate value in the area that used to flood but now doesn't.
These measures have made Norfolk a leader for other coastal cities on how to adapt to climate change, said Cynthia Rosensweig, a NASA climate scientist who advises New York City on its response. Rosensweig, Williams and others note that building resilience into infrastructure before disasters hit is far less expensive than rebuilding afterwards.
Henry Conde, a retired U.S. Navy captain who lives in Ghent, said he and his neighbors feel the flood threat viscerally: "There's a low-grade fever, so to speak, or an awareness throughout the year. People are always on edge."
Armpit-high waders, stand-alone generators and sump pumps are standard equipment for when the floods come and the power goes out, Conde said in an interview at his 115-year-old home. Winter nor'easters can be just as bad as summer hurricanes and preparing for the worst beforehand instead of mopping up later is simply an economic reality, he said.
Superstorm Sandy's strike on New Jersey and New York in late October heightened awareness of the need to prepare for incoming water. Sea levels are rising along almost every part of the U.S. coastline, except in Alaska, according to the National Oceanic and Atmospheric Administration ( here ).
Nearly three-quarters of U.S. cities see environmental shifts that can be linked to climate change, but they lag behind the rest of the world when it comes to planning how to adapt to these changes and assessing how vulnerable they are, according to a survey by the Massachusetts Institute of Technology and the non-profit International Council on Local Environmental Initiatives, or ICLEI.
U.S. cities have traditionally focused more on mitigating climate change than adapting to it, the opposite of most cities in the developing world, where vulnerability to climate-fueled natural disasters is already high, said ICLEI's U.S. program director Brian Holland.
More than 1,000 city leaders have signed the U.S. Conference of Mayors Climate Protection Agreement (here), in which they promise to try to beat global targets to cut greenhouse gas emissions in their communities and urge Congress to pass carbon-cutting laws.
But labeling it global warming can be dicey, given that there is still controversy, particularly among politicians, over whether human activity is contributing markedly to increasing temperatures.
"Given the politicized view of climate change in this country, it seems that some cities are emphasizing risk management - that way they can get on with the important tasks of reducing risk and safeguarding local residents and municipal assets," said MIT's JoAnn Carmin, author of the 2012 survey of 468 cities worldwide, including 298 in the United States.
Still, city leaders can often reach consensus and act more easily than some members of Congress can, said Jim Brainard, the Republican mayor of Carmel, Indiana, and head of the Energy Independence Task Force for the U.S. Conference of Mayors. One reason for this is that lobbyists opposed to climate measures rarely target mayors or other community leaders, he added. (Reporting By Deborah Zabarenko.; Editing by Ros Krasny and Andre Grenon)