The Washington PostDemocracy Dies in Darkness

This new mapping technology will show whether global warming could drown your town

A Lidar map of New Bern, N.C. shows potential flooding from a 16-foot storm surge. The image is from a Power Point delivered last year by the director of the North Carolina office of Geospatial and Technology Management.
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While I was reporting this story on sea-level rise on the Outer Banks, it quickly became clear that coastal residents were upset less by the raw forecast (39 inches by 2100) than by North Carolina's decision to take that inherently uncertain projection and map its impact. So even though nobody knows whether the seas will actually rise 39 inches over the next century, North Carolina was producing maps and databases that, with great precision, seemed to declare specific addresses doomed.

This was understandably alarming to property owners. To those who doubt the existence of global warming, it probably felt a little like the government condemning the family homestead because a meteor might strike.

So I wondered: Why aren't homeowners everywhere freaking out about these projections?

Part of the answer, it turns out, is that North Carolina has been an early adopter when it comes to elevation mapping. After Hurricane Floyd practically leveled the place in 1999, the state legislature ponied up cash to become the first state in the nation mapped through a new process called lidar.

Lidar -- which stands for Light Detection and Ranging -- uses airborne lasers to examine the surface of the earth and produce uncommonly detailed and accurate elevation maps. The technology is so revolutionary, it has been credited with locating the legendary Lost City of the Monkey God in an otherwise impenetrable Central American rain forest.

When they commissioned their lidar maps, North Carolina officials were primarily interested in getting a better look at their vulnerability to storm surges and storm-related flooding. But a few years ago, after the North Carolina Coastal Resources Commission produced the 39-inch forecast, the lidar elevation maps were combined with detailed information on houses and other structures in flood plains to produce a stark forecast of expected property damage from sea-level rise.

The entire project was managed by John Dorman, director of the North Carolina office of Geospatial and Technology Management. Dorman did not respond to phone calls and email requests to discuss the program. Dave Maune, the nation's premier lidar expert whose firm has been working with North Carolina, called Dorman a "visionary" who "has been very innovative in letting individual homeowners know the threats to their house."

And Dorman's maps are poised to get even more precise, Maune said: North Carolina is now upgrading its lidar maps to quality level 2, the standard recently adopted by the U.S. Geological Survey (USGS) and other federal agencies.

"John Dorman is probably in the best position of letting the people of North Carolina see, on a house-by-house basis, what the impact of sea-level rise is going to be," said Maune, a senior project manager at Dewberry in Virginia. "Other states are working on doing things like that, but they don’t have the toolbox that John Dorman has."

Other places are catching up, though. Over the past decade, much of the U.S. coast has been mapped with some version of lidar and the results are available on the Digital Coast portal of the National Oceanic and Atmospheric Administration (NOAA). It takes some sophisticated tinkering to overlay those maps with sea-level rise projections. But Climate Central, an independent organization of scientists and journalists, is in the process of performing that task and publicizing the results.

Ben Strauss, director of Climate Central's program on sea-level rise, said the organization's Surging Seas Web site lets users look at potential property damage all the way up to six feet of sea-level rise. Climate Central's maps for Maryland, Virginia and the District are due out later this summer.

Other maps of sea-level rise are also proliferating, and you can do a rough take yourself at the Tumblr site DrownYourTown. Experts on climate change say that as the maps become more broadly available, anxiety about the potential economic effects of global warming could become far more widespread.

"You will probably see a bit more of the conservative backlash as the situation comes clearer and more specifics are proposed," said Duke University marine policy professor Michael Orbach. "That will probably go on for a decade or so. And then people will say, 'Oh, jeez, you're right. We really do have to do something about this.'"