Researchers combining high-tech laser mapping and economic analysis are part of a new effort to understand a very old problem in Maryland: the effects of the steady retreat of coastlines.
A study released in August by the Department of Natural Resources estimated the impact rising sea levels might have on three low-lying Maryland communities. Towson University researchers determined that the south Anne Arundel County community of Shady Side, hit hard by flooding during Hurricane Isabel last year, could face even greater risks if sea levels in the Chesapeake Bay continue to rise.
This home was razed after flooding from Hurricane Isabel. In Shady Side, a study found that rising waters could make the area even more prone to flooding, potentially causing tens of millions of dollars in damage.
(Courtesy Of Anne Arundel County)
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Their study found that a two- or three-foot rise over the next hundred years would not put Shady Side permanently underwater, a danger for some communities on the Eastern Shore. But the researchers determined that rising waters could make the neighborhood even more prone to flooding, potentially causing tens of millions of dollars in damage.
Counties, universities and state agencies also are creating detailed elevation maps of areas near water. They say these will be useful for predicting which areas will be slowly inundated and which are likely to flood in the next big storm.
"We're all trying to make good decisions, and we need good data," said Ken Miller, who oversees the mapping efforts for the Department of Natural Resources. "Without this kind of information, you're kind of shooting in the dark."
Scientists say the Chesapeake's waters have been rising here for thousands of years: In fact, they helped create the Chesapeake itself, by permanently flooding the Susquehanna River about 10,000 years ago.
"It's essentially a drowned river valley," said Kerry Kehoe, coastal program manager for the Department of Natural Resources.
In more recent centuries, the Chesapeake's rising waters have turned solid islands into marshes and made other islands disappear. The best-known example is Sharps Island, once a 600-acre landmass with farms, a school and a hotel. Its only remnant is a leaning and decayed lighthouse.
In Anne Arundel County, the Maryland Geological Survey has noted that in the mid-1800s a set of small islands called the Three Sisters lay off the Shady Side peninsula. But those also vanished, probably by the turn of the 20th century, said Jeffrey Halka, chief of coastal and estuarine geology.
The reasons for rising sea levels are complex, officials say. Even setting aside theories about human causes of global warming, scientists say that Earth is in a naturally warm period, in which glaciers are melting and sea levels are rising about 1.5 millimeters per year worldwide.
In this area, the Chesapeake rose about one foot in the past 100 years. The land is also sinking because of a natural process called subsidence, lowering about one millimeter per year.
"The combination makes the Chesapeake have a higher rate of sea level rise than many other places," Halka said.
The study released in August was an attempt to take preliminary snapshots of how selected Chesapeake communities might be affected if water levels continue to go up. The three chosen were Shady Side, a dense and eclectic neighborhood on a peninsula south of the West River; the watermen's villages on Upper and Middle Hooper Islands on the Eastern Shore; and the semi-suburban communities of Piney Point and St. George's Island in St. Mary's County.
Researchers from a Frederick County company, EarthData, flew over each site in a small plane, aiming a laser at the ground. The plane sent down 22,000 laser pulses per second, then recorded the height at which each bounced back.
