Isabel may save costliest twist for last
By Richard Stenger
(CNN) -- With punishing winds, surging waves and sheets of rain, hurricanes bring with them a powerful punch that can wreak serious environmental damage. Hurricane Isabel promises to be no exception.
Although the storm system was not one of the strongest hurricanes as it smashed onto the U.S. Atlantic coast, a combination of factors suggest that it could prove to be a devastating one nonetheless.
Much environmental havoc will of course be concentrated around where Isabel made landfall Thursday on the North Carolina coast. The most serious consequences may not occur until later, however, as flooding many miles inland often causes the most deaths, according to hurricane experts.
The colossal physical forces at work when major tropical storms strike the coast are obvious. They can strip beaches of sand, exposing underlying rock, obliterate dunes and create new ones farther inland, and even split barrier islands in half.
The major culprit is storm surges, huge waves that form due to heavy winds and low atmospheric pressure. During the most powerful hurricanes, the combination creates waves up to 15 feet (4.6 meters) higher than normal.
"Storm surges can pose lots of problems for houses right along the coast. The winds may not destroy the homes, but sometimes the storm surge can. Sometimes they even go up and over houses," said Phil Klotzbach, a hurricane researcher at Colorado State University in Fort Collins.
Hurricanes are ranked 1 to 5 on what is known as the Saffir-Simpson scale of strength, with 5 being the most powerful.
Isabel, a Category 2 hurricane, hit North Carolina's Outer Banks early Thursday afternoon shortly before high tide, packing more of a storm surge punch.
A surge could temporarily push the sea level up to 8 feet (2.4 meters) above normal in North Carolina and some neighboring states, according to meteorologists. An area at particular risk is the Chesapeake Bay, which borders some of the most densely populated regions in the Eastern United States.
"Even though the center of the hurricane is not going over it, the winds of the hurricane will drive the water of the Atlantic up the Chesapeake, which could lead to some significant flooding along the shoreline of the Chesapeake," said Jim Candor of AccuWeather, a State College, Pennsylvania-based meteorological service.
The storm surge could push the water level up 3 or 4 feet (1 or 1.2 meters) as far inland as Baltimore, Maryland, Candor said.
The news is grim for that part of the East Coast, which already has weathered one of the wettest years in decades. The surrounding land is saturated. Reservoirs, rivers and streams are full. The region can hardly soak up more.
"If this happened last year, when we were in a drought, it'd be a much different situation," said U.S. Army Corps of Engineers spokesman Peter Shugert.
While the consequences of a hurricane are immediate, some consider the aftereffects to be more of a danger, even if the storm weakens into a tropical storm while it moves over land.
Clouds from such systems can dump more than a foot of rain in a span of hours over a particular area, sometimes many dozens of miles inland, with devastating results.
"It's the day after the storm that we're most worried about," North Carolina Gov. Michael Easley said. "That's when we lost 24 lives to flooding [the day after Hurricane Floyd in 1999]. People driving out in what they thought was 2 or 3 inches of water ended up in a ditch 6 feet deep."
Over the past three decades, inland flooding has been responsible for more than half the U.S. deaths associated with hurricanes and tropical storms, according to Ed Rappaport, deputy director of the National Hurricane Center in Miami, Florida.
CNN/Money's Chris Isidore contributed to this report.