DANGEROUS FLOODING EXPECTED WITH HURRICANE ISABEL
Sept. 17, 2003 ó A wet spring and summer for much of the East Coast has set the stage for Hurricane Isabel to cause significant flooding. Heavy rains are expected in the Mid-Atlantic region which is particularly moist. The Potomac, Susquehanna and Delaware River basins, as well as smaller streams in New Jersey, Delaware, and eastern portions of Maryland, Virginia and North Carolina bear watching. (Click NOAA over head satellite image for larger view of Hurricane Isabel beginning to lash the U.S. mainland with its powerful winds taken on Sept. 17, 2003, at 5:15 p.m. EDT. Click here for high resolution version, which is a large file. Please credit “NOAA.”)
Since June, locations from the Carolinas northward into Pennsylvania have recorded from 20 percent more than normal precipitation in Columbia, S.C., to almost double normal amounts in the Scranton/Wilkes Barre area of northeastern Pennsylvania. Currently soils are quite wet and streams in the mid-Atlantic area are running higher than normal. As a result, precipitation from Isabel will quickly run off, filling low areas on its way to rivers and streams. With rivers already at high levels, heavy rain could cause significant river flooding.
The public tends to overlook the greater danger of flooding and focus on storm surge devouring coastal areas or trees and telephone poles toppled by winds. What most people don’t realize is that over the last 30 years, more than half of all hurricane fatalities are due to inland flooding.
Already, heavy rain has caused record flooding at a number of locations in eastern Pennsylvania and northern Delaware, including the Lackawaxen River in northeastern Pennsylvania, the Schuylkill River in Philadelphia, West Brandywine Creek in southeastern Pennsylvania, and the Christina River in northern Delaware.
With Hurricane Isabel losing punch and being downgraded from a Category 5 hurricane, NOAA forecasters are concerned that there may be a perception that Isabel is not a dangerous storm, but history shows clearly that any tropical cyclone can be dangerous.
In 2001, Tropical Storm Allison wreaked havoc in the Houston area. Intense rain combined with a slow, meandering motion resulted in as much as 36 inches of rain. Flooding caused by Allison took at least 20 lives. Other notable examples of deadly inland flooding due to "weak" systems include Tropical Storm Alberto (1994), which caused flooding in Georgia that killed more than 30 people, and the remnants of Hurricane Agnes (1972), which first made landfall in the Florida panhandle but caused flooding that killed more than 100 people in the mid-Atlantic region, with almost half of the fatalities in Pennsylvania.
The tragedy of these flooding deaths is the fact that many of them were preventable. Statistics show that most flood fatalities involve people driving their vehicles into harm’s way. As little as two feet of moving water can sweep away most vehicles—even SUVs. While it may appear that water over a road is not deep, even if you are familiar with the area, there is no way of knowing whether the road has been washed away. The inconvenience of being delayed is clearly preferable to losing your life or putting the lives of rescuers at risk. Because of this, NOAA’s advice is to “Turn around, don’t drown.”
Isabel, like many hurricanes, will probably cause both power outages and flooding. Even if you lose power, as long as you are not in imminent danger, avoid leaving your residence if you have to travel through flooded areas—wait for guidance from local authorities. Flood danger information is also available online.
Max Mayfield, director of the NOAA Hurricane Center in Miami, Fla., notes that "We’ve done such a good job of communicating the dangers of winds and storm surge that accompany hurricanes that flooding in now the number one cause of hurricane fatalities. Our challenge is to get the word out that inland flooding, in some cases far removed from where the storms come ashore, can pose serious danger."
WEATHER STATS OF AREAS ALONG THE EASTERN SEABOARD;
2003 (8 months):
2003 (3 months/summer):
2003 (6 months)
August 2003 (12 months):
1999 (12 months)
***These data are all based on 109 years of record keeping by the NOAA Climatic Data Center in Asheville, N.C., except the 12-month data, which are from 108 years of record keeping (1895-present). The NOAA Climatic Data Center is the world’s largest reservoir of archived climate and weather data.
NOAA is dedicated to enhancing economic security and national safety through the prediction and research of weather and climate-related events and providing environmental stewardship of the nationís coastal and marine resources. NOAA is part of the U.S. Department of Commerce.
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