An hour-long lecture by two University of Maryland scientists on the lessons learned from Hurricane Isabel delivered two main messages: Rising water is more dangerous than roaring wind, and the threat from hurricanes will only get worse.
Last month's presentation at the Chesapeake Biological Laboratory in Solomons took place two years after Isabel, as a Category 2 storm, passed through the region, causing major flooding and power outages in Maryland, Virginia and the District.
The two scientists, William C. Dennison and Donald F. Boesch, vice president and president, respectively, of the University of Maryland Center for Environmental Science, ticked off the region's successes and failures in dealing with the 2003 storm.
Chief among the failures, they said, was the inability of experts to alert the public about the dangers of the storm surge.
"We need better visualization of storm surges," Dennison said. "Forecasters had a good idea of what was going to happen but didn't have any way to visualize it so that people can see how their houses would be affected."
Dennison displayed a model of the water height as the storm moved into the bay, pushing saltwater up into the mouth of the bay and its many tributary rivers. Such displays, he said, were just as relevant as maps of the wind in terms of understanding the overall damage brought by a storm.
In fact, water is even more dangerous than wind, he said: "One hundred-and-fifty-mile-per-hour winds are very scary, but they don't kill people. Storm surges do."
In the second of the two lectures, Boesch warned the audience of 40 people that hurricanes are becoming more powerful. He cited a recent study showing that the number of named hurricanes had not changed over the years, but the number of Category 4 and 5 storms -- those with the strongest winds -- had increased significantly.
Global warming, Boesch said, is a reality that will add to the ferocity of hurricanes. In the Chesapeake Bay, he said, the effects of hurricanes will be accentuated not only by the rise of the oceans but also by the slow sinking of the land caused by a geological process known as "glacial rebound."
Glacial rebound, combined with global warming, means that the Chesapeake Bay rises four millimeters a year relative to the land, Boesch said. High relative sea level means storm surges will be larger.
Dennison said that the track of a hurricane once it lands is one of the most important factors in predicting the location and the extent of storm surge damage. In planning, it is important to look for previous storms that have taken the same track to see what damage was done to the region's lands and waterways.
The two scientists compared Isabel with a 1933 hurricane known as the "Storm King," which also swept into the region just west of the Chesapeake Bay and caused similar damage.
Isabel's storm surge overwhelmed bulkheads and other manmade barriers, reinforcing the advisability of maintaining soft shorelines with breakwaters in front and natural marshes just beyond, Dennison said.
By flushing so much soil and nutrients into the bay, Isabel's storm surge caused a large algae bloom, turning parts of the bay green and depleting it of oxygen. Two years later, bay grasses are significantly scarred.
Some of the fish populations, however, benefited from the storm. The number of croakers and bay anchovies increased, and some marshes gained mud, the scientists said. But, in general, the bay took in a lot of saltwater, which hurts its ecology.
Most people in the audience remembered living through Isabel. Phyllis Bonfield and Marcia Seifert said they had an especially vivid experience with the damage it caused. Their home is atop Calvert Cliffs, which were badly battered and eroded by the storm.
"When the hurricane hit, it wiped away everything protecting our cliff," Bonfield said.
From June 2003 to July 2004, they lost 35 feet of property, leaving 12 feet between their house and the cliff's edge.
The review of Isabel's lasting impact was made especially poignant by the aftermath of Hurricane Katrina, even though the flooding along the Chesapeake Bay paled in comparison with the destruction on the Gulf Coast.
"When we saw people on rooftops, we wondered if this was a bad time to be talking about hurricanes in the abstract," said Jack Greer, assistant director for public affairs at Maryland Sea Grant College. "But we decided it was a good time because hurricanes are only going to get stronger."