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Floodwaters from Hurricane Isabel nearly five years rose much higher than expected at the Colonial Beach Yacht Center. Marine scientists are using data from Isabel to forecast storm surges more accurately across the region. |
By RUSTY DENNEN
Twice in the past five years, Kyle Schick had serious flooding at his Colonial Beach marina.
The 12-foot storm surge on the Potomac River from Hurricane Isabel in September 2003 caused extensive damage at Colonial Beach Yacht Center. And, in September 2006, it was swamped with an eight-foot surge during Tropical Storm Ernesto.
In both instances, the predicted storm surge--how high the water could pile up--was significantly below what actually happened.
So, for Schick and thousands of property owners and businesses across the Chesapeake Bay watershed, more accurate and localized storm-tide predictions could give them more time to prepare and help reduce damage.
To that end, the Virginia Institute of Marine Science is working on a computer model so detailed that it could focus on a particular street, for example, and trim the margin of error in such forecasts to centimeters of water, rather than feet.
VIMS, located at Gloucester Point, is one of five graduate schools of the College of William and Mary.
Harry Wang, an associate professor at VIMS and team leader of the project, said that street-level predictions could be available within five years.
"What we want to do is give more warning that's more specific," Wang said. It's timely as the state heads into the 2008 hurricane season, which began June 1 and ends Nov. 30.
The National Weather Service again this year is forecasting an above-average number of storms, some of which could affect the East Coast.
Current forecast models, Wang says, are good in that they give ranges within a few feet of what can be expected.
"But it doesn't tell you if water is coming up to your doorstep or coming into your living room," he said.
Working with other government agencies and two private companies, Wang's team is developing a computer model that could be that precise.
The researchers are developing a grid of the Bay shore that, combined with new LIDAR aerial-mapping technology, allows them to show land features with much finer resolution than traditional methods.
Wang's team used the flooding in the wake of Hurricane Isabel in the Potomac in its pilot study. The model reproduced flood levels within centimeters of those actually observed.
Wang says emergency managers could use the information to alert individual neighborhoods about protective measures and possible evacuation.
Predicting storm-tide flooding in the Bay is a challenge because of its massive scale and topography. The Chesapeake, the largest estuary in the Americas, has 11,000 miles of shoreline, including creeks, coves, rivers and their tributaries.
Wang says the model isn't perfect--yet. Laser detection and mapping elevation data is needed to accurately simulate flooding along any particular stretch of shoreline.
Maryland has mapped its entire shoreline using the laser technology; Virginia has just begun.
Also, the current model takes an hour to simulate each day--too slow for operational forecasting. And, finally, the arrival of the storm surge must be figured precisely with astronomical tides.
If the surge of water pushed by storm winds arrives at high tide, flooding could be up to four feet higher than at low tide.
Schick, the Colonial Beach marina owner, says the more information, the better.
"It would be a huge benefit to have more accurate tide surge predictions," he said.
Before Isabel struck, boats and equipment were moved to higher ground.
"We have a hurricane plan. If they're calling for a 6-foot tide surge, we know boats on shore and certain things in proximity will be safe. If that turns into an an 8-foot tide surge, as was the case in Ernesto, or 12 feet for Isabel"
The National Hurricane Center in Miami uses the Sea, Lake and Overland Surges from Hurricanes model, which is generally accurate to within plus or minus 20 percent in its storm-surge predictions. That's being enhanced to provide information on extra-tropical storms such as nor'easters.
Rusty Dennen: 540/374-5431
Email: rdennen@freelancestar.com
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The Virginia Institute of Marine Science storm-tide prediction project is being developed as part of the Chesapeake Bay Inundation Prediction System. It is funded by the National Oceanic and Atmospheric Administration and includes the Virginia Department of Emergency Management, National Weather Service, U.S. Geological Survey, NOAA's Chesapeake Bay Elizabeth Smith, an oceanographer on the faculty of Old Dominion University, is CIPS project coordinator. She's the liaison between the scientists and end users--meteorologists, local and state emergency managers and those who will pass information along to the public. "There's a high need" for better models, she said, given that the Bay is whipped not only by hurricanes, but by other destructive storms such as nor'easters. For now, the focus of the project is on the Potomac River and the Hampton Roads area. The University of Maryland is working on a similar model for Talbot and Dorchester counties on the Bay. "We're targeting those through the CIPS project at the highest resolution and working very hard to identify funding," Smith said. Eventually, the entire Bay and its major tributaries could be included. --Rusty Dennen |
| The 2008 Atlantic season began June 1, and another active season is predicted.
The National Oceanic and Atmospheric Administration last month forecast 12 to 16 named storms, including six to nine hurricanes. The season runs through Nov. 30. Colorado State University, which does an annual seasonal forecast, is predicting 15 named storms, including eight hurricanes, four of them major. The team said there is a 69 percent chance that at least one major hurricane will make landfall somewhere on the U.S. coastline, compared to the long-term average probability of 52 percent. --The Associated Press |
