“Monday morning I began gathering data for making temporary maps and tables as the hurricane moved inland, just in case anyone wanted to see data immediately. I knew I would be able to fine tune the report after the winds tapered off.”

Only days later he would be doing the process again for Hurricane Rita, which came ashore near Port Arthur, TX, and affected forests in southwest Louisiana and east Texas.

“We’re occasionally called on by States or by the Station for quick assessments,” Jacobs says. “In the case of Hurricane Katrina, Washington officials wanted quick answers.”

Officials need damage estimates to target disaster assistance funds as well as for budgeting State and Federal funds for firefighting, insect and disease monitoring, and forest restoration efforts. Jacobs can provide them with damage estimates within 3 days of a disaster.

Jacobs relies heavily on the availability of two key types of information: up-to-date forest inventory data and near-realtime meteorological details. The inventory data that FIA produces on an annual basis serves as the benchmark that allows the effects of catastrophic events to be measured. The increasingly sophisticated data compiled by the National Weather Service and the National Hurricane Center, immediately available on the Internet, enables Jacobs to create his rapid assessment methods. Jacobs uses data on wind patterns and speeds, rainfall totals, areas of tidal surges, and the path of the hurricane’s eye as it moves inland.

“The eye path is particularly important because the heaviest damage to forests usually occurs on the windward side of the path, where the wind has picked up speed over bodies of water before it hits the shore,” Jacobs says. “With hurricanes on the Atlantic and the gulf, that’s the right side of the eye track.”

Jacobs points out that his rapid assessment procedure is not foolproof, but must take into account variations in geography. For example, his early assessments of damage from Katrina failed to take into account that the path of the hurricane’s eyewall remained over water longer as it moved to its third landfall at the Louisiana-Mississippi border, allowing the wind speed to remain higher as the storm moved into Mississippi. Such details he takes into account in his final reports.

Storm Training

Jacobs got a chance to refine his methodology in early fall 2004, when four hurricanes hit Florida and the Gulf Coast. Hurricane Charley, a category 4 storm, came ashore on the west coast of Florida with winds clocked at 145 miles per hour. A scant 3 weeks later, while Jacobs was evaluating Charley’s effects on Florida forests, Hurricane Frances made landfall as a category 2 on the other side of the State. His office quickly assessed Frances and was returning to work on Charley when Hurricane Ivan roared ashore on September 15 at nearby Gulf Shores, AL.

For Jacobs’ purposes, Ivan proved to be the perfect storm, a model for future rapid damage assessments. The damage map he produced for Ivan shows four concentric zones that radiate outward from landfall at Gulf Shores (see map on page 7). The zone of heaviest damage, zone 4, lies immediately to the right of the landfall site. Each succeeding layer, though showing less damage, increases in size, so that even zone 1 (scattered, ≥1 percent light damage)—which in the case of Ivan reached almost to Huntsville in north Alabama—can represent a considerable economic impact on forest resources.

Before September 2004 was over, Hurricane Jeanne had made landfall near Stuart, FL, and followed the path of Frances up the State, crossing forests that Charley had earlier damaged and eventually covering terrain crossed by Ivan on the Florida Panhandle. The overlap of the damage zones made Jacobs’ work even more difficult, but he was able to provide estimates for Florida and Alabama that were later validated on the ground.

Back to Ground Work

While satellite imaging, aerial photography, and other modern sensing technologies can provide important data, the technologies compass—october 2008 themselves do not provide all the information Jacobs needs. Techniques that work well on western forests are not so accurate on forests in the South. Light detection and ranging (LiDAR) equipment, which measures tree height, works well with forests made up of large trees, open canopy, and sparse understory. Southern forests typically have smaller trees, denser understories, and more rapid change than those out West.

And to assess damage, you have to know what was there before the storm hit.

“We don’t have prestorm LiDAR data on these forests,” says Jacobs. “We really depend on the hard numbers we get from on-the-ground forest inventory work.”

For more information:
Dennis Jacobs at 865–862–2060 or
djacobs@fs.fed.us

 

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