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Sunday, October 07, 2007

Lasers to Refine Storm Evacuation Lines
By Duane Marsteller

The recommendation about whether you should stay or go when tropical weather threatens Manatee County might be changing next year.

Local emergency management officials are hoping to use more accurate laser-mapping data, now being collected by the state, to refine Manatee's evacuation zones for the 2008 hurricane season.

That's a year later than officials originally expected. They had anticipated changing the zones for the current hurricane season that ends Nov. 30, using data collected in 2003 as part of a $3.2 million pilot project funded by the Federal Emergency Management Agency.

But they scuttled those plans earlier this year at the urging of state emergency management officials, who now are mapping Florida's entire coastline.

"It's better to wait for more accurate and complete data," said Laurie Feagans, Manatee's emergency management chief. "It'll be worth the wait."

Feagans also said Manatee's mapping data had "some abnormalities," including problems determining where to place parcels that fell into two or more potential evacuation zones.

It also fell victim to a bill passed last year that allocated $25 million toward the statewide mapping project. Contractors hired by the Florida Division of Emergency Management began mapping the state's roughly 1,350 miles of coastline in May, spokesman Mike Stone said.

The contractors are using a technology called Light Detection and Ranging that scans the ground from above with a near-infrared laser to calculate elevations. They will map 15,500 square miles in all, said Richard Butgereit, the agency's geographical information systems administrator.

Another 4,000 square miles farther inland, including around Lake Okeechobee, are being mapped by FEMA and local agencies, he said. That and the state data will be added to another 12,000 square miles recently mapped by local agencies and water management districts.

That does not include Manatee's 2003 data.

"A lot of existing LIDAR data didn't make the cut because it didn't meet the level of accuracy required," said Betti Johnson of the Tampa Bay Regional Planning Council, which is coordinating the mapping effort in Manatee, Hillsborough, Pasco and Pinellas counties.

The laser mapping's vertical accuracy is within centimeters, significantly better than federal government maps now widely used to determine storm surge potentials and establish evacuation zones. Those maps can be off by several feet, especially in rapidly growing areas such as southwest Florida, officials said.

Officials said the increased accuracy is vital because the new data will be plugged into computer models to calculate new storm surge potentials, which evacuation zones are based on.

"It might be the HD (high definition) version of what's going on in television these days," Stone said. "Our local emergency management agencies will be armed with better information and make better-informed decisions."

Copyright by The Bradenton Herald