| LINK Newsletter - October 2008
Hurricane Katrina: LiDAR to the Rescue
by Sandra Wade, Marketing Manager, Airborne 1
"We paid for Louisiana’s LiDAR dataset nearly 10 times over.”
--David Gisclair
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| Post-Katrina Flooding (US Coast Guard) |
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I recently spoke with David Gisclair, Technical Assistance Program Director at the Louisiana Oil Spill Coordinator’s Office, about Louisiana’s experience with LiDAR during Hurricane Katrina. I first met him at USGS’s Second National LiDAR Initiative meeting in Reston, Virginia in May, where he discussed the importance of LiDAR to Louisiana’s hurricane rescue and recovery efforts. I found his presentation so interesting that I decided to interview him for the LINK.At the time we spoke, it was close to the third anniversary of the day Katrina hit. Gisclair and his colleagues were busy preparing for Hurricane Gustav, which was approaching the Gulf. Thankfully, Gustav turned out to be much less damaging than Katrina.
Katrina was one of the largest natural disasters in U.S. history. The storm left an estimated 12,000 people homeless and cost billions of dollars in damage. The most severe effects were felt in the greater New Orleans perimeter, which is an area of vast strategic importance. “Andrew Jackson didn’t fight the battle of New Orleans for nothing,” Gisclair pointed out to me in his smooth southern drawl.
Fortunately, this area was covered in a state-wide LiDAR survey conducted well before the hurricane hit in 2005. This survey was part of a pilot FEMA project to modernize floodmaps. Outdated flood maps were making it difficult for insurance companies to adequately assess risks in floodplain areas. Back in 1999, Gisclair and other officials traveled to Washington to advocate federal funding for Louisiana in a map modernization pilot project.
Their goal was to obtain new typography to update hydrologic modeling. Their efforts succeeded. Louisiana (along with North Carolina) was chosen for an updated LiDAR survey. After successfully demonstrating LiDAR technology, Congress appropriated funding for map modernization in 2003. In phase 1 of the project, LiDAR data was acquired for Southeast Louisiana. Phase 1 collected data on every terrain type that might possibly be encountered over the course of the project, so this area was chosen due to its population density and variety of terrain types. Also, most of the low-lying areas were located in Southeast Louisiana.
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| Satellite image of Katrina making landfall (NASA) |
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Louisiana’s LiDAR dataset, slated for completion in 2009, covers approximately 50,000 square miles of the state and was put to the test when Hurricane Katrina hit in 2005. During the 26th Annual ESRI User Conference in 2006, a FEMA official declared the Louisiana LIDAR dataset “the most accessible and valuable geospatial dataset ever encountered in responding to a regional disaster.”
Why did the LiDAR dataset prove to be so valuable?
After Katrina hit in 2005, failures of the federally built levee system left 80 percent of New Orleans under water. As the levees breeched, state officials were able to use the LiDAR data to calculate the depth of water at each intersection of the transportation network (at each node). This was useful for:
1) guiding the travel of military rescue vehicles, which were designed to travel in 4 feet or less of water. Using the node points, they could determine where the transportation vehicles could feasibly go to deliver supplies.
2) in combination with information from USGS hydrowatch stations, calculating the depth of water for every parcel in the greater New Orleans area. Properties with 4 or more feet of water were immediately issued checks by FEMA. Thus, LiDAR data allowed FEMA to circumvent inspection of nearly 1 million properties in the greater New Orleans area, saving millions of taxpayer dollars in emergency assistance.
Gisclair countered the common view that LiDAR is a prohibitively expensive technology. “We paid for Louisiana’s LiDAR dataset nearly 10 times over,” he told me, enthusiastically.
“LiDAR provides a 3D view of the world, so that people can understand what’s going on topographically,” Gisclair said. “But LiDAR is not for the feeble-hearted”, due to its storage and processor requirements.
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| LiDAR map of flooding in New Orleans (NOAA) |
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Despite the resources that a nationwide LiDAR survey would require, Gisclair is a huge advocate for USGS’s efforts to procure funding for one. Gisclair noted that many other states are struggling with out-of-date maps—maps that are woefully inadequate for dealing with emergency management requirements. “It was fortunate that we were able to volunteer for this pilot study, and that our LiDAR survey was completed in advance before tragedy struck. Don’t wait for an emergency,” he cautioned other state GIS officials. “The basic info to respond with must already be in hand.”
Louisiana’s LIDAR dataset is currently being used by FEMA and the insurance industry to determine the flooded depths of individual structures, eliminating the need for expensive field investigations and surveys. The savings in FEMA assistance in the New Orleans area alone paid for the entire state’s dataset, according to Gisclair. I asked Gisclair to speculate how often he anticipated surveying his state. Louisiana officials plan to update their data at least once every ten years; once every 5 years in areas of above-average subsidence.
I highly recommend attending Gisclair’s next speaking engagements to hear more about Louisiana’s experiences with LiDAR. He’ll be speaking at GIS in the Rockies and will be a keynote speaker at the Central Florida GIS Conference in Orlando.
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