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Tracking the aftermath

Dartmouth Flood Observatory provides insight into flooding after Katrina, Rita

Researchers with the Dartmouth Flood Observatory (DFO) have been working with state and federal officials, along with representatives from nongovernmental organizations, to help map and analyze the flooding that has occurred as a result of Hurricanes Katrina and Rita. The maps not only provide an overview of the impact and enormity of the flooding, they also preserve a day-to-day record of the floods to be analyzed in the coming months. The images will also be archived to support research into global flooding trends and climate change.

A Dartmouth Flood Observatory map of the New Orleans area
A Dartmouth Flood Observatory map of the New Orleans area illustrating the extent of flooding in the wake of Hurricane Katrina. Data for the map came from many sources, including the U.S. Geological Survey. (Image courtesy of the DFO)

The DFO's director, G. Robert Brakenridge, said that the partnerships between organizations have been vital to quickly assembling maps that illustrate current flooding and outline other areas for potential flood activity. The DFO was the first to publish on the Internet, on Aug. 31, regional detailed maps of flood inundation caused by Hurricane Katrina. Some of the DFO's maps are used by media.

Brakenridge, Research Associate Professor of Geography, explained that high-resolution data is not needed for initial mapping efforts. In fact, to obtain high-resolution data of specific sites, satellites require lead time to reach the part of the Earth that is involved. Using NASA's MODIS- (Moderate Resolution Imaging Spectroradiometer) equipped satellites, the DFO receives images quickly.

Brakenridge said, "MODIS doesn't provide high spatial-resolution imagery. Each image pixel represents about 250 meters. We can't see individual houses or roads, but the entire Earth is covered, twice per day. The sensors are always on, and always downloading the image data, so we can obtain decent quality imaging of floodwater quickly. That is important. MODIS was not planned at all for its use in natural disasters, but it has proven its utility time and time again."

Brakenridge participates in a daily teleconference with various officials representing FEMA, the U.S. Geological Survey, the U.S. Army and the Army Corps of Engineers, the Environmental Protection Agency, National Oceanic and Atmospheric and the Centers for Disease Control and Prevention, to name a few. On the table for discussion is coordination between the agencies; dissemination of aerial, satellite and field-based data; and avoiding duplication of efforts. This daily exchange of information speeds the map making and map distribution processes. Another helpful asset is the International Charter for Space and Major Disasters. Satellite data from other countries, such as from the French SPOT satellite, was made available to U.S. disaster response organizations, including the DFO, and in agreement with a memorandum of understanding signed by most of the world's space agencies.

Elaine Anderson, Postgraduate Research Assistant at the DFO, processed the data and made the maps for Hurricanes Katrina and Rita. The Hurricane Rita map she produced was based on lower-resolution MODIS satellite data and was online Sept. 26, only two days after the storm hit on Sept. 24. "In contrast, much of the data I used for the Katrina maps was made available to us through the U.S. Geological Survey and through the activation of the International Charter. We got much higher resolution data for those maps. However, it took more time for us to get it," she said.

"University and college research groups, like the DFO, can help improve society's response to natural disasters," said Brakenridge. "We can sometimes be much more nimble than large federal agencies in using satellite data in new ways, and we can more quickly produce inundation maps that might be useful to emergency response personnel."

Brakenridge and his team have distributed similar maps during other flooding events, such as during the tsunami in the Indian Ocean in December 2004, and during the flooding in the Dominican Republic in May 2004. Maps, flood archives and more information are available at www.dartmouth.edu/~floods/.

By SUSAN KNAPP

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Last Updated: 12/17/08