Many people live blissfully unaware that they have built their homes in a floodplain until torrents of raging water sweep away their houses. So rare are extreme floods, which sometimes occur only once every 50 or 100 years, that as the waters recede, so do people's memories of where the flood waters flowed.
Geography Professor Bob Brakenridge leads the Dartmouth Flood Observatory in working to change this situation.
The team, comprised of Brakenridge and research assistants Amy Stender and Elaine Anderson, develops new techniques "in using satellites to detect and map river floods," Brakenridge said.
"We map floods as they occur as quickly as possible," he said. Researchers at the College, working with other project members at the University of California at Santa Barbara, the University of Arizona and the University of Maryland, create maps of floods from information gathered by satellites.
"Within the U.S. it is not possible to obtain accurate maps of where past floods have actually occurred, [of] what land was under water," Brakenridge wrote in a BlitzMail message.
One of the most important satellites the Dartmouth Flood Observatory uses is the Radarsat, a satellite built by the Canadian Space Agency and launched in 1995 by NASA as part of a shared project between the two space agencies.
Radarsat, which uses radar to produce images, can operate under conditions in which most other satellites are blind.
"It illuminates the earth itself and creates images out of the reflections. Unlike most other satellites, it can go through cloud cover and work at night," Brakenridge said. "It's the perfect tool for imaging flood events through the cloud cover."
The Flood Observatory, funded by NASA Earth Science Enterprise grants, also makes use of other NASA satellites. Brakenridge said a new satellite, Terra, will be available to researchers at the College when launched in early September.
With the data retrieved from the satellites, Dartmouth researchers create maps of the floodplains and post their findings on their website, www.dartmouth.edu/artsci/geog/floods/index.html.
According to the Dartmouth Flood Observatory website, the posted maps and measurements are meant "to facilitate research into the occurrence and causes of extreme flood events, to provide international notice of such events, and to facilitate access to satellite-based measurements and mapping."
Brakenridge elaborated further in a BlitzMail message.
"No one else has ever attempted to record, catalog, and objectively measure floods on a global basis. This is what we are trying to do...record these events just as rainfall," or other routinely monitored environmental conditions.
Brakenridge continued in his message to say nations have shared climate data even during the Cold War, but never included measurements of river discharge or flooding.
The site lists floods reported this month in Iowa, Iran, China, Australia and Nevada, as well as links to other international flood reports.
"I think the cool thing, from my standpoint, is we have a global scale," Brakenridge said.
Catastrophic floods, he said in his BlitzMail message, kill thousands and thousands of people worldwide each year.
"The people most affected are often those most desperate due to other circumstances such as poverty, overcrowding, and civil war," such as the civil wars in Africa during which refugees camped along major rivers.
Brakenridge said via BlitzMail that new techniques in the detection and measurement of extreme flooding will hopefully help avoid or relieve the effects of such natural disasters.
"We're working on the flood in Iowa right now," he said. "We are about to send to NASA an animation showing a flyover of Cedar Creek, Iowa, currently in flood, based on satellite data received here at Dartmouth."
