Image: courtesy ROBERT BRAKENRIDGE, Dartmouth Flood Observatory

New composite surface images from the MODIS instrument on board the NASA satellite Terra are proving themselves a huge help to researchers monitoring the current flooding in Southeast Asia. In fact, this year's floods--the worst since 1961--have forced away hundreds of thousands of people living along the Mekong River in Cambodia. But thanks to MODIS, the Dartmouth Flood Observatory has also dramatically improved their ability to chart innundated areas (right). The maps are so good that ones produced by Dartmouth's Robert Brakenridge using Terra data released last month are guiding relief workers as they deliver emergency food supplies to the regions hardest hit.

"MODIS has made an enormous difference in our flood mapping," says Brakenridge. "MODIS can image most of the world every day, and it views a very wide area." He began work to develop a global flood monitoring system in 1996 with the idea of converting satellite imagery into flood alerts distributed to relief agencies online. In addition to Terra, the resulting Dartmouth Flood Observatory now uses images from the Advanced Very High Resolution on National Oceanic and Atmospheric Administration satellites, the Canadian Radarsat and NASA's Landsat 7 as well.

The United Nations World Food Program is now making good use of the monitoring system. "In areas like Cambodia and Laos where there are weak data collection systems on the ground, the MODIS data will be our first-hand information to identify the areas we need to visit and assess for ourselves," says Mahadevan Ramachandran, the program's mapping officer in Phnom Penh. And Brakenridge points out another less immediate application: "We have to know how big a flood event is and keep a global record of such events in order to determine if climate change is accompanied by changes in the frequency and magnitude of big floods."