Floods in BangladeshA large portion of Bangladesh was awash with floods when the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite captured the top image on August 3, 2007. The low-lying nation is an alluvial delta, and therefore, is extremely prone to flooding. In July 2007, heavy monsoon rains filled the Brahmaputra, Padma, and Meghna Rivers, leading to the floods shown here. The Jamuna, a branch of the Brahmaputra River, arcs through the center of the scene, its braided waterways woven into a single thread where the river is overflowing. A branch of the Jamuna flows east into the Meghna River. The wetlands that surround these rivers are full of water, and the rivers themselves are swollen. The Padma River, formed by the convergence of the Ganges and Jamuna Rivers, is also flooded.
The severity of the floods can be seen in the contrast between the top image and the lower image, which was taken on May 1, 2007, before the monsoon rains began. In the dry season, the course of each river is clearly defined, not blurred by excess water. The images were made with infrared and visible light to increase the contrast between water and earth. In this type of image, water is black or blue, where colored with sediment. Plant-covered land is bright green, and bare earth or lightly vegetated areas are tan. Light blue and white clouds dot the scene. In the lower image, red dots mark the location of fires.
The floods shown here stranded hundreds of thousands of people in Bangladesh, one of the world’s most densely populated nations, reported BBC News. As of August 3, nearly 20 million people had been displaced by monsoon flooding in Bangladesh, India, and Nepal, added BBC. Some of the floods in northeastern India were visible when Aqua MODIS flew over on August 3. The intense rains of the summer monsoon typically fall between June and October, so additional flooding is likely.
Flooding in IndiaAbutting the southern front of the snow-clad Himalaya mountains, the broad, flat Ganges Plain is laced with rivers that transport glacial melt to the Bay of Bengal or the Arabian Sea. Not surprisingly, these rivers lead something of a schizophrenic life: during the dry winter, the rivers are small and sedate, their headwaters largely locked in ice. In the summer, temperatures in the mountains climb, melting mountain-top snow and fueling the Asian monsoon, and the rivers swell into roaring giants.
Not every year is the same however—the monsoon may be wetter in a particular year or winter snows might be greater, leading to more snowmelt—and 2007 numbered among the more extreme flood years. Heavy rain throughout July pushed the Ganges and its many tributaries over their banks, submerging large tracts of land in northeastern India. As of August 3, nearly 20 million people had been displaced in India, Bangladesh, and Nepal, and 125 had died in India, reported BBC News.
Among the most severely hit states was India’s northeastern Bihar state. The Moderate Resolution Imaging Spectroradiometer (MODIS) flying on NASA’s Aqua satellite captured the top image of flooding on the Ganges and its tributaries on August 3, 2007. The lower image, captured by Aqua MODIS on June 4, 2007, shows the plain before the summer monsoon and snowmelt swelled the rivers.
In these images (made with a combination of infrared and visible light), water is black or dark blue. Water takes on a brighter shade of blue when tainted with sediment. Clouds, pale blue and white, are scattered over the flooded region, which is bright green with vegetation. Sparsely vegetated areas or bare earth in the lower image are rose-tinted tan.
On August 3, the Ganges, Gandak, and Kosi Rivers were so swollen that it is hard to see exactly where the rivers normally flow. The tributaries that feed the Kosi River, not even visible on June 4, have combined in a vast web of water-covered land. The light blue area under the clouds in the lower left corner of the image is probably water-soaked earth, not standing water.
Though destructive, seasonal flooding in the Ganges River system blankets the plain with fertile alluvial soil, making it productive farmland. Because the plain is so fertile, it is one of the most densely populated regions on Earth.