New york dating floods cause havoc across europe
In the past, sediment carried downstream each year would have refreshed the delta.But agriculture, industry and hydroelectric dams have diverted water and choked the flow of sediments, so the land is no longer being rebuilt.As wind and rain erode the mountain range, massive rivers carry more than a billion tonnes of sediment into the Bay of Bengal each year; in some places, the layer deposited since the most recent ice age is more than one kilometre thick.As in all deltas, this loose material compacts easily, causing the land to sink slowly and the relative sea level to rise.The deluge of salty water washed out fields, homes, roads and markets just as people had begun to recover from the damage caused 18 months before by Cyclone Sidr. And thousands more took shelter on what remained of the embankments, where lack of sanitation and privacy would soon spur disease and crime.When Steven Goodbred, an Earth and environmental researcher at Vanderbilt University in Nashville, Tennessee, came across this site during a field trip in 2011, he and his students were shocked to find the land still badly flooded and thousands of families living in tents and ramshackle huts.For subsidence rates in Bangladesh, he says, “depending on how and where you measure, you might get 15 different values”.
“It looked as desolate as the Moon — mud everywhere,” says Goodbred.But those numbers need to be checked against ground-based measurements — which are now on the way.Michael Steckler, a geologist at Columbia University's Lamont–Doherty Earth Observatory in Palisades, New York, has been installing a network of Global Positioning System (GPS) receivers to monitor subsidence since 2003.“I'd never seen anything like it.” He made it his mission to determine how the embankments around the island, called Polder 32 after the Dutch word for land protected by dikes, had been eroded and undermined enough for a relatively small storm to wreak such havoc. About 6,000 square kilometres of the massive Ganges–Brahmaputra delta, the largest delta in the world, lies less than two metres above sea level.On average, 6,000 people in Bangladesh die each year in storms and floods.