World's River Deltas Sinking Due to Human Activity: University of Colorado (Boulder) Study

According to Science Daily, a new study led by the University of Colorado at Boulder has indicated that most of the world's low-lying river deltas are sinking from human activity, making them increasingly vulnerable to flooding from rivers and ocean storms and putting tens of millions of people at risk. Despite a 2007 Intergovernmental Panel on Climate Change report that concluded many river deltas are at risk from sea level rise, the new study takes it a step further. It indicates other human factors are causing deltas to sink significantly. The researchers concluded the sinking of deltas from Asia and India to the Americas is exacerbated by the upstream trapping of sediments by reservoirs and dams, man-made channels and levees that whisk sediment into the oceans beyond coastal floodplains, and the accelerated compacting of floodplain sediment caused by the extraction of groundwater and natural gas.

The study concluded that 24 out of the world's 33 major deltas are sinking and that 85 percent experienced severe flooding in recent years, resulting in the temporary submergence of roughly 100,000 square miles of land. About 500 million people in the world live on river deltas.Published in the Sept. 20 issue of Nature Geoscience, the study was led by CU-Boulder Professor James Syvitski, who is directing a $4.2 million effort funded by the National Science Foundation to model large-scale global processes on Earth like erosion and flooding. Known as the Community Surface Dynamic Modeling System, or CSDMS, the effort involves hundreds of scientists from dozens of federal labs and universities around the nation.

The Nature Geoscience authors predict that global delta flooding could increase by 50 percent under current projections of about 18 inches in sea level rise by the end of the century as forecast by the 2007 Intergovernmental Panel on Climate Change report. The flooding will increase even more if the capture of sediments upstream from deltas by reservoirs and other water diversion projects persists and prevents the growth and buffering of the deltas, according to the study.

"We argue that the world's low-lying deltas are increasingly vulnerable to flooding, either from their feeding rivers or from ocean storms," said CU-Boulder Research Associate Albert Kettner, a co-author on the study at CU-Boulder's Institute of Arctic and Alpine Research and member of the CSDMS team. "This study shows there are a host of human-induced factors that already cause deltas to sink much more rapidly than could be explained by sea level alone."

Other study co-authors include CU-Boulder's Irina Overeem, Eric Hutton and Mark Hannon, G. Robert Brakenridge of Dartmouth College, John Day of Louisiana State University, Charles Vorosmarty of City College of New York, Yoshiki Saito of the Geological Survey of Japan, Liviu Giosan of the Woods Hole Oceanographic Institute and Robert Nichols of the University of Southampton in England.

The team used satellite data from NASA's Shuttle Radar Topography Mission, which carried a bevy of radar instruments that swept more than 80 percent of Earth's surface during a 12-day mission of the space shuttle Endeavour in 2000. The researchers compared the SRTM data with historical maps published between 1760 and 1922.

"Every year, about 10 million people are being affected by storm surges," said CU-Boulder's Overeem, also an INSTAAR researcher and CSDMS scientist. "Hurricane Katrina may be the best example that stands out in the United States, but flooding in the Asian deltas of Irrawaddy in Myanmar and the Ganges-Brahmaputra in India and Bangladesh have recently claimed thousands of lives as well."

The study results are pretty damning and we must take steps to halt any further damage to the rive deltas.