Word: sediments
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Dates: during 2000-2009
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...such force is the Mississippi River. Once, the Gulf of Mexico extended north to Cape Girardeau, Mo., but the river gradually deposited enough sediment into a receding sea to create tens of thousands of square miles of land stretching south to the present mouth of the river. Long after New Orleans was first settled, the entire region remained above sea level and safe from hurricanes. Engineers prevented river floods by building levees and kept shipping channels open by constructing jetties two miles out into the ocean so that the river dropped its sediment into deep water. Before the jetties were...
...been plagued from the start by unintended consequences. To prevent catastrophic floods like the 1927 disaster that left 700,000 people homeless from Illinois to Louisiana, the Corps leveed and streamlined the Mississippi. That effort turned the meandering, porous waterway into the world's largest high-pressure hose, shooting sediment and nutrients off the continental shelf in the Gulf of Mexico. Starved of silt and undermined by oil-drilling operations, the delta has been sinking at the same time global warming has caused water levels to rise. The result: every half an hour, a chunk of land about the size...
...western Louisiana coastline, similarly deprived of Mississippi river sediment, has been losing, in some places, as much as 35 ft. of beach a year, according to biologist David Richard, a specialist in the area's wetlands. By the time Rita hit, he says, the Gulf of Mexico was more than a quarter of a mile closer to the inland cities than it was when Hurricane Audrey struck...
...problem. His idea: to redirect a branch of the Mississippi through the heart of Terrebonne Parish, the most densely populated in the delta. Shipping lanes would remain routed through New Orleans, but much of the Mississippi would be diverted at Donaldsonville, 90 miles upriver from the city, so sediment-rich waters could revive the ancient riverbeds in the central delta and rebuild marshland long since lost to the Gulf. Many local groups, including the Terrebonne-based Restore or Retreat, support the idea. One major impediment: parish residents who for generations have built homes and planted sugar-cane crops along...
...then there's the Glen Canyon Dam on the Colorado, which after its completion in 1963 not only robbed the Grand Canyon of sediment needed to rebuild sandbars and beaches but also drowned a spectacular landscape far bigger than the Hetch Hetchy Valley. Thanks to a multiyear drought that has only recently eased, the landscape has begun to re-emerge, energizing an effort by the Glen Canyon Institute to correct what conservationist David Brower called "America's most regretted environmental mistake." It's bound to be an uphill battle. The Glen Canyon Dam is part of the seven-state Colorado...