Word: sediments
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Dates: during 1980-1989
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...alarming rate of one acre every 16 minutes, has already drawn up an ambitious mix of programs. In the biggest project, a $24 million pumping station would divert millions of gallons of silt-rich Mississippi River water onto the coastline to help stop saltwater intrusion and to supply sediment that will build up the eroding land. At least one parish is considering plans for a backstop dike to give residents time to escape should the sea finally reach their doors...
...green Great Wall" of grasses, shrubs and trees 4,350 miles across their northern region. In Peru archaeologists have revived a pre- Columbian agricultural system that involves dividing fields into patterns of alternating canals and ridges. The canals ensure a steady supply of water, and the nitrogen-rich sediment that gathers on their floors provides fertilizer for the crops...
...steep to walk on have been scraped to bare earth. Acreage bulldozed for shopping malls looks like this. Until these ravaged uplands reseed themselves -- which on the steepest slopes simply may not happen -- erosion is inevitable, and the most reliable yield, says Forester Morrison in disgust, will be "sustained sediment" in the streams that drain them. We head eastward to a landing field near Mount Rainier National Park...
...number of ways. Dredging can stir up the bottom, throwing pollutants back into circulation. The U.S. Navy plans to build a port in Puget Sound for the aircraft carrier U.S.S. Nimitz and twelve other ships; the project will require displacement of more than 1 million cu. yds. of sediment, with unknown ecological consequences. Similarly, natural events such as hurricanes can bestir pollutants from the sediment. The estuarine environment also changes when the balance of freshwater and salt water is disturbed. Upstream dams, for example, diminish the flow of freshwater into estuaries; so do droughts. On the other hand, rainstorms...
Buried toxins can also be moved around by shrimp and other creatures that dig into the bottom and spread the substances through digestion and excretion. Though ocean sediment generally accumulates at a rate of about one-half inch - per thousand years, Biogeochemist John Farrington of the University of Massachusetts at Boston cites discoveries of plutonium from thermonuclear test blasts in the 1950s and 1960s located 12 in. to 20 in. deep in ocean sediment. Thus contaminants can conceivably lie undisturbed in the oceans indefinitely -- or resurface at any time...