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Initial scientific data shows a man-made flood of the Grand Canyon created dozens of new beaches and filled in backwater channels, replenishing the canyon's environment.

The weeklong flood that began in late March was the government's first attempt to operate the Glen Canyon Dam above the Grand Canyon for environmental purposes. Environmentalists had said for years that the unnatural flows of the Colorado River below the dam were washing away sediment and that beaches were disappearing, along with fish and plants.According to tests done by the U.S. Interior Department, the so-called "habitat-building test flow" created 55 new, large beaches in the Grand Canyon and increased the size of more than half of canyon beaches altogether.

Ten percent of the canyon beaches decreased in size as a result of the flood.

Plant species - many of which are nonnative to the canyon - were distributed as a result of the flood throughout the river and in back channels, the data showed.

The department's Bureau of Reclamation, the government's dam-managing agency, said the tests show the river's esteemed trout fisheries were not hurt by the flood. The trout fishing industry, which sits just below the dam, had been the most vocal in questioning what negative impacts the flood would have.

The so-called flood consisted of opening four giant steel tubes at the base of the dam, sending a thundering torrent down the Colorado and into the canyon.

Additional reports on the flood's impact will be completed in September, with the final analysis coming at the end of the year, the Interior Department said Wednesday.