40,000 CFS Release From Glen Canyon Dam Shows Promise In Rebuilding Grand Canyon Beaches

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At least until this summer's up-and-down hydropower flows eat into them, the new sandbars appear up to the task, scientists on a six-day recon float trip said last week. John Hamill, chief of the U.S. Geological Survey's Grand Canyon Monitoring and Research Center, pointed to a soccer field-sized sandbar where two shirtless kayakers flung a Frisbee. Off to the bar's side was a long stretch of flat water, impounded on three sides. "There's no flow-through, so it really just takes on the temperature of the air," he said. That can mean the difference between 60 degrees and 80 degrees. "That's a beautiful sandbar there," he said.

The flood also could protect archaeological treasures. One hundred-fifty ancient sites including camps, cliff dwellings and potsherds are threatened. Runoff from the canyon's rims chisels into them because there's no sand cover. But at one beach where researchers have placed wind-borne sand gauges that spin like weather vanes, studies of the 2004 flood determined that up to 1 1/2 feet of sand blew uphill to offer a buffer, said Helen Fairley, sociocultural manager at the monitoring center.

Elsewhere last week, including near Grapevine Rapids at the head of the narrow and fast-flowing Granite Gorge, waterborne sand piled up on beaches 12 to 15 vertical feet atop what pre-flood photos showed as boulder fields with no tent sites. Upstream at Cardenas Creek, a beach that had atrophied for years looked sweet to 23-year river guide Zeke Lauck as he floated past. Tamarisks and tufts of tall grass poked through a smooth white plain. Although summer fluctuations will erode some of the gains, Peterson said it shouldn't be as bad as the last time, when the dam churned out up to 20,000 cubic feet per second in the summer. This year the flood will be limited by environmental considerations to 16,000 or 17,000 cubic feet per second.

Peterson and the Park Service's Martin jockeyed for scientific position at each research camp they passed last week. When U.S. Geological Survey research hydrologist Scott Wright told officials that early sampling suggested good sandbar construction, Martin pressed him to say whether frequent floods might be necessary to maintain the gains. "It will take multiple events over many years," he agreed. Peterson, in turn, pointed out that the river didn't deposit sandbars far downstream in 2004 even though researchers found it to be carrying lots of sand there. He said there's much to be learned before the next Interior secretary decides on a flow schedule, and there will be protracted lobbying.

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http://www.sltrib.com/ci_8599903