The floodwaters that killed 20 people at a remote Arkansas campground last year swelled well above campers' heads and raced through the flood plain at speeds of up to 7.5 miles per hour, the U.S. Geological Survey said in a report released Wednesday.
Walls of water that averaged 7 feet deep in part of the campground scoured the earth below, carrying away tents and boulders and overturning RVs as campers slept.
"You couldn't stand up in it, and it was flowing pretty fast," said Robert Holmes, a national flood specialist who was a co-author of the report about the flood at the Albert Pike Recreation Area in southwest Arkansas.
Seven children and 13 adults from Arkansas, Louisiana and Texas died in the flash flood after a storm system dumped a tremendous amount of rain on the remote valley in the Ouachita Mountains early on June 11, 2010. As much as 4.7 inches of rain fell in three hours in the upper Little Missouri River watershed.
Since there wasn't a gauge to measure the depths and flows of the stream at the campground, the U.S. Geological Survey sent a team of scientists to study what happened. They used high-water markings and the contours of the land to determine depths and speeds of the flood.
About nine miles downstream, at a gauge near Langley, Ark., water was flowing at about 70,800 cubic feet per second during the flood. That's just above the level at which the U.S. Army Corps of Engineers issues small craft advisories on the much larger Arkansas River.
Meanwhile, at Albert Pike, the peak flow for the Little Missouri River was 40,100 cubic feet per second, the report said.
"As narrow as that stream is, that's a lot," said John Robinson, a meteorologist with the National Weather Service office at North Little Rock.
The findings from the U.S.G.S. come after a report by the U.S. Forest Service last year that acknowledged there was no emergency warning system in place at the campground.
At the time, worried forecasters sent warnings four times in a single hour to advise people of the potential for flash flooding. But those warnings, issued in the middle of the night, never reached vacationing families in the remote campground in the floodwaters' path. The camp had no ranger on-site, no cell phone service and no sirens, and deputies at the nearest sheriff's departments were at least an hour's drive away.
After the flood, workers installed a new transmitter so weather-alert radio signals could reach the campground. The U.S. Forest Service also said officers would drive into the campground during bad weather and warn people that the river could flood.
Forest Service spokeswoman C.J. Norvell declined to comment Wednesday because of a lawsuit filed by family members of three of the people killed in the flash flood. The suit claims the government was negligent by leaving the people there in danger.
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