The slow, dirty and dangerous flooding of the South Platte River

2013-09-20T08:00:00Z 2013-09-23T17:59:15Z The slow, dirty and dangerous flooding of the South Platte RiverBy PETER SALTER / Lincoln Journal Star JournalStar.com

The Colorado floodwaters pouring into Nebraska are strewn with debris and stained with so many contaminants -- millions of gallons of raw sewage, thousands of gallons of oil, and chemicals from businesses, homes, farms and feedlots.

But two days after the dirty water crossed the state line in the South Platte River, officials here had a clearer picture of what they're dealing with. And just how much.

“The volume of water coming into Nebraska is substantial,” said John Miller of the U.S. Geological Survey, who spent much of Thursday on a bridge near Roscoe, watching the water rise below him.

“The really neat and significant part of this flood is how long it's going to be here. This is not going to come down real quick.”

The volume of water

Earlier this week, Nebraska didn't know what to expect from Colorado.

“The magnitude of flooding could be unprecedented,” Earl Imler of the Nebraska Emergency Management Agency, said Monday. “Many gauges were washed away from bridges in Colorado, so it is hard to predict how much water we will be getting.”

Now they know. The volume of water flowing beneath the bridge near Roscoe -- about 40 miles from the Colorado border -- was expected to reach more than 21,000 cubic feet per second Thursday.

That's about 150,000 gallons flowing by every second. Almost enough to fill an Olympic-sized pool every four seconds.

A cubic foot of water is about the size of a basketball, said Bob Swanson, director of the U.S. Geological Survey in Nebraska. “So that's 20,000 basketballs going by every second. That's kind of what we're talking about.”

And unlike past South Platte surges -- like runoff from heavy rain -- this water will stay high for days, Miller said.

As it rolls downstream, the crest -- the water's highest point -- will maintain for as long as 12 hours. And then it might drop half a foot, but it could keep that level for four days.

This also is record territory. The water moving past Roscoe, for instance, was set to break the 1995 record of 20,100 cubic feet per second.

“The magnitude of this flood is significant,” Miller said.

But as recently as late Wednesday, the river beneath him had been sandy, dormant and dry.

Slow-moving threat

The water's leading edge, maybe a couple of feet deep, appears first, pouring through the empty river channel at just more than a mile per hour.

It reached Keith County late Wednesday, said Randy Fair, county attorney and emergency spokesman.

“There were people out there well into the evening, and there still wasn't any water. The river looked the same as it has for the last six months. It doesn't come in like a wave; I think some people expect a huge tidal wave.”

But it rises rapidly once it arrives, Miller said. At Roscoe, it jumped 8 feet in eight hours. It carried at first a sulfur smell, and he described its sound as laminar -- a flat, smooth-running flow.

It grew turbulent throughout the day, and as its velocity increased, it started carrying foot-tall standing waves.

All of this in a river bed that has been dry for so long.

“It's going to be dramatically different to the people along this stretch of water,” Swanson said.

Where it's going

They have had plenty of time to prepare. Landowners along the river -- mostly farmers and ranchers -- moved livestock, tractors and hay bales to higher ground, said Dan Guenthner, North Platte and Lincoln County emergency management director.

“Everything they can move, they've moved. It's going to flow into cropland, and some have cut their crops,” he said.

A river bank failure near Brule flooded the co-op's fuel yard, turning its propane storage into an island and tipping over fuel tanks. Floodwaters closed a truck stop at Big Springs, Fair said. And one Brule resident evacuated voluntarily, as did two homes downstream in Ogallala.

But so far, Ogallala was staying dry, and officials were spending much of their time worrying about sightseers getting too close to the flooding.

The Nebraska Department of Roads closed the links between Interstate 80 and Brule and Big Springs, and it could close others. Road crews were using excavators to pluck out any uprooted trees that built up against bridges.

The water was headed toward North Platte, where it was expected to crest early Saturday morning at 13.9 feet -- nearly a foot above flood stage.

“We're watching everything we can watch to make sure our preparations are in front of what we need to do,” Guenthner said. “And our community has responded remarkably well.”

He didn't expect mandatory evacuations or major damage in North Platte, although officials built a clay berm around a retirement home and some businesses are stacking sandbags, just in case.

Up and down the river, locals and strangers were trying to protect the smaller towns of Sutherland and Hershey and Maxwell and Brady.

“The volunteers that are showing up to help are incredible,” Guenthner said. “We just can't thank them enough.”

Dirty water

The water has picked up trees and debris and almost everything else in its path. “I’ve seen hundreds of railroad ties, a large gas tank,” Miller said. “In general, anything that is next to the river that isn't tied down is going to float away.”

But health officials are worried about what you can't see. In Colorado, the flood overwhelmed feedlots and city sewage plants, picking up millions of gallons of raw sewage, said Mark Salley of the Colorado State Health Department.

And as of noon Thursday, Colorado officials were tracking 10 spills at oil well sites -- two of them releasing nearly 19,000 gallons of crude into the South Platte.

The flooding also picked up farm, industrial and household chemicals.

Stay away, officials say. “Unless people have to be involved in debris cleanup, we're telling everyone to avoid contact,” Salley said.

The U.S. Geological Survey will sample water in Nebraska, but it could be weeks before results are known, Miller said. And the state Department of Environmental Quality won't test moving water, but it could sample standing water that accumulates in public places, such as reservoirs and parks, spokesman Brian McManus said.

Nebraska health officials were urging landowners downstream from the flood to protect their wells. And emergency officials were urging others to simply stay out of its path.

Like the capsized canoeist who was rescued from the river near Big Springs.

“We did have reports of people trying to do recreational activities in the water, and we're trying to encourage people to say away from the river,” said Jodie Fawl of the Nebraska Emergency Management Agency. “It looks deceptively mellow. But we just really want people to be careful.”

Reach Peter Salter at 402-473-7254 or psalter@journalstar.com.

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