North Dakota residents on tenterhooks, eyeing Red River's rise

The Red River is expected to crest this weekend in North Dakota. But already, some of the region's farmland is under water after smaller rivers, swollen with melting snow, overflowed. (March 19)
Associated Press
Saturday, March 20, 2010

FARGO, N.D. -- A year ago, weather forecasters changed late in the game their estimate of just how high the Red River would rise. That stoked an 11th-hour sandbagging flurry here that proved unnecessary: The new prediction was wrong.

Now, as the Red swells again toward an expected crest Sunday, tens of thousands of Fargo residents are weighing the latest National Weather Service forecasts, well aware that predicting what happens on the river is anything but an exact science.

Forecasters analyze a numbing array of factors when making predictions. Hydrologists use computer models that account for soil moisture, frost depth, snowpack, temperatures, rate of snowmelt and more. Then there are the unknowns, such as how much rain might spill into the river.

All of these play out over thousands of square miles of the Red River Valley.

"I think they do a wonderful job, provided that they're looking into their crystal ball with all the wisdom they have," said Fargo resident Richard Thomas, 61.

On Friday, the Weather Service changed its crest-level prediction again, lowering it a half-foot to 19.5 feet above flood stage Sunday.

Thomas said he's not too worried about flooding, with a home that sits two feet above Sunday's projected crest. A year ago, he weathered a crest of nearly 23 feet above flood stage, thanks to a special water-filled tube. It's on standby if crest predictions go higher this year.

Last year's record high water helped forecasters by giving them new data on how the river behaves at those levels, said Greg Gust, warning coordination meteorologist at the Weather Service in Grand Forks, N.D. That makes the Weather Service more confident this year, he said.

"I wouldn't say we're relaxed," Gust said. "We're more relaxed, or less hectic than other years, and that's simply because the planning process has enabled us to get some more things in place."

Recent history in the Red River Valley has been painful for the Weather Service.

In 1997, forecasters knew there would be record flooding on the Red River, 80 miles north of here, in Grand Forks, but they didn't realize just how bad it would be in time for the city to build up its dikes. The Red swelled to a record 26 feet above flood stage, and the defenses failed, forcing most of the area's 60,000 residents to evacuate.

Last year, after forecasters belatedly increased their crest prediction to 25 feet above flood stage, Fargo raced to pile its sandbags higher. The estimate proved to be about two feet too high, and the dikes held when the Red topped off.

Meteorologists and disaster officials sometimes refer to major floods as "500-year" or "100-year" floods, but many say the terms should be dropped because they're often misunderstood to mean such a flood will occur only once in that time period.

Fargo's second big flood fight in as many years can be largely laid at the feet of El NiƱo, the phenomenon that has affected weather nationwide. In the Upper Midwest, an unusually early warm-up meant rapid snowmelt. And with the ground still frozen, that melted snow moved quickly into streams and rivers.

Gust said forecasters have been getting a better handle since 1997 on how to predict flooding. They have developed better ways of determining the mathematical probabilities of flooding, he said.

Knowing the odds helps people make better dollars-and-cents decisions. Gust pointed to Fargo's decision a few weeks ago to try to stockpile 1 million filled sandbags, which gave the city a head start when a stretch of unusually warm weather accelerated flooding projections.

Thanks to increases in computing power, Gust said, forecasters can run alternative scenarios fairly quickly, something they couldn't do in 1997.

"Every year there's a different wrinkle that shows up on the terrain," he said.

© 2010 The Washington Post Company