Dave Olson, Published May 24 2009
SPECIAL REPORT: The good, the bad, the Red
It’s also about energy.
There’s lots of it in the water that pours into the Red River from hill country to the west and east.
But if fast-moving tributaries like the Otter Tail in Minnesota and the Sheyenne in North Dakota are Interstate on-ramps, the sluggish Red River is a 12-car pileup waiting to happen.
Add to that picture more moisture than the region has seen in recorded history, and epic flooding should be no surprise.
But, somehow, it always is.
And the really scary part: This spring’s flood, which reached a record 40.82 feet in Fargo on March 28, could have been worse.
Experts say if the snow had waited for April to melt in a single rush and if the region had gotten typical April rainfall, predictions that the crest would soar to 43 feet – or higher – might have come true.
But let’s start at the beginning.
Roughly 10,000 thousand years ago, a melting glacier retreated northward, leav-ing behind a fresh-water sea known as Lake Agassiz.
The lake eventually disappeared, revealing a giant billiards table stretching from South Dakota to the Canadian border, which was covered by some of the richest topsoil on earth.
Today, a contrarian river – the Red – flows north across the expanse of that long-extinct lake bottom, as if searching for the glacier that gave it life.
Below the rich topsoil left by Lake Agassiz is another geological legacy – a deep stratum of clay.
It came in handy when communities frantically searched for material to build dikes with, but the clay also contributes to water woes.
“Clay soils do not absorb water quickly,” said Paul Todhunter, professor of geography at University of North Dakota in Grand Forks.
And the moisture that clay absorbs in the fall can create flooding issues in the spring because new water has no place to go, according to Todhunter.
“When a clay soil freezes, it usually has water in it in the fall. They become like concrete. They’re impermeable,” said Todhunter.
Wet, wet, wet
Which leads to another factor in explaining why the region has experienced several major floods in the last 12 years – precipitation.
A wet cycle that began in the 1990s reached a new high between Sept. 1 and March 31, when the Fargo area received 18.93 inches of liquid precipitation.
That swamped the previous record of 14.08 inches set in 1882 and dwarfed the 10.62 inches that fell be-tween Sept. 1 and March 31 in 1996-97, when the region experienced its third largest flood on record.
Any significant rain this past April would have sent rivers to even crazier heights, said Charles Fritz, director of the International Water Institute at North Dakota State University in Fargo.
“If we would have gotten normal rainfall, we would have probably hit some of those numbers they were talking about. We’re lucky we didn’t,” said Fritz, who said the Red River’s topography almost ensures that heavy floods will periodically strike.
The elevation of the Red River drops less than 6 inches per mile from the confluence of the Otter Tail and Bois de Sioux rivers to the mouth of Lake Winnipeg.
That creates a sluggish river and one that is slow to accommodate water from tributaries in times of high water.
“It’s a very low-energy system. It’s just kind of a strange geological setting that sets up these flooding events,” said Fritz.
And for all of the big floods the area has experienced in the past 12 years, Fritz said there may be worse to come.
For proof, he pointed to the past.
“If you look at the floods before we took records, the largest was in 1827,” said Fritz.
“They estimate the flood stage in Fargo was 42.5 feet. That’s kind of the biggie.
“Think of 2009 and add two feet of water. That would be devastating,” added Fritz.
Furnaces in the attic
The latest flood has sparked a renewed push for “permanent” flood protec-tion. But Fritz said such a thing doesn’t exist.
“We can talk about flood-damage reduction, but you can never protect, because there’s always a chance for a larger flood,” said Fritz.
While new flood control measures would help matters, Fritz said no building project will take the place of individuals taking per-sonal charge of their home’s protection.
“We need to better prepare for the next big flood, because it could happen next year,” said Fritz, who added residents of the region already have a variety of defenses to choose from.
“How many homes in Fargo have flood insurance?” said Fritz, adding:
“Why do we allow people to put furnaces and water heaters in the basement? Put ’em in the attic.”
Readers can reach Forum reporter Dave Olson at (701) 241-5555