Iowa Flooding Could Be An Act of Man, Experts Say
By Joel Achenbach
Washington Post Staff Writer
Thursday, June 19, 2008; A01
As the Cedar River rose higher and higher, and as he stacked sandbags
along the levee protecting downtown Cedar Falls, Kamyar Enshayan, a
college professor and City Council member, kept asking himself the same
question: "What is going on?"
The river would eventually rise six feet higher than any flood on
record. Farther downstream, in Cedar Rapids, the river would break the
record by more than 11 feet.
Enshayan, director of an environmental center at the University of
Northern Iowa, suspects that this natural disaster wasn't really all
that natural. He points out that the heavy rains fell on a landscape
radically reengineered by humans. Plowed fields have replaced tallgrass
prairies. Fields have been meticulously drained with underground pipes.
Streams and creeks have been straightened. Most of the wetlands are
gone. Flood plains have been filled and developed.
"We've done numerous things to the landscape that took away these
water-absorbing functions," he said. "Agriculture must respect the
limits of nature."
Officials are still trying to understand all the factors that
contributed to Iowa's flooding, and not everyone has the same suspicions
as Enshayan. For them, the cause was obvious: It rained buckets and
buckets for days on end. They say the changes in land use were lesser
factors in what was really just a case of meteorological bad luck.
But some Iowans who study the environment suspect that changes in the
land, both recently and over the past century or so, have made Iowa's
terrain not only highly profitable but also highly vulnerable to
flooding. They know it's a hard case to prove, but they hope to get
Iowans thinking about how to reduce the chances of a repeat calamity.
"I sense that the flooding is not the result of a 500-year event," said
Jerry DeWitt, director of the Leopold Center for Sustainable Agriculture
at Iowa State University. "We're farming closer to creeks, farming
closer to rivers. Without adequate buffer strips, the water moves
rapidly from the field directly to the surface water."
Corn alone will cover more than a third of the state's land surface this
year. The ethanol boom that began two years ago encouraged still more
cultivation.
Between 2007 and 2008, farmers took 106,000 acres of Iowa land out of
the Conservation Reserve Program, which pays farmers to keep farmland
uncultivated, according to Lyle Asell, a special assistant for
agriculture and environment with the state's Department of Natural
Resources (DNR). That land, if left untouched, probably would have been
covered with perennial grasses with deep roots that help absorb water.
The basic hydrology of Iowa has been changed since the coming of the
plow. By the early 20th century, farmers had installed drainage pipes
under the surface to lower the water table and keep water from pooling
in what otherwise could be valuable farmland. More of this drainage
"tiling" has been added in recent years. The direct effect is that water
moves quickly from the farmland to the streams and rivers.
"We've lost 90 percent of our wetlands," said Mary Skopec, who monitors
water quality for the Iowa DNR.
Crop rotation may also play a subtle role in the flooding. Farmers who
may have once grown a number of crops are now likely to stick to just
corn and soybeans -- annual plants that don't put down deep roots.
Another potential factor: sediment. "We're actually seeing rivers
filling up with sediment, so the capacity of the rivers has changed,"
Asell said. He said that in the 1980s and 1990s, Iowa led the nation in
flood damage year after year.
This landscape wasn't ready for the kind of deluge that hit Iowa in May
and early June. Central and eastern portions of the state received 15
inches of rain. That came on top of previous rains that had left the
soil saturated. Worse, the rain came at the tail end of an unusually
cool spring. Farmers had delayed planting their crops. The deluge struck
a nearly naked landscape of small plants and black dirt.
"With that volume of rain, you're going to have flooding. There's just
no way around it," said Donna Dubberke, a meteorologist with the
National Weather Service in the Quad Cities. "This is not just because
someone put in a parking lot."
The rising Mississippi River is expected to peak this week, threatening
towns and farmland north of St. Louis as floodwaters continue to move
down the river. So far, flooding and severe weather have killed at least
24 people in three states and injured 106, forced the evacuations of
about 40,000, and driven corn prices to record highs.
Two levees burst just north of Quincy, Ill., yesterday morning, forcing
the evacuation of the small town of Meyer. Yesterday afternoon, Illinois
Gov. Rod Blagojevich (D) visited the town after viewing the nearby Sny
Island Levee, about 12 miles downstream from Quincy and, at 54 miles
long, the second-biggest levee on the Mississippi.
In Iowa, the National Weather Service has reported record flooding at 12
locations on four rivers, including the Cedar, the Iowa, the
Wapsipinicon and the Mississippi. The U.S. Geological Survey has
preliminary data showing 500-year floods on the Cedar, the Shell Rock,
the Upper Iowa and the Nodaway.
The Great Flood of 2008 has, for many inhabitants of sandbagged Iowa,
come awfully soon after the Great Flood of 1993. Or, as Elwynn Taylor, a
meteorologist at Iowa State University, put it: "Why should we have two
500-year floods within 15 years?"
Taylor attributes the flooding in recent years to cyclical climate
change: The entire Midwest, he says, has been in a wet cycle for the
past 30 years.
There has also been speculation that global warming could be a factor.
"Something in the system has changed," said Pete Kollasch, a
remote-sensing analyst with the Iowa DNR. "The only thing I can point my
finger at is global warming, but there's no proof of that."
Jeri Neal, a program leader for ecological systems and research at Iowa
State's Leopold Center, said all these things have a cumulative effect
on the landscape: "It doesn't have the resilience built into it that you
need to withstand disturbances in the system."
The idea of a 500-year flood can be confusing. Hydrologists use the term
to indicate a flooding event that they believe has a 0.2 percent chance
-- 1 in 500 -- of happening in any given year in a specific location. A
100-year flood has a 1 in 100 chance of happening, and so on. Such
estimates are based on many years of data collection, in some cases
going back a century or more.
But the database can be spotty. Robert Holmes, national flood
coordinator with the U.S. Geological Survey, said a lack of funding
since 1999 has forced his agency to discontinue hundreds of stream
gauges across the country. "It's not sexy to fund stream flow gauges,"
he said.
What's certain is that a lot of water had nowhere to go when the sky
opened over Iowa this spring. Some rivers did things they'd never done
before. The flood stage at Cedar Rapids, for example, is 12 feet. The
previous record flood happened in 1929, when the Cedar hit 20 feet. This
year the Cedar hit 20 feet and kept rising. Experts predicted it would
crest at 22 feet, and then upped the estimate to 24 feet. The river had
other ideas. At mid-morning last Friday, it finally crested at 31.3 feet.
The entire downtown was flooded and a railroad bridge collapsed, dumping
rail cars filled with rock into the river.
"Cities routinely build in the flood plain," Enshayan said. "That's not
an act of God; that's an act of City Council."
Staff writer Kari Lydersen contributed to this report from Quincy, Ill.
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