Record flooding partly an act of man, experts say

Some experts believe the record floods in the upper Mississippi River valley are partly the result of the region's farming practices, Joel Achenbach reports in The Washington Post. But it's hard to say just how much, because several factors are in play.

Achanbach's story starts with Kamyar Enshayan, a Cedar Falls city councilman and director of an environmental center at the University of Northern Iowa, who "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."

Jerry DeWitt, director of the Leopold Center for Sustainable Agriculture at Iowa State University, told Achenbach, "I sense that the flooding is not the result of a 500-year event," the designation of the U.S. Army Corps of Engineers. "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."

Also, rivers are filling up with sediment and don't have as much carrying capacity, said Lyle Asell, a special assistant for agriculture and environment with the Iowa Department of Natural Resources. And he reported that in the last year, Iowa farmers withdrew 106,000 acres from the federal Conservation Reserve Program, which had paid them not to cultivate the marginal land. Much of the new plowing was for corn, prices for which are setting records in part because of the demand for ethanol.

Iowa State meterologist Elwynn 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," Achenbach writes. "There has also been speculation that global warming could be a factor." Climate change is one reason that "500-year floods" can occur twice in 15 years. "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." (Read more) For our recent post about stream gauges and real-time from them, click here.

Achenbach is a leading explanatory journalist. He is the author of the 1991 book Why Things Are and the 1996 book Why Things Are and Why Things Aren't, which explain such things as why the Oval Office is oval. He also writes Achenblog.