MANHATTAN, Kan. -- Midwesterners have been paying close attention to the current El Nino, and for good reason. The last El Nino (1992-93) helped create roiling floods that ravaged the Kansas, Missouri, and Mississippi river basins.
For some scientists, however, 1993's legacy isn't lingering worry. The flood still is revealing important new lessons on how to reduce damage and soil loss, and those lessons are spreading. In fact, the Russian Academy of Sciences has just printed study results from K-State Research and Extension.
"We've never had scientific data from flooding on this scale," explained Wayne Geyer, forestry scientist who led the research team with KSU landscape architect Ken Brooks. "The '93 floods went from valley wall to valley wall, rather than riverbank to riverbank. The water flow was so massive that it broke long-known rules of erosion."
Still, Geyer's only surprise was how strongly his new findings confirmed what foresters have long believed. His results also put a new twist on -- and bottom-line reason for -- the riverside tree plantings that environmentalists have been promoting for years.
"It's one thing to say you should go to the expense of planting trees because they'll filter run-off from your town or farm and help keep our water cleaner," Geyer said. "It's another to say trees will keep floods from ruining or taking away miles of expensive levies or $5,000-per-acre bottomland."
The forester said the scale of the 1993 flood made it something historians believe is only likely to occur every 100 to 500 years. Even so, its lessons are more immediate, because the Midwest gets water-related damage every 10 to 15 years. Flooding is part of the weather pattern -- like drought.
In "average" floods, water tends to eat away soil on the outside of curves -- sometimes to the extent of carving out a new channel. At the same time, it deposits silt on inside curves, widening the bank and/or creating sandbars. The water's effect on straightaways depends on what's bank-side.
Geyer found, however, that 1993's effect on a rural three-county stretch of the Kansas River had no tie to whether the water course was straight or curved. Instead, on average:
Geyer studied the Kansas River through U.S. Geological Survey maps, USDA's 1992-93 aerial photographs, and a computer program that can use maps to adjust photos for exact comparisons.
Wherever possible, however, he also made on-site surveys.
This field study confirmed that even in 500-year floods, trees not only hold riverbanks but also protect the land beyond -- much like a giant coffee filter. Trees slow down water as it surges both to and from land and dwellings. They also seine debris, ranging from flood-floated buildings to weed seeds.
"At best, unprotected farms on the Kansas River probably picked up about 6 inches of sand as the flood receded. Soil scientists will tell you that' s tricky to handle without ruining the structure of your land," Geyer said. "But some farms on the Missouri River ended up with 6 feet of sand on beautiful bottomland. Recouping the money farmers have spent dealing with that could take 100 years."
Missouri has a natural resources tax that can help pay for planting streamside "buffer strips." But Kansans also can accomplish a lot at relatively low cost, Geyer said.
The Kansas Forest Service, based in Manhattan, sells tree and shrub seedlings at cost to Kansans who will use them for conservation. Each Kansas county Extension office can provide order forms.
"If your bank isn't 15 feet high, about the easiest way to get started is to take willow cuttings and push them into the muddy ground, 4 feet apart in staggered rows. You'll soon have a living wall that works wonders," Geyer said. "A cedar tree revetment is effective, too, but hard work. You can use old Christmas trees or volunteer cedars, cabling them down. They'll do an amazing job of building up soil.
"Then you can get a quick start above the bank by planting riverbottom trees, such as silver maples, cottonwoods or green ash. If you also let the brush grow, you'll soon have good quail hunting. If you p]ant grass, the strip can become summer and winter protection for grazing livestock or a park."
A woody buffer strip 66 feet wide can protect waterways from 90 percent of the yard and farm pesticides and fertilizers that rain tends to carry into streams and rivers, he said. Plus, it can protect state lands from the next flood -- which may come this year, but quite likely will arrive within the decade.
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