What is in this article?:
- The two-stage design has perforated tile lines that empty field water through side inlets in the ditch at a more stable place
- This is a low-tech, common-sense approach
- The slope of a two-stage ditch is one-half to two-thirds of a conventional ditch
Kevin Willibey’s ditch copied Mother Nature; her floodplains, that is.
His drainage ditch used to flood over its banks after big rains, loosen its soil, and the banks would collapse into the ditch. The northeastern Indiana grower, along with engineers and the Nature Conservancy, has tested a new ditch design with more gradual sloping sides that mimic a natural floodplain (see related gallery).
This new gold standard in drainage ditches has evolved over 10 years. As ditch water spendsmore time in contact with rocks, vegetation and native grasses on ditch banks, nutrients and sediment adhere to vegetation instead of flowing downstream. The changes in the floodplain provide optimum environment for micro-organisms that do the denitrification.
“This removes the amount of sediment and nutrients contaminating watersheds, and ultimately, the Gulf of Mexico,” says University of Minnesota Bioproducts and Biosystems Engineer Bruce Wilson. “These are very popular in Ohio. There are several in Michigan and Indiana; and there are two or three in Minnesota.”
The two-stage ditch design is more stable, he says. “One cause of conventional ditch failure is water flow impinging on the toe of ditch banks and seepage forces through bank walls. The two-stage design has perforated tile lines that empty field waterthrough side inlets in the ditch at a more stable place.”
Wilson collaborated on a two-stage ditch project near Adams in southern Minnesota, along with the Minnesota Pollution Control Agency and the Mower County Soil and Water Conservation Board. It was funded by an EQIP grant and private donations from Cargill, General Mills and others.