Conservation damage calculated from May storm in Mitchell County
By Jean Caspers-Simmet
Date Modified: 07/16/2013 3:22 PM
OSAGE, Iowa —Rains May 19 to 20 in Mitchell County caused considerable erosion, according to a report by Kurt Hoeft, district conservationist with the Natural Resources Conservation Service in Howard and Mitchell counties.
Rainfall totals on 130,000 acres of Mitchell County ranged from 5 to 10 inches. The heaviest rainfall, 9 to 10 inches, occurred in the Stacyville area in north central Mitchell County.
An inventory of the erosion damage from the storm was competed by NRCS staff.
Hoeft's report said that staff found existing conservation practices functioned as planned, had little sign of erosion and adequately protected soil. Some practices may require maintenance to remove silt. New practices will require more extensive measures.
The staff found that 40 percent of the affected area, or 50,000 acres, wasn't spring tilled, no-tilled or planted to oats and hay and had little visual signs of soil erosion.
Preliminary estimates found 80,000 acres with signs of erosion.
There were 1,000 acres with very severe erosion of greater than 100 tons of soil loss, the report said. Most of it was gully erosion along rivers and streams and where water crossed roadways. The number will go up once the water recedes and a better inventory of damage along stream corridors is completed.
There were about 6,000 acres of severe erosion of 20 tons to 30 tons per acre of soil loss, which were mostly areas where landowners and operators needed to install grassed waterways. The report estimated that 30 percent of the farms had evidence of this type of erosion.
Moderate erosion of 10 tons to 20 tons per acre of soil loss was seen on 32,000 acres consisting of sheet and rill erosion on unprotected cropped fields.
Minimal erosion of 5 tons to 10 tons per acre soil loss was seen on 41,000 acres consisting of sheet erosion.
Repair of conservation practices affected by the storm, which will require earth work equipment that can't be completed by normal farm equipment includes waterway and terrace repair of blowouts, sediment removal, washouts along edges and seeding estimated at $170,000, Hoeft's report said. Gully repairs, rock riprap and sediment removal on damaged lands was estimated at $205,000. The report calculated nutrient losses from excessive soil erosion leaving farms at $240,000. Pasture fence infrastructure that will need to be repaired or replaced was estimated at $10,000.