COON CREEK - About 30 farmers and interested citizens gathered at the Coon Creek Conservation Club for a meeting of the Coon Creek Community Watershed Council on Wednesday, Jan. 5. Those present heard about grant funding and use of grade stabilization structures or small dams for flood control and erosion reduction.
The next meeting of the watershed council will take place on Wednesday, Feb. 2, at the Coon Creek Conservation Club, with dinner at 6 p.m., and the meeting at 7 p.m.
Vernon County Conservationist Ben Wojahn informed the group that they had been funded through the Department of Agriculture, Trade and Consumer Protection (DATCP) Producer-Led Watershed Council grant program for $20,000. Due to increased demand for the grant funding, the council received half of the total $40,000 amount applied for.
“As part of the requirements of the grant, at least one member of the group is required to attend DATCP’s Producer-Led Watershed Council Workshop, planned for February 23 in Rothschild, Wisconsin,” Wojahn explained. “The cover crop conference will be the next day in the same location, and so interested members could consider attending both events.”
Wojahn also reported that the group had received $40,000 from the county’s 2022 Ho-Chunk funding. These funds are intended to help install flood prevention and erosion reduction conservation practices in the Coon Creek Watershed. In that watershed, three flood control dams failed in the August 2018 rain and flooding event, and USDA-NRCS is recommending that the other four be decommissioned in coming years. This means that other flood control measures will need to be adopted in the watershed.
Vernon County Land and Water Technician Matt Albright, and LaCrosse County Conservation Specialist Christina Hesselberg, made presentations to the group about their work in building grade stabilization structures, or ‘small dams.’
Allbright explained that small dams, designed to control somewhere between a 10- and 20-year rain event, help to stop gully erosion, settle out and store suspended solids, improve downstream water quality, reduce peak water flow rate after a storm event, are cost effective, and can also serve as a water source for wildlife in the form of a farm pond.
“The life expectancy of these type of small dams is about 10-20 years before the sediment pool behind the structure fills up and needs to be excavated,” Allbright said. “These type of structures will be more like speed bumps in the types of really big rain events we have been seeing, but will help to control erosion from smaller rain events.”
As far as how these types of structures help to improve surface water quality in watersheds below them, they do so by reducing soil erosion which carries phosphorous into waterways. This is especially true during peak flow periods immediately following a rain event, when the most phosphorous loss occurs. These dams will not help to reduce nitrogen loss from fields.
Allbright said that the structures can be designed either to a 10-year rain event standard, or to control up to a 25-year rain event. The larger the structure, obviously, the greater the cost and the larger the area of a landowner’s property that will need to be devoted to the structure. He said that design considerations include the drainage area controlled by the dam location, the sub-watershed slope, the soils at the dam location, land use above the dam location, the availability and quality of material for constructing the dam, the depth to bedrock at the dam location, and the location’s proximity to karst features such as sinkholes.
Once the dam is completed, the landowner will need to commit to conducting maintenance and repairs of the structure. Maintenance responsibilities include keeping the structure clear of woody vegetation, and inspecting the structure for damage after heavy rain events and ensuring that repairs are made promptly.
“Anytime you build a structure like these, the land use above the structure makes a big difference in how effective they are and in how well they hold up in rain events,” Allbright explained. “Installing conservation practices above the structure such as grass buffer strips can really help to prolong the longevity of a structure.”
Christina Hesselberg also made a presentation to the group on grade stabilization structures. The Coon Creek Watershed is present in three counties – LaCrosse, Vernon and Monroe. Conservation staff from all three counties are active in the watershed council.
Hesselberg showed the groups images of a small dam project recently completed on the farm of Dan Korn. The Korn Dam was one of the three large, PL-566, flood control dams that failed in August of 2018. That dam, like so many, was named for the family whose property the dam was built on. Dan Korn is the chairoerson of the Town of Washington Board in LaCrosse County, and he has been an active participant in meetings held to determine the future of the breached dams.
Hesselberg said that the size of a small dam structure depends on the size of the drainage area to be controlled by the dam, the storage area behind the dam, the storm event the dam is designed to control, the principal spillway type and size, and the auxiliary spillway size.
She explained that the longevity of dams can be strengthened by promoting water infiltration capacity in the watershed above the dam. She listed methods for promoting infiltration such as contour strips, adding hay rotations, grass buffer strips, cover crops, no-till farming, grassed waterways and grassed headlands.
Generally, the cost of building one of these structures ranges between $8,000-$20,000. USDA-NRCS will fund a flat 70 percent of the cost, which works out to be between 50-70 percent of the total cost of the structure. Counties can help to fund these projects, adding to the federal cost share available, with their annual allocations of Soil and Water Resource Management grants.
Bob Micheel, Monroe County Conservationist, reached after the meeting, remembered a different time when the funding available was different.“Back in the days of the Kickapoo Watershed Project, the DNR would fund projects like grade stabilization structures at a flat 70 percent, and then we could use federal cost-share dollars to get the funding up to as much as 90 percent,” Micheel explained. “When you get to 90 percent cost share, the landowners really start to want to participate.”