Meandering rivers or streams often develop a horseshoe-shaped curve known as an oxbow. When natural erosion or humans cut a more direct path, the oxbow becomes isolated from the river's flow.
Restoring an oxbow does not reconnect it to the river's flow. Instead it's an excavation technique that removes sediment and provides several environmental benefits.
Between 2012 and 2014, Sand County Foundation partnered with several organizations to show how restoring oxbows in central Iowa's Boone River watershed could improve the environment while creating economic benefits for farmers.
Tests planned and funded by Sand County Foundation looked at how restoration of an oxbow can limit the impact of nitrogen runoff from farms. Water temperatures and the fish species present were also examined.
A restored oxbow provides habitat for certain amphibians that prefer slow-moving water. It also provides flood storage capacity.
The benefits of restoring oxbows were many. As more groundwater flowed in, nitrate levels decreased, oxygen levels increased and fish species began to diversify.
Another added bonus was that the mucky material removed from the bottom of oxbows is an organic-rich soil that can be spread on farm fields.
LESSONS LEARNED -- Voluntary, low-cost removal of sediments from these former stream beds is good for the environment and farm productivity. Farmers can cooperate with conservation agencies, organizations and fishing groups to enhance waterways.
Research on the water quality and impacts to fisheries of oxbow restorations in the Boone River watershed continues. We encourage landowners and organizations elsewhere to consider the benefits of oxbow restoration.
Sand County Foundation was proud to be part of this effort with participating farmers, Iowa Soybean Association, U.S. Fish and Wildlife Service, The Nature Conservancy, U.S. Department of Agriculture Natural Resources Conservation Service, and Iowa Department of Natural Resources.
For more on this topic, the Journal of Soil and Water Conservation highlighted the ecological value of oxbows (and the benefits of restoring them) with an article was authored by staff from Sand County Foundation and the Iowa Soybean Association.