The Dechannelization of Nippersink Creek: Learning about Native Illinois Streams through Restoration

Abstract

In 1999, McHenry County Conservation District returned 2.5 km of Nippersink Creek to its original meandering course, after the stream had been channelized in 1951. The District graded the banks to an average slope of 7:1, and used coconut fiber matting and large rock to slow bank erosion. Natural Resource Management crews installed over 150,000 wetland plants along the stream edges and lower banks. Using cross-sectional elevation surveys, we followed four years of change in this newly meandered channel. In addition, we investigated the relationship of the modern stream to relict meander scars left in the nearby stream valley. We found that, despite erosion control measures, the stream continues to undercut its banks. Rates of lateral migration are much less than in unaltered sections of stream. Even so, bank erosion remains a problem because the modern stream is entrenched about 60 cm below the relict meanders. As the stream migrates laterally, the tall cut banks collapse into the water, reducing water quality. In response to these findings, McHenry County Conservation District installed two gravel riffles to raise the water level by approximately 60 cm over a 0.8 km reach of the stream.