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The Illinois River Watershed Partnership (“IRWP”) released a September 2021 report on what it describes as a:
. . . multi-year study on streambank erosion in the Illinois River Watershed. . .
The report is titled:
Illinois river and Tributaries: Streambank Erosion sites and Analysis – 2020 Report (“Report”)
The Report was prepared by Natural State Streams LLC for the IRWP.
The Report highlights:
- How streambank erosion is affecting water quality in the region
- Opportunities to address what is described as a growing watershed challenge
The work involved in preparing the Report is stated to have included a streambank erosion inventory to determine erosion potential of streambanks. The study area included 49 river miles of the mainstem and tributaries of the Illinois River. This work was conducted in 2016.
IRWP and its partners are stated to have monitored streambank erosion through multi-year field measurements at 15 sites. They conclude that erosion is projected to contribute 102,822 tons of sediment and 154,233 pounds of phosphorus annually into the watershed. This is stated to represent approximately 54 percent of the overall phosphorus watershed released into the upper Illinois River Watershed.
By way of findings, the Report concludes that streambanks in the Illinois River Watershed have eroded on average 3.88 feet of bank annually.
Streambank erosion is stated to be driven by a combination of factors that include:
- Natural processes
- Change in precipitation
- Urban stormwater runoff
- Deforestation of the riparian corridor
- Construction in the flood plain
- Past attempts to alter the stream channel
- Debris jams
- Gravel deposits for upstream bank erosion
The Report also states that:
. . . Targeting restoration measures that reduce erosion at the most extreme sites could have a measurable positive impact on the watershed.
Conclusions include a need to address primary drivers of streambank erosion by developing:
- More comprehensive stormwater management solutions
- Maintaining generous riparian buffers in both headwaters and downstream
- Restoring buffers such as native deep-rooted vegetation
A link to the Report can be found here.
