Sediment & Phosphorus Reductions through Streambank Stabilization

The banks of the Lower Konkapot Creek, located near the City of Kaukauna, are highly susceptible to bank erosion.  This erosion is caused by many factors, including increased runoff, a decrease in shoreline vegetation, slopes and soil types.  The Fox-Wolf Watershed Alliance and its Great Lakes Restoration Initiative(GLRI) partners are utilizing GLRI funding as well as funding from local sources to stabilize streambanks in an effort to reduce sedimentation and nutrient loading to the creek and ultimately, the Fox River.

Outagamie County Land Conservation staff has surveyed the streambanks along this section of Konkapot Creek.  Staff was successfully in locating and assessing severely eroded streambanks, where stabilization efforts could reduce the amount of sediment lost to creek action.  Additionally, phosphorus, which binds itself to sediment particles, would also be reduced.  Phosphorus is a nutrient that, when found in excess, can cause algal blooms.

This past fall, three streambank stabilization projects were completed along the Konkapot Creek near the Konkapot Creek recreation trail.  If you have utilized the walking trail in the past couple of months, you may have noticed our work.  We would like to highlight these projects here.

Project 1:
Outagamie County Land Conservation, the City of Kaukauna, and a local landowner worked together on this site. The city was growing concerned with the severe erosion occurring near the Konkapot Creek recreation trail and the landowner was concerned with the degrading streambanks on his property.

Project 2:

Here, a local landowner had been growing increasingly concerned with a section of Konkapot Creek that is located on his property. High velocities and large fluctuating water flows had caused the banks in this section of the stream to develop unstable characteristics in many locations, is leading to high erosion. The erosion was undercutting the banks, decreasing stability and eventually causing the ground above to slough off.  These actions were moving the bend closer and closer to the landowner’s home and reducing the size of his yard. After about 5 years of owning the land, the owner indicated that he had lost over 10 horizontal feet in some areas of the bend. Looking through historic pictures of where the stream used to flow and applying some math, it was determined that over 350 tons of sediment had been lost in just one section of the most eroded areas of his property. This is equivalent to almost 500 dump truck loads of sediment lost!

Project 3:

Collaboration between Outagamie County Land Conservation, the City of Kaukauna, and a local landowner also occurred here. The city was concerned with the severe erosion happening along the trail as the undercutting in some areas was almost under the trail itself. The landowner was concerned with the eroding banks on his property as well. A plan was developed that would prevent further erosion and protect the areas that already been severely eroded.
In order to prevent further erosion from happening, an integrated streambank protection design plan was developed. The plan consisted of streambank shaping, rocking, and seeding. Slope shaping was utilized to pull back and stabilize the banks at a 2:1 or flatter slope. Along the outside bends where the erosion was the most severe due to high water velocities, 24 inches of DOT Extra Heavy rock riprap was placed on the graded slopes. A layer of gravel filter material was installed between the rock riprap and the newly shaped streambanks in order to prevent water from seeping in to the pores between the rocks and pulling out the soil. A cover crop of oats was put down in order to establish some immediate vegetation to help prevent short term erosion. While the cover crop is great to protect from short term erosion, a native slope stabilization mix will be seeded in the spring in order to establish a strong deep rooting plant system to hold the banks together and prevent erosion in the long term. A biodegradable erosion matting was also installed above the rock riprap and along the shaped sections without rock riprap in order to prevent erosion before the vegetation is established. The installation of these integrated bank system should help with the erosion problem that these landowners have been facing.

Outagamie County and City of Kaukauna are continuing their efforts to work with riparian landowners along Konkapot Creek and hope to see several more projects installed in the coming year.

Content and Photos were submitted by Wesley Kotila, Conservation Technician with the Outagamie County Land Conservation Department.

2017-12-19T12:09:35+00:00

2 Comments

  1. JOHN HEINOWSKI December 21, 2017 at 10:19 am - Reply

    thanks for solving problems in regards to water clarity, the banks look natural and serve a very needed cause in that the erosion is hopefully eliminated.Here in Madison, there is a super need to stop run off pollution to the lake system, we could use WES HERE TOO.

  2. Diane Hoffmann Kotila December 21, 2017 at 12:43 pm - Reply

    The work looks outstanding. I am excited about the erosion prevention plantings, something for the bees and butterflies benefit too.

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