At this location (photo above) on Douglas Lake, ice push and the power of wave action at high water levels can be devastating to near-shore banks and trees. The photo, taken from an adjoining property, shows our client’s property in the background. It includes the rocky area and a portion of the heavily eroded, bare bank. Note also the many uprooted and fallen trees, just a fraction of those lost over years of damage.
The steep bank on our client’s site has been shaped by years of ice push events despite a previous effort to stop the erosion. Roughly 20 years ago, rip rap stones were installed over landscape cloth. This photo illustrates three problems with the previous installation:
- First, using landscape cloth interfered with the establishment of plants that would otherwise grow between the stones and help stabilize the shoreline. Plant roots cannot readily penetrate the plastic material. The plants we use have deep, fibrous roots.
- Second, the rocks were installed at too steep a slope, so instead of sliding up and onto them, ice pushed INTO the bank, destabilizing the entire structure.
- Third, given the property’s orientation and the distance the wind travels across the open lake, the rocks used were too small for the expected waves. After the rocks were disturbed by the ice push, storm-driven waves washed many of them out into the lake, along with the newly exposed soils. The upper bank was then undercut, and the erosion worsened.
To address all three issues, our North By Nature team applied the current best practices in biotechnical and natural shoreline protection.
First, we removed as much of the old landscape cloth as possible. This will allow the owner to plant a selection of native shoreline plants into the rip rap where they will form a strong web of roots. These plants, along with the existing trees, will seed more native shoreline plants into the rip rap. Over time they will vegetate the upper bank.
Second, the finished slope of the bank is engineered to be shallow enough to direct both expanding ice formations and windblown ice up and onto the protected shoreline instead of into the face of the bank.
And finally, the stones were sized to remain in place even when three-foot waves batter the shoreline for days on end.
Visit the Shoreline Erosion Control gallery on our Photos page for before and after photos a few of our other shoreline projects.