Bank stabilization is used to enhance a severely or moderately eroding stream bank that is lacking riparian zone vegetation. The KWRC has stabilized over 2500m of eroding stream bank in the Kennebecasis Watershed, greatly reducing the amount of sediment flowing into the rivers.
Benefits of Bank Stabilization:
1. Reduces sediment being introduced into the watercourse.
2. Enhances fish habitat.
3. Maintains the riparian habitat.
4. Preserves topsoil.
5. Reduces greenhouse gas emissions by retaining carbon dioxide in soil.
The KWRC uses three bank stabilization techniques to reduce erosion and prevent sediment and nutrients from being introduced to a watercourse:
A rock toe armor along Ward's Creek one year after installation.
Where urgent bank stabilization is not needed, toe armoring and/or backsloping is a good remedy. Boulders are placed at the waters edge where erosion is occurring and the bank is then sloped back to prevent further soil and sod from sloughing into the stream. This technique is often used in smaller watercourses with slower flow and in areas where natural re-vegetation is more promising and the landowner is agreed to a wider setback. Sediment eventually deposits on and around the boulders as it becomes part of the watercourse. Once planted, back sloped banks become very stable and better suited for high water events as they more readily disperse the waters energy.
For extremely unstable banks, where urgent stabilization is required, heavy blasted rock is used to stabilize the stream banks. Done properly, rock armoring lasts a long time, enabling trees to become well established in the riparian zone behind it.
Crib walls work in much the same way as bank armoring. The big difference between the two techniques is the material used. Crib walls are constructed by stacking and anchoring large logs parallel to an eroding stream bank. The wall created protects the bank from further erosion and allows the riparian zone to regenerate.
A crib wall placed along Parson's Brook