Eroding streambanks
Many landowners that own stream or lakeside property a familiar with bank erosion issues. Bank erosion is not only a headache to landowners, resulting in costly land loss, but also has implications on water quality. One common solution to this problem incorporating rock, known as rip-rap, to promote bank stability. In some situations, rip-rap is necessary to protect high-value infrastructure such as bridges and railroads. In many situations, “green” alternatives are available to landowners.
What is bioengineering?
Lewis & Clark CD has long been an advocate for utilizing “green” bioengineering techniques for stream bank stabilization/restoration projects. Rather than using rock riprap to stabilize an eroding streambank, these techniques offer a more natural solution to improving bank stability. Incorporating live vegetation on an eroding bank rather than rock offers a range of benefits to the stream system including: improved fish & wildlife habitat, reduced nutrient pollution, and increased bank “roughness” or its ability to absorb water energy during high flows. In addition, these bioengineering techniques can be cost-effective when compared to rock stabilization methods.
Benefits:
- Roots help naturally stabilize stream bank once established
- Riparian areas (in and around water) provide critical habitat and food source for wildlife and fish
- Riparian vegetation acts a “buffer” that traps sediment and nutrient pollutants from entering a stream corridor
- Vegetated stream banks increase bank “roughness” and absorb water energy during high flows and flooding
- “Green” techniques can be cost-efficient, especially when projects utilize willow cuttings and volunteer labor
Design Considerations:
The design for bioengineering techniques varies depending on site conditions. The Lewis & Clark CD (or your local conservation district) can help you with all aspects of your projects including design, planning, and in some cases funding. In all cases, when working on or around the banks of a perennial stream, permits are required for completion.
Take a look at some of the bioengineering projects Lewis & Clark CD has been involved with in the past:
Projects
Lake Helena
Background: Ice scour and wave action erode multiple feet of Lake Helena shoreline annually, decreasing water quality in lake Helena and resulting in a costly land-loss to landowners. A willow soil lift technique helps protect landowner’s property-line while improving water quality and fish and wildlife habitat.
Lake Helena Bank Restoration Willow Lift-2021 (300 feet)
| Equipment Costs | $6973.00 |
| Materials/Supplies | $2217.00 |
| Total Cost | $9190.00 |
| Cost per foot | $30.63 |
Lake Helena 2021
Lake Helena 2022
Lake Helena Bank Restoration Willow Lift-2022 (620 ft)
Background: After the completion of the 2021 project, multiple landowners along Lake Helena contacted LCCD about completing similar bank restoration projects.
2022 Lake Helena Project Costs
| Equipment Costs | $15,234.25 |
| Materials/Supplies | $5,174.84 |
| Total Cost | $20,409.09 |
| Cost per foot | $32.92 |
| Cost per foot with in-kind and staff time | $52.67 |
Lake Helena March 2022
Lake Helena June 2022
Lake Helena Bank Restoration Project–2023 (330 Feet)
Background: Following the prior year project, the CD was approached by another landowner on the lake who was interested in doing a project.
Equipment Costs (contracted services) $2323.31
Materials/Supplies $2635.40
Project oversight $5611.86
Total Project Cost $10,570.57
Cost per foot $32.03
All costs include in-kind by the Conservation District, and match (cash and in-kind) by landowner and volunteers
Lake Helena March 2023 (before project)
Before, looking west
Before, looking east
Lake Helena May 2023
After, looking west
After, looking east
The following video is a time-lapse of the 2021 project
The following videos show timelapse images of the 2023 Willow Lift project
Spokane Creek
Background: Flooding in 2018 washed out this rancher’s access road and threatened a downstream county bridge that was replaced after flooding in 2003. The willow wall bioengineering technique provides a cost-effective, environmentally-friendly means of protecting the streambank from future erosion.
Willow Wall Streambank Restoration-2022 (275ft)
| Equipment Costs | $10,630.00 |
| Materials/Supplies | $2123.32 |
| Engineering (floodplain permit) | $9,680.87 (follow up survey still to come) |
| Cost per foot without engineering | $46.38 |
| Cost per foot with engineering | $81.58 |
| Cost per foot with in-kind and staff time | $136.40 |
Willow Wall “typical”
Spokane Creek 2018
Spokane Creek 2022
Project overview:
- Bank erosion
| Materials and Equipment Cost List | |
| Item | Cost |
| 3 rolls KoirWrap700 | $ 825.40 |
| 2 rolls C125/lightweight | $ 184.08 |
| 85 heavy duty stakes | $ 83.53 |
| Sisal rope | $ 24.78 |
| 4 50 ft soaker hoses | $ 139.80 |
| 7 2 x12x 16 @ 46.80 | $ 327.60 |
| 1 day of equipment operation | $ 200.00 |
| Total | $ 1,785.19 |
Project Costs:
| Expense | Total |
| Labor & construction | $23,758.58 |
| BioD-Mat, other materials, plants | $18,017.35 |
| Consultant engineering | $15,867.63 |
| Survey | $1530.00 |
| Floodplain permit | $750.00 |
| Total | $59,923.56 |
Bitterroot before
