Soil bioengineering (also referred to as streambank bioengineering) consists of shoreline stabilization and restoration using living plant material (e.g., willow cuttings) and biodegradable geotextiles (e.g., coconut coir fibre mats). This is in contrast to traditional hard-engineered approaches to stabilizing shoreline erosion through the use of materials such as concrete, steel and stone “rip rap.”
Address the underlying cause. Reducing streambank erosion first requires dealing with the upstream causes of the erosion problem.
Manage stormwater at the source. In the short-term, the use of detention ponds, stormwater wetlands and/or bioinfiltration basins and swales upstream from urban watercourses can help to hold large volumes of water during storm events and to slowly release it to adjacent streams at a flow rate and volume that downstream water bodies can accommodate. These upstream stormwater management ponds/wetlands/bioinfiltration basins can also help to improve water quality in the receiving water bodies by giving the suspended sediments time to settle out of the water column. Stormwater wetlands (link) can also help pre-treat stormwater if they are designed for that purpose.
Urban retrofits. In addition to site-specific shoreline and streambank bioengineering there are several indirect, urban retrofits that can also help reduce streambank erosion, there are many urban retrofits that can help reduce streambank erosion by reducing stormwater runoff and promote groundwater infiltration, Many of these examples of NBS are included in this Guide, including the following:
- Green Roofs and Walls
- Stream Daylighting
- Bioinfiltration and Bioswales
- Rain Gardens
Streambank restoration. Once the causes of streambank erosion have been addressed and water is entering the stream at a slower volume and rate, streambank restoration practices can be applied. Many municipalities and stewardship groups are beginning to discover the benefits of bioengineering to protect and restore eroded streambanks. Soil bioengineering involves the use of living plant materials (especially woody vegetation) to stabilize and to revegetate degraded sections of shorelines and stream banks.
Bioengineering for streambank and/or slope stabilization. Several bioengineering techniques are available depending on the site conditions, climate, available materials and resources. For example, willow wands (cut stakes of live willow plants) are commonly used to quickly establish willow plants along streambanks. Multiple willow stakes can be woven together to form a live erosion control device known as a wattle fence. Wattle fences can also be established across gullies or eroded channels to reduce runoff. Brush layering is a technique that involves setting layers of willow stakes into a slope. This is a useful technique to establish continuous vegetation cover on severely eroded slopes. Geo-textile materials such as coir (coconut fibre) can be used in combination with plant stakes in order to stabilize soils while plant roots become established. These materials eventually biodegrade and add organic matter to the soil.
Natural shoreline erosion. It is important for municipalities to keep in mind that some amount of streambank erosion is natural, especially on meandering streams that have developed their shape from patterns of erosion on the outer banks and deposition on the inner banks. It is helpful to get a professional assessment of the eroded bank to determine whether it is occurring naturally or whether it is accelerated due to human activities in the watershed.
Address the cause. Consider the need to address causes of erosion before bioengineering is applied.
Permits. Bioengineering and all other work near water requires permits from Alberta Environment and Parks and Fisheries and Oceans Canada (DFO) before doing any collection work and installing stakes or vegetation near the water.
Plant selection should be based on what species are already growing in the area under similar site conditions (i.e., light, moisture). For example, willows tend to do better when planted near water because they can tolerate flooding, whereas red osier dogwood should be planted upslope in a drier location. Pioneering plant species (e.g., willow and poplar) will establish more quickly and establish conditions needed for future succession of more mature species.
More detailed information on plant harvesting, storage, site preparation, and planting is available by contacting DFO or Cows and Fish in Alberta.
The Business Side
From an economic perspective, protecting and restoring shorelines, banks and slopes helps ensure that valuable public or private property and infrastructure is not lost to erosion. Although soil bioengineering can be labour intensive, it may be more effective and therefore less expensive in the long term. In fact, an example of this type of NBS was completed in Grande Prairie by Aquaterra along the Wapiti River at a cost of $30,000 versus the $1,000,000 cost of utilizing hard engineering solutions at the site. As such, soil bioengineering can be a cost-effective solution for municipalities facing erosion issues.
The Nature Side
There are numerous environmental benefits associated with stabilizing and restoring previously eroded streambanks through soil bioengineering.
Wildlife habitat and biodiversity can be greatly improved by stabilizing streambanks and restoring riparian vegetation. Shorelines and riparian areas provide valuable habitat for many of Alberta’s species at risk. Restoring networks of healthy riparian vegetation allows for better wildlife movement across large areas and can better support populations of species that require continuous habitat.
Aquatic ecosystem health is also improved by the implementation of this NBS. Improving streambank stability prevents sediments from washing into the stream. This will prevent the infilling of deeper areas of a stream, thereby ensuring the provision of deeper, cooler pools of water that are essential habitat for many cold water fish species. Decreasing levels of suspended sediments in the water can also benefit fish by providing the clear water necessary for many of their food sources (e.g., aquatic invertebrates) and providing cleaner water that will not clog their gills. Furthermore, stabilizing the streambank will help prevent the stream from getting wider and will therefore help ensure that riparian vegetation can shade more of the water surface and keep the water temperatures more habitable for fish.
Water quality improvements can also be achieved by stabilizing and restoring shoreline vegetation. Healthy riparian vegetation helps to keep water cooler, thereby increasing the amount of dissolved oxygen it can contain. Healthy streambank vegetation and microbial activity also helps to filter contaminants such as excess nutrients from fertilizers, suspended sediments and other pollutants.
Carbon sequestration that results from the reestablishment of vegetation along streambanks is another ecosystem service provided by this example of NBS.
The Community Side
Continuous networks of healthy riparian areas can be integrated with path networks and used for passive recreation. By reinforcing streambanks, municipalities also increase the safety of recreational areas in the vicinity. Protecting slopes and banks from erosion through soil bioengineering can protect properties nearby and increase property values through the addition of green space. There are numerous health benefits to increased green space and vegetation in communities as well.
 &  Alberta Riparian Habitat Management Society & Fisheries and Oceans Canada. 2007. Growing Restoration – Natural Fixes to Fortify Streambanks. Cows and Fish.
 Andersen, K. 2021. Interview with Land Stewardship Centre. Additional information available online at https://www.aquatera.ca/transparency-growth/wapiti-river-bank-stabilization
Alberta Riparian Habitat Management Society (now Cows and Fish) & Fisheries and Oceans Canada. 2007. Growing Restoration – Natural Fixes to Fortify Streambanks. Cows and Fish.
Andersen, K. (Associated Engineering). January 15, 2021. Interview with Land Stewardship Centre. Additional information available online at: https://www.aquatera.ca/transparency-growth/wapiti-river-bank-stabilization.
Primeau, S., Bell, M., Riopel, M., Ewaschuk, E., & Doell, D. 2009. Green Communities Guide: Tools to Help Restore Ecological Processes in Alberta’s Built Environments. Land Stewardship Centre of Canada.