My partner Jennifer and I worked on segment 9 of the Don riverbank in Glendon, York University (as seen on map above) to see what river stabilization have been used and possible improvements. It was a sunny day with some wind and the temperature being around 7 ° C. Our segment started on the light green camera and is the first picture shown below.
We found there was less vegetation closer to the river but more further away and that there was little wildlife evidence (i.e. lack of animals such as squirrels, birds) which could be from lack of stability of the riverbank. We did not see much stabilizing methods being practiced on most of our river section. There had been some evidence of previous stabilizing on one end of the river but this was mainly due to stabilizing a bridge that was built there. However the stabilizing around the bridge was limited and already reduced from time since it was only rocks used and nothing to reinforce it. We looked at a two different techniques that could be implemented in order to better help stabilize the river and prevent erosion.
The need to stabilize rivers is high since river erosion can cause a loss of vegetation and habitat for organisms that live around the surrounding area (Severson et al. 2009). A common river stabilizing technique is using rocks against the river walls. Some may use large boulders to prevent erosion since they are less likely to move and are more stable. Using only smaller rocks is not the solution since as time passes the rocks will move and fall to the base of the river. There is also a technique known as gabion baskets. These are essentially the same idea as the wire nets but more efficient. They are wire rectangular baskets that rocks, sand and soil, or concrete rubble can be placed into in order to stabilize the wall and can be stacked on top of each other (Thompson et al 2016). For erosion control, cage rip rap or use of rocks is preferred since it takes longer to disintegrate. Another technique we researched for river stabilization is willow spiling. It consists of using live willow rods woven together and placed against the desired area to stabilize and prevent erosion of rivers. This technique is not as widely used in the USA and Canada but more in the UK and other European countries (Anstead and Boar 2010). They are a natural and cost efficient way of stabilizing rivers but cannot adjust to all locations. Since it is a live plant, it requires a lot of sunlight to grow and work as a stabilizer. After a while, the willow grows a dense top growth like a bush and a complex root system in the soil. This helps to reinforce the soil and prevent it from eroding.
Based on the different stabilizing techniques we researched and what we saw on our part of the river, using gabion baskets would be the best technique. We found that rocks are already being implemented for their use in stabilizing the river but not necessarily to their full potential. Gabion baskets are more reliable as the rocks can’t move within the baskets and do not disintegrate at a fast pace. We would not recommend the use of willow spiling since it requires a large amount of sunlight to survive. Segment 9 of the river had very little sunlight due to the large amount of canopy coverage preventing the sunlight from coming through. It is not commonly used and will need frequent maintenance and thus not efficient for Glendon to use. This is why Gabion baskets would make the most logical choice for the restoration of the Don river.
Anstead , L and Boar R.R. 2010. Willow spiling: review of streambank stabilisation projects in the UK. Freshwater Reviews. 3(1):33-47.
Severson, J. P, Nawrot, JR, Eichholz, MW . 2009. Shoreline stabilization using riprap breakwaters on a Midwestern reservoir. Lake and Reservoir Management. 25(2): 208-216.
Thompson, D. M , Puklin L.S, Marshall, A.E. 2016. The long-term impact of channel stabilization using gabion structures on Zealand River, New Hampshire. Ecological Engineering. 95: 779–792.