On Sunday, November 27, 2016, I set off to go survey my section of Glendon to see the river bank and the erosion damage that has been done due to weathering. I worked with my partner Ron to survey the landscape and document it. Below you could see a picture of the path we took to get to our designated segment 10 and the picture below shows the starting point and ending point for the segment that was documented. We were unable to go the full distance due to large fallen tree’s blocking our path. Only the westward direction was documented (our backs to the school). Photos were taken in increments of roughly 5 steps then one photo. See photo’s on my partner’s blog (Will insert link once uploaded)
We went to Glendon when most of the tree’s leaves fell, so the imagery is not as good as the lush green picture above. You could see a sample picture that was taken from the image below.
One thing that was evident when first looking at the photo is the tree’s on the other side of the river are angled as if they are about to fall in.
This is because the root system of the tree was weakened by external forces, such as the river bank. Roots have two main support functions for the tree, to support the vertical weight of the tree and to maintain the stability of the tree so that it does not topple over. Generally, a leaning tree would lean due to the availability of sunlight and therefore the roots will accommodate such needs, however for the tree’s in the photo we could see that they are all straight and that the root system is failing. (“Leaning Tree”, 2012).
The cause of this could be for a number of reasons the river might wash away soil surrounding the tree or the river could wash the nutrients around the tree which would cause the tree to slowly die. Below you could see an image of a tree at Glendon that has fully fallen over. It is hard to tell, but you could see the roots sticking vertically holding the surrounding soil while the tree trunk is horizontal making it a dangerous bridge connecting both sides of the river.
Another thing that is evident when you get close to the river is the steep slope of the river bank on the opposite side. This can be due to two reasons, the bend in the river erosion or river bank failure. Our segment in the river was in a bend which might explain the steep slopes of the riverbanks. This is because in a bend in the river on the outside bend it would have the most erosion levels which would cause steep slopes and shallow slopes on the inside bend due to deposition (“Where do erosion and deposition occur on a river”, n.d.). Another explanation for this occurrence is a river bank mass failure, in which the gravitational weight of the river bank can no longer be supported, which causes it to slip into the river (“River Bank Erosion”, n.d.).
How do we stop this erosion?
Along our journey to take pictures we came across one part in our river segment where large rocks were placed. These rocks seem to prevent a majority of the erosion that was affecting the rest of the river, which could be seen below. The tree’s on the other side of the river were relatively vertical and the bank slope was very shallow, almost at the water’s level.
Although river bank erosion is a natural process, it causes destructive damages to human infrastructure. The river at Glendon, for example, is located right beside two trails which are used on a regular basis and housing property nearby. The way we could help prevent or slow down the rate of river bank erosion is by placing riprap (similar to the stones in the picture above, but on a grander scale) or gabions (a form of netting) along the bank (“More Than Just a Pile of Rocks…”, 2014).
There is proof that soil erosion prevention techniques actually work. In Winnipeg, soil erosion has caused trees to fall over and large amounts of soil have eroded away, collapsing the river sides in sections where prevention techniques were not carried out. In sections where techniques were used the residents were quoted as saying “It is working. We haven’t had any further loss of bank” (“MetroNews, 2016).
Picture of me, with “safety” equipment surveying the landscape. Also, video of the stretch of river assigned was taken, it is not the best quality, but gives you a rough idea of the geological landscape of the small section of the river.
By – Shesan Govindasamy
Leaning Trees – What’s up with that? (2012, January 18). Retrieved December 4, 2016, from Georgia Forestry Commission, http://www.gfc.state.ga.us/community-forests/ask-the-arborist/leaningtrees-whatsupwiththat.pdf
More than just a pile of rocks.. (2014, April 10). Retrieved December 4, 2016, from Soil Erosion and Hydroseeding, http://soilerosiononline.com/article-permalink-8.html
Mulroy. Where do erosion and deposition occur along a river? Retrieved December 4, 2016, from Mr. Mulroy’s Earth Science, http://peter-mulroy.squarespace.com/new-page/
River bank erosion. Retrieved December 4, 2016, from Erosion Pollutions, GEI Works, http://www.erosionpollution.com/river-bank-erosion.html
Winnipeg is in a costly battle against erosion and riverbank failure (2016, October 15). MetroNews. Retrieved from http://www.metronews.ca/news/canada/2016/10/15/winnipeg-is-in-a-costly-battle-against-erosion-and-riverbank-failure.html