Most rivers initially start by a steady flow of water following the course of least resistance. The water flows where it can and starts to maintain this pattern as the water remains consistent. While the water does what it likes the river bed is subject to natural forces that can manipulate the flow and direction of the water over time. Erosion and the properties of the underlying materials can change the face of a river over the years. Which brings us to this Earthcache: The Etobicoke Creek Meander...For Now
As you wander around GZ you will quickly see that this creek is subject to many such meanders for most of its length. Why? The underlying materials are soft (most of the creek banks are lined with shale) and as the water begins to pummel a certain area it starts to erode. As you will see the rate of flow in the water changes depending on where in the meander it is, this results in removal of material in the "higher speed" zones and deposits of material in the "slower speed" zones. Depending on how closely you look you may get to perceive the change that is occuring in this particular section of Etobicoke Creek.
In this diagram we can see the way in which a meander can change to form an oxbow lake. The arrows represent the direction of the water flow. At first (1) the water proceeds to follow the course of the meander and slowly erosion and flooding continue to change the surrounding creek bed. (2) The movement of materials in the creek bed continue as it begins to deteriorate the width of the neck (or when flooding is a factor it can reduce the height of that area by washing out top soil and other sediment). (3) Once the neck is consumed by the natural process it may still feed the bend of the meander but the flow would be greatly reduced. (4) Before long, sediment begins to fill the openings of the bend (or cutoff) and starts to all but eliminate any real flow from the river into this former component. (5) When enough sediment has come to rest at the openings of the bend, it will no longer be a part of the river and will now be considered an oxbow lake. Separated by the same forces that created it (almost sounds like a geological soap opera).
In order to log this EarthCache you will need to answer a few things based on your observations at GZ. Please email me your answers to these questions and then feel free to log your find:
1. Comparing this meander to the diagram in the description, at what phase would you say this meander is? Please explain.
2. Take a look at the "neck" of the meander, what is the greater factor to its transition: Erosion or Flooding? Please explain.
3. Measures have been taken to maintain the outside wall of the bend, what are they and why are they needed?
This location is great for wildlife, bring your camera you never know what you will see. Have fun, be safe, happy caching!
1.Meanders on Wikipedia
2.Oxbow lakes on Wikipedia
3.Brampton Trail Guide