Hay River Oxbow Lake EarthCache
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The oxbow lake located on Vale Island is an abandoned meander of the west channel of the Hay River.
Now cut off from the west channel, it is considered an oxbow lake. The length of the lake, on its north-south axis, is approximately 3.7 km, with the widest parts of the lake off the northern end of the oblong island at about 775 m. The width of the lake inclusive from its extreme west to east is about 2.5 km.
To log this earthcache, you are going to have to e-mail me the answers to the following questions and post the optional photo.
Information for the questions can be found on the cache page, and at the Earth Cache location.
Access to the oxbow lake on Vale Island is along the Oxbow Trail, which is an extension of the Trans-Canada Trail.
1) What is the approximate width of the oxbow lake at the posted coordinates?
2) What is a backwater? (answer can be found by reading the cache page)
3) The oxbow lake is very shallow, approximately 12 metres at its deepest point, why do you think the lake could be so shallow?
4) What direction would the water have flowed when this when still part of the Hay River?
5) Do you see any evidence at the location that the oxbow is slowly being lost to the forces of nature? Please briefly explain your answer whether yes or no.
6) (Mandatory Task) Take a photo of yourself and/or your GPS with the oxbow and submit it when you log the Earth Cache so that others can enjoy.
You do not have to wait for permission to log the Earth Cache, log it after you send me your answers and I will get back to you if there is a problem with your answers.
Formation of an Oxbow Lake
When a river reaches a low-lying plain, often in its final course to the sea or a lake, it will meander widely. An oxbow lake is formed when a river produces a meander (or curve), due to the river eroding the banks. As the river begins to curve, it cuts and erodes into the outside of the curve and deposits sediment on the inside of the curve. This is due to the fact that the stream moves more rapidly on the outside of the curve and more slowly on the inside of the curve. Thus, as the erosion and deposition continues, the curve becomes larger and more circular.
Eventually,the meander becomes very curved, producing a neck where the two portions of the river almost touch. As the river neck becomes very narrow, the river can break through, this produces a new straighter channel and an abandoned meander loop, called a cut-off. For a short time, water flows both around the meander and through the new channel simultaneously.
As water will take the path of least resistance, eventually the river cuts off the backwater completely by filling the openings to the cutoff with sediment as the water flows through the newly formed channel, this results in the formation of an oxbow lake. This process can occur over a time scale from a few years to several decades.
The oxbow lake lasts until it becomes overgrown with weeds and debris, and filled in with soil, as there is no longer current to move sediment and debris along.
Interesting Fact:
It is called an oxbow lake because it is shaped like a yoke that was once used to hitch an ox to a plough.
Information Sources
http://en.wikipedia.org/wiki/Oxbow_lake
http://hayriver.com/pdf/Official-HR-Visitors-Guide.pdf
http://hayriver.com/visitors/attractions/hiking-trails/
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Treasures
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