B11: Hatzic Oxbow Lake EarthCache
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Difficulty:
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Terrain:
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Size: 
(large)
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Hatzic Lake is an abandoned meander of the Fraser River. Now cut
off from the main channel, it is considered an oxbow lake. The
length of the lake, on its north-south axis, is approximately 3.7
km, while Hatzic Island is approximately 2.6km in length, 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.
Neilson Regional Park is right on Hatzic Lake and offers some great
views of the lake from several areas within the park.
1) What is the approximate width of Hatzic Lake at the posted
coordinates?
2) What is a backwater? (answer can be found by reading the cache
page)
2) Hatzic Lake is very shallow, approximately 12 metres at its
deepest point, why do you think the lake could be so shallow?
3) What direction would the water have flowed when this when still
part of the Fraser River?
4) What is the approximate distance between the south end of Hatzic
Lake and the Fraser River?
5) If you want take a photo of yourself with Hatzic Lake in the
background 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 Facts:
In Australia, an oxbow lake is called a billabong.
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://en.wikipedia.org/wiki/Hatzic_Lake
FV
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Treasures
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