Rouge Valley Oxbow - A Work in Progress EarthCache
Hidden : 12/23/2010
Difficulty:
3 out of 5
Terrain:
3 out of 5

Size: Size: not chosen (not chosen)

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Geocache Description:


How to log this cache

Read the content provided in the below cache description, using your GPS navigate to the posed coordinates and provide the following:
1) Using your GPS, provide your current elevation.
2) Using what you have learned in the cache notes, what stage would you say this Oxbow is in? Early stages? Midway?, Full Oxbow?
3) Using your surroundings, provide two examples to support your answer.
4) Navigate to N 43° 52.016 W 079° 15.052 (Ref-1) and using your GPS, provide your current elevation. Using this number and the number provided in question one, how deep is the erosion of the bank where the Oxbow is forming?
5) (Optional) Post a picture of yourself AND\OR your GPS at the caching site and post with your log
6) Have fun! You are geocaching!



What's an Oxbow?

What you are looking at it an Oxbow in the making. Although this is not a full Oxbow formation there are several very prominent features that show the formation.

A Oxbow or meander in general is a bend in a sinuous watercourse. A meander is formed when the moving water in a stream erodes the outer banks and widens its valley. A stream of any volume may assume a meandering course, alternatively eroding sediments from the outside of a bend and depositing them on the inside. The result is a snaking pattern as the stream meanders back and forth across its down-valley axis. When a meander gets cut off from the main stream, an oxbow lake is formed. Over time meanders migrate downstream, sometimes in such a short time as to create civil engineering problems for local municipalities attempting to maintain stable roads and bridges.

Meander formation is a result of natural factors and processes. The waveform configuration of a stream is constantly changing. Once a channel begins to follow a sinusoidal path the amplitude and concavity of the loops increase dramatically due to the effect of helical flow sweeping dense eroded material towards the inside of the bend, and leaving the outside of the bend unprotected and therefore vulnerable to accelerated erosion, forming a positive feedback loop.

Flow of a fluid around a bend is vortex flow in order to conserve angular momentum. The speed of flow on the outside of the bend is fastest, and on the inside of the bend is slowest. The water surface is also super-elevated towards the outside of the bend, so on the floor of the channel the water pressure is greater on the outside of the bend than on the inside of the bend. This pressure gradient drives a cross-current towards the inside of the bend. The cross-current along the floor of the channel is part of the secondary flow and sweeps dense eroded material towards the inside of the bend. The cross-current then rises to the surface near the inside of the bend and, moving near the surface, flows towards the outside of the bend, forming a helical flow. The greater the curvature of the bend, and the faster the flow, the stronger is the cross-current and the stronger the sweeping of dense eroded material along the floor of the channel towards the inside bank.



The question of formation is why streams of any size become sinuous in the first place. There are a number theories, not necessarily mutually exclusive.


This cache was developed by a:



Please note the following:
- DO NOT attempt to access the cache site via the 407. Please use the provided parking coordinates
- Please use extreme caution when navigating and collecting information. DO NOT attempt to scale or climb the areas of erosion along the path. There is no need to do so as there is a path to follow between reference points.
- Please take extra caution if attempting this cache at night.

Additional Hints (No hints available.)



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