Meanderings EarthCache

At this EarthCache you are required you to visit the location, make some observations and message or email me the answers. 

If you feel willing and able you could add photos to your log too.

It’s best if you make your observations from the top of the ridge, you don’t actually need to go down to the river at all.

Please be aware that this is sited in a SSSI.

You do not need to leave the path and please do not damage the area.

This EC is all about the different directions a water course can take as it errodes the banks it passes.

You will be asked to read up about meadering streams and how they can make a lake that is not a lake at all.

So read on and thanks for visiting.

A meander, is a bend in a sinuous watercourse or river, they can happen in steep rivers and wide shallow ones. A meander forms when water moving erodes the outer banks and widens its valley, and the inner part of the river has less energy and deposits silt. A stream of any volume may assume a meandering course, alternately eroding sediments from the outside of a bend and depositing them on the inside. This can even happen in fast flowing streams like the one at this location. The result is a snaking pattern as the stream meanders back and forth across its down-valley direction. When a meander gets cut off from the main stream, an oxbow lake forms, this happens when the curve cuts and joins the main flow again. 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, not a problem here.

An oxbow lake isn’t actually a lake at all; An oxbow lake is a U-shaped body of water that forms when a wide meander from the main stem of a river is cut off, creating a free-standing body of water. In a steep V shaped valley like this one and oxbow lake is unlikely because of the amount of material that would be required to be moved is huge. This landform is so named for its distinctive curved shape, resembling the bow pin of an oxbow.

How an oxbow lake forms

The river meanders across the valley; The river erodes laterally (from side to side). The river erodes the outside of the bends and deposits on the inside so its course is changing. This erosion narrows the neck of the meander often during a flood the river will cut through the neck the river continues in the new bed and the meander is abandoned, new deposition seals off the ends and the cut-off becomes an ox-bow lake.

All this requires space and steep valleys are not likely places for oxbows to form. Though there might be in time no Oxbow lakes have formed here just yet.

Questions

1. Describe what you can see, concentrate on the path, flow and directions of the stream below.
2. Do any of the wanderings of this stream do a 180⁰? What is approx. radius of the meanders?
3. Do you think it is likely that an oxbow lake will appear here, how did you come to this conclusion?
4. From your vantage point above, how deep is this little valley?

Thanks for visiting and I look forward to reading your logs.

treboR