Friday, 12 April 2013

The Formation of a Meander

Sometimes I find poems helpful for remembering things! So here's one I wrote about meanders, which includes lots of key geographical words you should be using to describe them!

Rivers always take the path of least resistance
Winding round obstacles into the distance
Even in straight channels bars of sediment seem to form
Alternating deep and shallow sections is the norm’
At alternating intervals of 5-7 times the bend*
The bars deposited when low flow conditions tend
Riffles and pools are they names these features go by
Weaving in between then, the thalweg must comply.

Riffles will reduce the river’s efficiency
Slowed by friction the water has no energy
To carry its load, so it drops it right there
Forming what’s known as a slip-off slope or point bar
While the inner bend is built up by deposition
On the outer bend the river’s flowing fast with a mission
The high hydraulic radius in pools is the reason for
Undercutting by abrasion and hydraulic action more.

This process is perpetuated by helicoidal flow
A corkscrew like movement about which you need to know!
This erodes the river cliff of one meander’s outer bend
Depositing downstream in the next one’s inner bend
As these processes continue the meander slowly migrates
Moving both laterally and downstream at a steady rate.

* 5-7 times the width of the channel – I wrote ‘bend’ because width’ didn’t rhyme!

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