Environment in action

Friday morning I made a particular point of looking out for Himalayan balsam while walking to the station. None to be seen, anywhere. I suppose there must have been a local campaign to get rid of it – it is certainly on the Environment Agency’s list of invasive species which ‘upset the balance of the ecosystem.’

Something else is changing our ecosystem however. I started noticing last year the way that mud banks & sand banks were developing in the stream; this year not only are these growing apace, but the beds of the stream, the river & even the culvert are getting noticeably filled with stones – not just pebbles but larger ones, I guess about the size a house brick would be if it were squashed flat.

The river bed has always been well covered with such stones but lower downstream, from the point at which it levels out with very little further to fall before it reaches sea level; the water usually flows quite fast up where we live, leaving any stones little chance to settle.

It seems obvious that this must be a result of all the rain & cold weather, but I am at a loss to work out if the stones are being washed down from higher up (several roads have been closed recently while landslips were repaired), or whether the increased flow is eroding, cutting away at, the rock in the bed of the river.

It is like watching all those diagrams of the history of river basins come alive in real time in front of your eyes.

Links

Himalayan balsam Fact File
Competence of Rivers To Transport Coarse Bedload Material
[PDF] Chapter 6: Downstream fining and rounding of bedload material.
River Basins

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