Sunday, 19 May 2013

Build It and They Will Come —  The Benefits of Clarity (Pt1)

Now that Summer has finally arrived and the Sowe, my local river, has fallen back to normal summer levels, the water has cleared and I can now appreciate the scale of change wrought by the endless winter spates and floods.

Raging continuously for nigh on three months, the river burst its banks three times during that period, was full to the brim the rest and fell very slowly even when the rains had abated due to the surrounding land being so utterly saturated by them. Witnessing torrents of water crashing through was awe inspiring then, not because the river is large and impressive, it's actually very small, but because the sheer power of flood waters are a spectacle to behold and a force that demands respect no matter how insignificant a channel they flow through.

The astonishing duration of those immense powers exerted upon a small structure I'd put in the river the previous summer I thought would have created something interesting in effect. What I failed to appreciate then was that the changes it had made to the stream would not only be more impressive than I could ever have imagined, but also life giving.

As they subside, the changes effected by torrents once as high as the topmost trails of accumulated rubbish,  start to become apparent — though only in Summertime would they be fully appreciated...

There's a small immature willow growing out the bank below a cascade weir to where I lugged a load of heavy rubble in the form of stones, boulders and bricks and threw it all underneath the trailing branches creating a small tapering diagonal groyne reaching half way across. The floods brought organic material downstream in abundance, branches, sticks, twigs, reeds, weed stems and all kinds of litter, plugging the gaps and causing the sapling and groyne to become a solid but permeable permanent structure...

Come Summertime the flow reduced, the water cleared and finally I could see bottom. The shallow glide above the tree narrows into a channel now and below is a deep enough pool for fish to live in, but who would ever know this remarkable feature created over just one winter was actually a happy collaboration between man and nature?

However, without the groyne this would never have happened because the trailing branches simply weren't large enough or strong enough wrapped in rubbish to hold much water back before they caved in, and just weren't low enough to make much difference where it really matters anyhow, which is at the level of the riverbed.

I failed to record the original thinking little would happen, but this is the scale of the stone block groyne placed beneath the willow. Insignificant in size, perhaps, but it turned out be hugely transforming ... 
The solid heavy material placed beneath not only helped plug the space between but also deflected the current and reduced the sheer weight of water pressure on the sapling which happily collected what must be half a ton of saturated debris, an obstruction that today looks as if it were created entirely by natural processes — the pool scoured below as if it had been there for centuries.

Of course, in wintertime I couldn't easily appreciate just how substantial the pool created by the floods really was because I couldn't see bottom, but now that levels have dropped and the water clarified I can, and it is remarkable. Before it was no more than a foot deep and my dogs would paddled about in it, but they swim around in it now because it's over three feet deep!

Where it had been a shallow and overly broad channel running straight through under the sapling, now  with powerful flow to one side dissipating into a placid swirling back eddy it had become a feature complex and diverse in flow structure, and in times of heavy water a refuge. I fancied it provided the best potential home for fish in miles because it's precisely a mile and half downstream where I know from long experience of this little stream that the first large fish are to be found, but here in this forlorn place they were entirely absent and for good reason, as we shall see...

As the waters fell the riffle became visible for the first time...

Well, the power of the water raging continuously for months on end had scoured more than just one pool. It had gouged out what must be ten tons of gravel from below the willow and deposited it as a central bank twenty yards downstream where the water passed over and began once again to shift material further downstream, scouring another longer but shallower pool and depositing the load as another remarkable feature at its terminus — what I can only describe a 'transverse' riffle.

Only when it had become fully exposed did a rapid narrow channel begin to form against the bank at bottom right — the river seeming to want to resume its meandering nature there

I wonder what will become of this in time ?
This is a pile of gravel that now blocks the river almost bank to bank when the water is low but allows water to fall out to one side in a narrow rapid channel where it flows straight into the bank and is now in process of gradually undercutting it. Of course the river is creating a meander and in time that exposed gravel will become a bed that plants will colonise completely (they're already starting to!) and eventually become semi-solid land except in flood when it will submerge.

What has been created in total is a transformed length of watercourse of sixty or seventy yards length that is to all intents and purposes a totally different stretch of river than it was this time last year. Below the transverse riffle the effects of the floods peter out and the river returns to what it was — a shallow and overly broad man-made channel with little flow diversity and no place fit for fish life, but above is a complex series of features that I just know provides just the right kind of home for them...

But, would they ever come live in it?

To be continued...

The pool.

A lovely looking 'new build' now — but will it be seen as fit to inhabit?


  1. Apparently a fish ladder has been put in at the pub in Baginton, that can only help your cause

    Somebody somewhere must have realised that certain species of fish need to travel upstream to shallows to spawn and, not only that, but also to consider the fish important enough to then invest in the principle!

    Great. The future looks good

  2. I heard they were putting fish passes into the weir at Stoneleigh too, George. That would mean trout making their way up stream because there's a population below it, and eels too.