On the 5th August we began work on the first section of the Phase 2 channel: this is the main channel just to the north of the “Stage Zero” section described in my last post and coloured red in the whole project overview on the link:
For an idea of scale from the top to the bottom of our project, we’re talking about 1.75 km. The line of the original river most likely ran about here or between here and the Stage Zero section to the south marked with the wiggling blue lines. This ditch marks the lowest point in the floodplain, but there is evidence of all sorts of drainage works and floodplain disturbance here … as we dig where we are finding upturned river beds here and there … so it is hard to tell exactly.
For context … downstream, this straightened ditch flows into a more obviously meandering channel, (the orange section) much modified, but now feral and overgrown (which in turn runs back into the main river at the d’stream limit of our project) … and this I’m certain marks the pathway of the original channel. This feral section is part way through an interesting process of self-generated rehabilitation (see the pic below) squeezing through overgrown willows and doesn’t need a hell of a lot doing to it. We will drop some old poplars here and there to create pinch-points and we will replace gravel in the more heavily dredged sections: but mostly this lower reach will be an exercise in letting the river do the work, especially once whole flow of the river is directed at it.
To connect the new channel on the Common (the purple channel in the overview plan) with the lower section of original channel (the orange channel), we needed to improve the ditch (in red) and also make it large enough to take a portion of the flow (some will flow through the Stage Zero section). The work on 220 meters of channel took about eight working days. It wasn’t easy, digging into water and trying to shape banks and a river bed where the gravel was in scant supply. We won gravel here and there by pushing the meanders onto the undamaged, northern bank and we have now built some piles of excess gravel coming out of the next phase which we will bring downstream to build up the riffles in this rehabilitated ditch.
The two pics above were taken in more or less the same place and only a few days apart. The water looks rather muddy at the mo, but that is just old ditchwater and not yet a flowing river. Look carefully and you can see how we have pushed the meander on to the northern bank, under which we found a seam of undamaged gravel, which we then pulled into the foreground to underpin the riffle marked by the post … which still needs a bit more gravel. All the spoil on the northern (right in photo) bank will be graded into the slope once it is dry.
Another before and after, but looking upstream. Again, you can see how we have pushed on to the northern edge. The channel is a little smaller here than upstream as the intention is to push a proportion of the flow through the woods to hold on and enhance the rather lovely habitat that is in there (see previous posts). So this channel is about 4 meters wide, but narrower in places, 70cm deep, with a meander length of approx 25 meters. We have yet to dress it out with LWD. The intention is definitely that the river will do the rest of the work, knocking this channel about a bit with any luck, so that in a year or two it looks authentically natural.