Carrying on from Rivers Week – Day One with Volunteers. I had deliberately staggered the two Rivers Week volunteer days, keeping a day between them to do some work between the two days with the excavator and tree felling without causing any issues with insurance whilst the volunteers weren’t around:
At the bottom of the fields is a small stand of Willow trees. Over time and through lack of management this had resulted in lots of very tall, thin, top heavy Willow trees vying for light, Several of these had cracked and become windblown trees (look in the background of the photo below) and one large dangerous hung-up windblown tree (which I had already dealt with). These Willows weren’t going to waste – as part of the improvements I had consent to install several items of Large Woody debris into the newly narrowed channel to provide some variation in flow, cover / habitat for fish and sort and scour of the gravels.
With very Large Woody Debris, I prefer to use timber which is one to one-and-a-half times the width of the channel, and which is anchored by means of keying it back into the bank with a T-Bar anchor (see photo above), in addition to wooden stakes and fencing wire to wire it down in the wet channel. I could write a complete blog entry on the best ways to install Woody debris, but as the Wild Trout Trust Chalkstream Habitat Manual has already surpassed anything I could write, there is no need! The sites of the Woody Debris installation had already been marked, so it was simply a case of using the narrow digging bucket on the excavator to create the anchor trenches, lift the Woody Debris items into them, and backfill again. This generally reduces the risk of the erosion and the risk of the Woody Debris becoming loose and moving downstream. One of the downsides to this method of installation is that it requires access for an excavator. One of the jobs for the volunteers the next day was to install the stakes and wire in the channel to hold the Woody Debris down, as I was happy to leave it secured purely on the T-bar bank anchor overnight.
I installed three of these items in total, one just downstream of the footbridge, one in an area of over-wide channel (which would be narrowed with the use of a smaller excavator in the near future, and one just above where some of the new gravel was going to be installed.
I also had to backfill and grade the area of eroded and undercut bank where the faggots and stakes had been installed (a task that had involved much blood, sweat and tears the day before), and where some new gravel was going to be installed with the excavator. A lot of this area was unstable due to undercut banks (in places well over a metre of bank was in stubborn defiance of gravity, resting on nothing but thin air, supported by luck and a prayer). In part, this was one of the reasons I was using (in comparison to the size of the channel), such a large excavator. This meant I could sit well back from the edge, use the arm (now fitted with a 70″ grading bucket) at almost full reach to push the bank and existing vegetation down to make the new bank edge, and then safely track closer to the new channel edge to grade it. All without any risk of the excavator turning dirty side up in the channel avec moi in the cab!
Talking of installing gravel…I had fifteen cubic metre bags of 40mm gravel rejects delivered at the start of the week to be installed by the volunteers to supplement the (rather poor) existing spawning areas. This gravel had to be moved across the estate with the excavator and a 6t 4WD dumper (which was invaluable in terms of moving gravel, spoil and equipment through and along the river). Nine bags were moved across the footpath by the dumper, and somehow I squeezed the 13t excavator under the trees and through the gates to lift them into the weir pool channel (on top of the existing riffle which had been cleaned by the volunteers). The remaining six were staggered down the newly graded / narrowed channel, where the flow velocity had increased as a result of the narrowing. Hopefully this increase in flow velocity will ensure the gravel stays clean to allow spawning both this season and in the future. I had deliberately left the new banks uneven and natural looking, rather than having the same angle and grading all the way along the length.
The final big job of the day involved taking something out of the river, as opposed to putting something back in it! This was a sunken boat which had obviously been resident in the river channel for some time, and the bow of which was just visible at low flows. With assistance from a very willing, but anonymous assistant, I did my best to get the boat (which was considerably bigger than I’d estimated at around 15 feet) on the bank in one piece. Sadly this wasn’t going to happen, and it being constructed of fibreglass rather than steel or aluminium, it broke apart as I tried to lift it with the excavator.
If anyone would like a 15ft long jigsaw puzzle, please contact me and you would be more than welcome to it!
From memory, I was still working at 2030 that evening, clearing the excess spoil from the bank grading, and alternating between driving the dumper and operating the excavator to drop the bags of gravel as close to the new bank edge as possible before calling it a day and retiring to bed to try and muster some energy for the volunteers the next day.
To be continued,