Misbourne River Action update from Bob Older - December 2020

Dear All

At this time in the past twelve years we would have been finalising plans for Misbourne River Action’s annual Christmas dinner, but that is another casualty of 2020. So too was the majority of our work programme with only two (very productive) work parties completed. However, there is lots of river news - some of it good…………….but not all!

Most of you will have seen the disastrous effects of the early HS2 activities up the valley with construction of the depot and tunnel portal at Denham, preparation for vent shafts at Chalfont St Peter, Chalfont St Giles, Amersham and more at Little & Gt Missenden. Our hearts go out particularly to the residents of Bottom House Farm Lane whose plight you may have read about in the national press and seen on TV. in 2016, these same residents bravely presented the case to the House of Lords Select Committee for an alternative access to the Chalfont St Giles Vent Shaft over to a relatively easy access point on the A355. This would have avoided all the damage to a very special length of the valley, their and other resident’s environment, disruption of the local rural businesses, delays on the busy A413, and avoided the need for work in the river (see photo) but this was contemptuously dismissed. In the event, the initial HS2 proposal for the lane didn’t work and the amended version is far worse than envisaged at the time.

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HS2 “temporary bridge” construction - Bottom House Farm Lane.

That contemptuous dismissal echoes the treatment given to our own presentation to the Committee alongside the group SaveStGiles which expressed the concern, supported by the most eminent chalk aquifer experts, that tunnelling at a relatively shallow depth under the river at Chalfont St Giles and elsewhere poses a risk of damage to the river and potential loss of flow. One of our slides happened to show the willow tree beside the pond in Chalfont St Giles and I will always remember one of the Lords Committee observing that “everyone knows how much water willow trees need and if you were to cut down the trees along the river, you might not have these problems”. I kid you not! Our proposal was that the EA would require HS2 to line the river, in an environmentally approved manner, for 500m or so over the tunnel at the crossing point. I believe it is not too late for this fairly minor risk mitigation to be incorporated into the planning for the tunnelling operation and will be campaigning for it to be reconsidered and hope for support from as many influential parties as possible.

Another project, to provide a parallel pipeline to the existing from Chalfont St Giles pumping station to the Amersham treatment works as an insurance against problems with the existing one due to HS2 tunnelling, has been completed. Meanwhile a project to provide turbidity removal at Amersham Treatment Works is underway - again against the risk that the tunnelling operations will cause turbidity from the disturbance of the chalk within the aquifer.

So, enough about HS2. There has been yet another project going on in the Amersham area and that is the diversion of the river away from an old but artificial “leat”, or channel, back towards its natural course for a few hundred metres downstream of Amersham By-pass. For various reasons, it was not possible to develop a route for the whole of the reach to Quarrendon Mill so the new diversion loops back into the leat again. Readers may recall that we have in the past been very sceptical about the value of this project and concerned that the new loose bedded channel may well provide a path for greater leakage than the “sealed” bed of the leat. I think the jury is still out on that one though, clearly, with ground water levels as high as they are at present (i.e. unusually high) the reverse could be the case and this be a gaining reach - studies continue. Meanwhile, the current rapid flow over a gravelly bottom at the top of the project and the potential for biodiverstity in the slower, inundated areas towards the bottom have some attraction and it is to be hoped that the opportunity for the creation of an attractive, natural, amenity area will be taken.

New River Diversion downstream of Amersham By-pass

Perhaps partly because of our absence, the Riverside Walk in Chalfont St Giles is in a very sorry state. But good news! The Parish Council are teaming up with TCV (The Conservation Volunteers) to have a “green gym” volunteer programme, initially to concentrate on this stretch. MRA are already members of the TCV organisation and the plan is that we and they and other recruits will commence work on a date to be announced towards the end of January. Assuming all goes well, particularly with regard to amassing a pool of volunteers, other areas may follow. More details to follow after Christmas.

It will be great to be able to benefit from TCV’s young and professional leadership. After 13 years since we launched MRA, we founder members probably have to admit that it is just a little bit more difficult to set up our work parties, clear up afterwards, dispose of the rubbish, and wash all the kit than we found it at the beginning. It would be really good if someone slightly more vigorous than I am these days could, at least, take on the storage of our equipment and its deployment on work days. I daresay we can carry on washing HiVis, gloves etc and the “admin”. It’s also been great to receive a steady flow of new contacts and to hear of some who have been actively improving the river environment - even simple litter picking - withIn their own “bubbles”.

“It’s been a strange year” has become a catch phrase. And so it has for flow in the river. Not surprisingly, groundwater levels have been, and are, above average for the time of year. There was good flow through Chalfont St Peter for several months but all fed by the local springs: flow coming down from Chalfont St Giles only joined up with the top of this “lower winterbourne” for a few days and the end of flow from the upper section rapidly retreated back to Chalfont St Giles where it has stayed. Its progress back down the valley towards St Peter, in the last month has been noticeably slow. Comparison of 2020’s groundwater levels and rainfalls with previous years would have suggested continuous flow for most, if not all, of the year. Very strange, though possibly some indication that the absence of our work parties has had an effect. Note how flow did not continue after the spring at Cherry Acre - unlike apparently similar GWL situations in 2001,2 3; 2010,11; and 2013/4,5,6,7.

Why didn’t flow continue after the peak this year? (or in 1994?)

Flow in the upper reaches beyond Amersham has been much as one might expect from the past year’s rainfall record and groundwater levels. Mobwell Pond has water but not yet enough to spill over into flow down to Great Missenden. Springs downstream of Missenden Abbey are active again and there has been a good stream at Little Missenden. Much more detail available on our website where I keep trying to keep the data up to date.

In other news, “chalk-streams” and the plight thereof have been getting a lot of publicity and attention in both Parliament and in events such as particularly The Chiltern Society Chalk Stream Summit - click on the link here for more info and the video.

Well that’s a long and varied update. All that remains is to wish you and yours Peace and as much Joy as possible this Christmas time, and to look forward to your continued support in 2021 which will hopefully be brighter for everyone.

Yours

Bob

Bob Older
Tel: 01753 885131
Mob: 0781 651 4868
e-mail: bob.older@me.com

http://www.misbourneriveraction.org

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