Seeing the standing water in the fields along the valley, it seems incredible that it was only 3 weeks ago that the streams finally joined up to give continuous flow all the way from Mobwell Pond to the Colne. Just two weeks earlier Mobwell Pond was full but no flow out, actual flow began at Missenden Abbey and just reached to Water Hall, Chalfont St Peter springs provided a second surge that disappeared again before the golf course, and the final reach began in Chalfont Park so we had 3 rivers and three dry reaches. Not any more!
Ground water levels are rising quickly with visible change daily, and against the background of the calendar year 2023 having the highest rainfall for at least 30 years, we can expect continuing high levels and wide effects on low lying areas, particularly between Amersham and The Chalfonts. Flooding in the centre of CStPeter last month is a result of sewer overload and surcharging and blocked drains. A 24 hour operation pumping from beside the precinct into tankers is just about containing the situation without resorting to direct pumping into the river as has happened before. Inundation of the meadows reflects the groundwater level: chalk streams do not “break their banks” except where artificially channelled for some reason.
The Misbourne has been in the news recently with much publicity regarding the Gerrards Cross sewage treatment works overflows, though surprisingly less media attention to the drainage flooding in Chalfont St Peter or the overflows from the balancing tanks at Amersham (where the recently installed monitoring system is now reported as “not working”). Chiltern Conservation Board and Chiltern Society magazines have reported on the Save the Misbourne workshop and Affinity Water are about to publish their suggestions for further work to contribute to the initiative.
We feel that a key element must be to resolve the situation between Amersham by-pass and Quarrendon Mill. The bund around the “wetlands” recently created by the partial diversion of the leat to the river’s original course and back again has been substantially overtopped and a large amount of water is rushing down the South Bucks Way eroding a new channel, flooding arable fields and potentially inundating the old Mill grounds. Interestingly the other recent improvement work by Affinity at Amersham, being in the natural water course, allows current high flows to ride over the new berms without flooding into the surrounding area, whereas the berms in the leat at Q Mill have no such freeboard above.
So, as noted, rainfall for the twelve months to end December was the highest since the period to end March 2013 and before that 2001 when heavy rains in February, March and April on top of a similar January figure to now led to significant difficulties in Amersham and the Chalfonts. The amount of rain in the remainder of the recharge period through to April will determine if water levels this year remain just exceptionally high or become a more serious problem.
The first graph below shows the average of all the dip locations along the valley on 1st February 2001, 2014, and 2024 compared with the February average for the past 30 years and also the maximum for any months. As usual, the Misbourne presents some anomalies, but broadly with the exception of Quarrenden Mill and “Old Road” (= Shardeloes access), current values are above 2014 and just below 2001. Put another way, the second graph shows the average of all dips over the whole years 2000/2001, 2013/2014 and 2023/2024 to date. (Similar info for each location will be available on the website very soon).
And a a couple of pictures of what that means:
The Pheasant Hill road bridge at Chalfont St Giles
The “dry area” near Water Hall
The WhatsApp group has been quite lively as flow has reached the parts not normally reached, and some great photos have been shared. If you would like to join, just send me an email.
On the practical front, there are a few spots where litter has accumulated, dead branches have fallen and brambles are snagging debris in the flow, all of which provide us with an excuse for putting our waders on. As examples there is work to be done nearly all the way from the fallen tree at CStPeter tennis courts to the ford in the village, beside the Merlin’s Cave grounds in CStGiles, and at a couple of places in Old Amersham. So, suggested dates for first working parties of 2024 are Saturday morning 24th February and Wednesday afternoon 28th. Please let me know if you can join for either or both and I’ll send details nearer the time. (No doubt, many will use WhatsApp)
We will have a “not-a-meeting” – i.e. a very informal chat and a drink in the Greyhound on Wednesday 21st from 7.15 pm. All very welcome, especially our several new supporters, for general and often rambling discussion of matters fluvial and otherwise and to attempt a little forward planning
Oh, and by the way, by all accounts everyone who attended agrees that the Annual Dinner in December was a great success and excellent value. Greyhound team did us proud. To avoid signing up for a potentially clashing event this year, why not make a note in your diary now for our 2024 dinner which will be on Wednesday 11th December?