Apologies for being a day late on the normal schedule. Travelling up to the north of England and seeing the level of flooding close to places like Tewksbury and Worcester was quite staggering; as bad as I’ve seen it over several decades. Our own water levels are high, the peak this week was at 99.76 metres AOD. That’s 3 cm (about an inch in old money) short of the peak in 2014 and well below the levels in 2000 for which we don’t have data. Over the last couple of days, the water level has peaked and fallen back to 99.73 metres AOD, which is a start, but we have a long way to go before we are out of the woods. Several properties are having problems with their septic tanks and soakaways and at least one has a pump running to move excess water to where it can do less damage.
You will notice that in 2014, it took until the end of March for water levels to drop back into the “normal” range, so a rapid fall may not be likely. For those of you who weren’t in the village back in 2014, these pictures of Church Street give an idea of what that extra 3cm of water in the borehole meant within the village.
We’ve said several times that the River Till and our aquifer are unusual and another example of this is when is comes to major flood events. A scientific paper (https://www.waterpowermagazine.com/features/featureestimating-extreme-floods/) published a few years ago looked at major flood events in the Till Valley and the probability of them recurring. In with all the science was a nice table that showed how often we might expect a significant flood event.
The worst flood on record was in 1841 with significant loss of life and property damage. Bankfull discharge is the point the River Till gets to just before it breaks its banks and floods into the meadows. etc. The graph shows that we could expect a similar flood every 300-400 years. However, remember this is a numbers game and all based on statistics. Over many thousands of years, the average superflood would occur at roughly 300-400 year intervals. So whilst the next one might be “due “in 2141, it could happen tomorrow, or not for another 10,000 years! It’s tempting to think that the 2014 flood was two 50-year cycles away from the 2015 flood. But in 1915, Salisbury Cathedral was flooded and rowing boats were photographed in Fisherton Street, so it seems the 2014 flood and the current flood are quite modest ones; closer to bankfull discharge than even the 2015 flood. Take a look here if you are interested: https://www.warmuseum.ca/ke/_resources/5406811/20120179-007.pdf
The other point to note about this graph is the line labelled “FEH”. This is the line predicted for flood frequency by the Flood Estimation Handbook, used by the Environment Agency and others for planning and modelling. The slope of the line is very different to the reality of the River Till and over-predicts the return period for serious floods by at least a factor of 3. The Environment Agency models for triggering flood alerts and warnings probably make use of the same data and so are potentially flawed from the outset. This software was produced for them by a company called Fujitsu that has been in the news quite recently in relation to other software it has produced for the Post Office. The Environment Agency software was roundly criticised for being inaccurate in an article in the Guardian back in April last year: https://www.theguardian.com/environment/2023/apr/04/englands-automated-flood-warning-system-to-stay-despite-inaccuracy-warnings
On the positive side, it looks as if we have another dry week to come, though the following week does seem to hold the possibility of wet weather. Longer term, there remains the prospect of a spell of cold wet weather but drier weather may start to prevail by mid February. Fingers crossed for that.
Contains public sector information licensed under the Open Government Licence v3.0.