A record 341mm of rain fell in just 24 hours at Honister in Cumbria over the 4th and 5th December, setting a new UK rainfall record. It represented an unprecedented level of surface water flooding affecting key communities including Keswick, Cockermouth and Carlisle, as well as Glenridding hit by two events in the same week.
A £38m flood defence scheme was installed in Carlisle just 5 years ago in response to the last major flood event with the promise that it would protect for a “1 in 100 year event”. This benchmark measure, used by the Environment Agency, insurers and the government to determine flood severity, was seized upon by the media to seek answers as to why it happened again in such a short space of time.
No perfect model
But climate change isn’t going to follow a rule book. There is no perfect model given the complexity of our weather patterns and therefore defences will only be fit for what we extremes we have suffered at the time.
Building higher river defences to protect communities is fine, but it only serves to push the problem downstream or funnel and magnify fluvial flooding. Flood plains do their job soaking up what they can, but the water will travel indiscriminately.
The floods demonstrate how precarious our community infrastructure really is. Two electricity sub stations were inundated in Carlisle and Lancaster losing power to 55,000 homes over a 2 day period; landslides scoured river banks throwing trees like missiles into towns further blocking bridges and culverts. 17th Century Pooley Bridge and the main A591 access route were destroyed and the west coast main line cut off, effectively sealing eastern Cumbria off from the outside world.
What can be done?
The Government has promised an additional £50M in flood defences and aid for the area and it is right that more money goes to areas with the greatest population and therefore the greatest need.
But greater investment should now also be made in improved modelling and sustainable flood management. The concept of “rewilding” our upland slopes has been mooted, so that trees act as a natural sponge to stop surface run off cascading down bare slopes into highly receptive rivers.
Also, what do we do about better water management in the lower catchments around population centres – yes, higher defences, but how high do you build before it becomes impractical? You may never see the river again in your town!
We should also consider, where appropriate, much grander schemes for sustainable drainage and storage systems. Understanding the capacity of the subsoil to attenuate the water and directing it more effectively around high risk major population centres needs to be considered within new infrastructure investment decisions.
Lead local flood authorities, working in partnership with the Environment Agency and data partners such as ourselves have a real opportunity now to create a more holistic and sustainable flood management policy, accounting for local conditions, backed by superior science and the latest flood data.