Flooding - unpredictable but inevitable
10th December 2015
When I left University in the early 80’s I was looking for a role in environmental management, a role that focussed on working sympathetically with nature rather than trying to confront it and control it - too much of the thinking to that point had been on trying to bully rivers, the sea or the landscape and to force them to do what we wanted. Inevitably the law of unforeseen consequences come charging over the hill, defences were undermined and failed, erosion and flooding resulted and in real terms we’d simply made the situation worse. Sadly such roles did not exist then in the UK and has anything really changed?
All of this thinking came flooding (sic) back this weekend with the news that large area of North Cumbria in particular had suffered badly. This only 10 years after the last such event in Carlisle and 6 years after the tragic floods in West Cumbria around the Workington area in late 2009.
Inevitably over the past few days everyone’s been blaming everyone else claiming that their own actions cannot possibly be at the root of these problems - but the problems need to be addressed so let’s examine a few issues
The Lake District has a unique topography - effectively it’s a large dome with a number of steep and steep-sided short valleys radiating out from the centre, effectively the spokes on a wheel. Therefore any location around the Lake District is at risk from a rapid rise in river levels as evidenced by the Workington floods and those in the Maryport area this weekend. Carlisle is slightly different in that it is built on the River Eden with its source in the Pennines but is also fed by a number of smaller rivers originating in the north and east of the Lake District - hence is at risk from rainfall in two locations.
Living within the confines of the Lake District of course brings its own problems as seen by the unfortunate village of Glenridding at the foot of a steep valley running off the east slopes of Helvellyn - now flooded twice within the last few days. The flooding in Threlkeld and Keswick are linked as they share much of the same ‘improved’ river channel - it does beg the question ‘how successful was this improvement?’
Despite what some may claim (our previous Environment Secretary unbelievably being one notable denier) the global climate is changing. There is however a major difference between (global) climate and (national) weather and as yet no-one can be absolutely clear what impact the warming global climate will have on the UK weather. One model predicts that changes in the thermohaline circulation will result in the Gulf Stream/North Atlantic Drift being significantly reduced and in that case we could see a significant reduction in temperatures in the UK and a move to weather more typical of our Northern latitude. That remains speculative at this stage but it is clear we have seen more extreme and localised weather events, extremes of temperature, extreme winds and extreme rainfall in recent years. There is no reason to suggest that this trend will not continue.
In November 2009, when Workington was hit so badly, rainfall of 316mm over a 24 hour period was recorded at Seathwaite, the figure last weekend recorded at the nearby Honister Pass was 341mm in 24 hours. However the record rainfall at Honister in no way contributed to any of the flooding in the Eden valley, being in a completely separate drainage basin. So Environment Minister, and local MP, Rory Stewart’s statement that ‘this is an extreme and unprecedented event’ while strictly correct does suggest the events were unpredictable and a one-off - this is far from the case and presents neither himself nor his Government in a good light.
Perhaps he should have talked with his boss Liz Truss MP, the current Environment Secretary, before he made such a statement. She now accepts that extreme weather such as we saw was “consistent with the trends we’re seeing in terms of climate change” and that DEFRA would ensure its models were fit for purpose in the light of the events we now increasingly see. One of her more sensible recent statements as long as these models are not solely constructed on the basis of past events and are actively used to determine future policy.
The upland environment
Too much of our uplands are denuded of natural vegetation with plants grazed to within an inch of their lives. As many have pointed out there is little soil up there on which anything else could grow and that is true in many locations - but that doesn't mean to say there never was soil there in the past! The Lake District, other than on the highest tops, was covered in native woodland which served to anchor the soil in place. Sadly that woodland is now long gone as part of the drive towards land ‘improvement’ …. as has the soil!
Upland areas generate heavy rainfall and in the UK that’s a climate-given with the majority of the higher ground being found on the west coast. Heavy rainfall washes the exposed topsoil away, creates gullies, further erodes the landscapes and carries silt away in streams and rivers dropping it into lakes and ultimately the sea. For an illustration of this look no further than any of our estuaries, the silt in the Solway Firth hasn’t always been there, it came from somewhere!
So why does the current farming approach make the problem worse?
- grazing animals strip vegetation down to ground level, leaving a poor and marginal structure with the plants no longer able to hold the soil together
- with a thin vegetation and soil cover there is little or no capacity for soaking up and storing heavy rain - in certain areas exposed bedrock makes the problem all too easy to see
- what little soil there is is trampled and compacted by animals, vehicles and human footfall so heavy rainfall has nowhere to go other than flowing across the surface - ‘overland flow’
All of these taken together mean that the land cannot absorb heavy rainfall and runoff into gullies, streams and rivers is rapid. Once this process starts it’s unstoppable - the less water the ground can absorb the more quickly it runs away, the more it runs away the more it erodes and transports the soil cover away, the less soil cover the less rain it can absorb therefore more is shed into streams etc.
Simply having bushes, trees and a deep layer of grass in a landscape makes a huge difference as their roots both break up and stabilise the soil structure making it easier for rainwater to percolate as well as ‘consuming’ water themselves. Most of us just need to look at our gardens at home to prove this fact - in periods of heavy rain which is squelchier, a lawn or a flower bed?
Now this is not ‘having a pop’ at farmers - I live in a farming community and recognise they have a tough job in the current economic climate but it does feel as though we’re at the point where something has to change.
The biggest ‘sponge’ in the UK is the peat bog - today only a small fraction remains in its natural state, the majority having been drained for forestry or agriculture or extracted for use in horticulture. The image below shows the land above Nant-y-Moch reservoir in Mid-Wales, an environment now no use for anything - yes this was once a peat bog but sadly is not unique across the UK.
A number of organisations are now actively looking to change the landscape back to its previous state, ‘rewetting’ through the blocking of ditches and ensuring that it can absorb more water releasing it slowly over time thus mitigating the impacts of severe rainfall.
One such organisation is Montgomeryshire Wildlife Trust (MWT) through its Pumlumon Project in Mid-Wales - while this is small-scale it does illustrate an alternative approach and more details can be found here http://www.montwt.co.uk/what-we-do/living-landscapes/pumlumon-project.
I hate that term - it implies we have the power to control rivers, we don’t, they cannot be controlled. Too much emphasis has been on clearing and straightening channels, dredging where deemed necessary and constructing long runs of flood banks where flooding occurs. But all of these conspire to make the problem worse. Water flows quicker as it’s not held back by natural obstacles or meanders, faster flowing water is more difficult to ‘manage’ and therefore has more of an impact when floods inevitably occur. Faster flowing water means more of it can reach a particular point in a given time, so if it has nowhere to go flooding is inevitable and with raised flood banks once they are breached the water is more difficult to remove. It’s also worth remembering that flooding is a natural process and will continue to happen as long as we have water on this planet - that’s why the river creates floodplains!
In a location such as Carlisle the coast at Rockcliffe is only 5 or so miles away so raised sea levels have a damming effect on river flow. Where you have a strong westerly winds and a narrowing estuary such as the Solway Firth, sea levels can be temporarily raised and river water simply has nowhere to go. This is of course before we factor in any sea level rise as a result of increasing global temperatures.
I suspect the natural inclination will be to build higher flood defences - a short-term solution that makes the situation worse, look no further than the flooding on the Somerset Levels last year. Focus continues to be on trying to control this 'wall of water' downstream rather that trying to stop it forming in the first place. This is seriously flawed thinking, continues to waste valuable public resources and simply creates problems for the future.
As I child I remember the floods in Carlisle in the 60’s and 70’s and the construction of the first defences - following the 2005 floods, which cost insurers £272m, new defences were commissioned at a cost of around £38m and these were designed to cope with a 1 in 200 year flood. Well it didn’t take long for these to be found out did it and the cost of the recent flooding is likely to surpass that in 2005 with some estimates suggesting the county-wide cost could exceed £500m. What level of cost does it take before someone says enough is enough and rethinks strategy?
For information the Environment Agency’s strategy for the Eden Valley can be found at https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/289422/Eden_Catchment_Flood_Management_Plan.pdf - it makes an entertaining read and in my view is far too narrowly focussed
It’s reasonable to argue that no one factor was alone responsible for the flooding in Cumbria, but the ‘perfect storm’ of high rainfall, rapid runoff, fast river flow and the damming effect of high winds at the coast made it inevitable. However rather than blaming external factors or going into full ‘Ostrich mode’ as many commentators have sadly done this week, everyone should realise the simple logic that explains why the floods occurred - they are by nature unpredictable but most certainly not unforeseeable and are wholly inevitable. So what needs to change?
- Accept that our current strategies are outdated, no longer fit for purpose and will prove increasingly less so
- Start planning to address the issue holistically - thinking in terms of the hydrology of a complete drainage basin, from the watershed to the point at which the river enters the sea would be a major step forward. DEFRA are ideally positioned to lead on this work but do they have the will or the capability?
- Local planning authorities should focus more on not simply covering the landscape with tarmac or concrete which do nothing more than produce immediate runoff - indeed they should be legally compelled to stop this happening. Additionally legally enforce a ban on any further development on floodplains - no development should be approved where flooding has ever taken place and add a further ten vertical feet
- Recognise the key role that ‘rewetting’ our uplands can play and invest in wider scale investigations. Along with this commence the reintroduction of natural vegetation and woodland to many of the upland areas thus turning them back to something that can retain rather than shed water - make this a key responsibility for Local Authorities. In the short term this will inevitably have an impact on the livestock currently using these hills but the benefits must outweigh the short-term costs for which farmers should be compensated
- Fundamentally change our approach to river management, moving the channels back to a more natural state, Stop clearing channels of all obstructions, stop straightening channels, allow sand banks, vegetation and meanders to develop all with the intention of slowing the water down. As an added benefit this would also be beneficial to our wildlife which as we know is currently struggling
Is any of this actually going to happen? To be honest in our current political system that is highly unlikely as a national policy - however if one catchment was brave enough to try this new approach and illustrate how well it could work it would then become difficult for our self-serving and next election focussed politicians to ignore it but do we really want to be seeing more of this?
**note - the images in this blog were all taken in Mid-Wales
By John Russell: A comprehensive 'big picture' summary with which I wholeheartedly agree.
By Peter Bayliss: Excellent exposition. I am impressed with your depth of knowledge on the topic and I was very pleased you referred to the Pumlumon project as anyone who follows the link will see that it has had a substantial and quantifiable result. Substance over form - as always. Peter
By Albert Pinto: Dear Mark, Your analysis is mostly spot on. Enhancing the water storage capacity of upland areas, especially those with vegetated soils, wetlands, peatlands is the order of the day. Certain urbanized parts of the UK are more than 50% impervious and this alone creates high overland flow and low baseflow, not too mention heat island effects and the accelerated erosion of streambanks. Moreover, the water cycle and the carbon cycle are heavily interlinked: wetter, biodiverse soils are able to store a lot more carbon too. And they can locally cool the climate through evapotranspiration so its a win-win against global warming. The example of Montgomeryshire is inspiring. Similar ideas of decentralized water management using small earthen bunds, weirs, small log dams, have been put into practice in Slovakia by Michal Kravcik, a hydrologist, who started the organization 'People and water'. Google "michal kravcik goldman prize" and "flow partnership kravcik people and water" for more information and pictures of his interventions.
By john evans: Nicely thought out and presented Mark, I hope the relevant people read and take note!
By Meurig Garbutt: Excellent article. Strange how so many people know so much about the basic science involved, yet the "experts" who advise our masters seem to repeat the same mistakes time and time again.Have they not learnt from The Mississipi region that building flood defences in the form of walls only leads to a raising of the river bed ( now above the level of the flood plain ). Upland drainage and increased grazing as centrally encouraged leads to increased run off rates etc etc. Mark, your article is well presented with a huge volume of supporting evidence,both scientific and anecdotal. Lets hope that one day soon those who make decisions decide to accept the advice of real experts and opt for a more long term flood defence strategy rather than a short term, visible,"look what we are building to protect you" approach, in the vain hope that it may work. Sadly I don't hold out much hope of anything like this occurring though.