November 14, 2019

expert reaction to UK floods

Reaction to the flooding across the UK following extremely high levels of rain fall. 

Nick Reynard, Science Area Head for Hydro-climate Risks at the Centre for Ecology & Hydrology, said:

“There is now growing scientific evidence that climate change will result in increased flooding, because, in general terms, a warmer atmosphere can store more water. Our research has indicated that northern Britain is likely to be one of the most affected parts of Europe, in terms of increased magnitude of flood events, over the coming decades.

“The amount of rainfall, and precisely where it falls, the land surface and how saturated it is, and the existing flood management schemes are just some of the factors that make the precise nature of each flood hard to predict in detail. 

“Land management can play a role in helping to prevent or control flooding, such as the use of floodplains or retention ponds or selected small-scale measures to reduce runoff rates. However, man-made flood defences are still required along with these more ‘natural’ schemes, as a basket of flood management solutions is necessary to better manage flood risk. 

“Unfortunately, nothing can be done to prevent flooding everywhere at all times.”

Prof David Sear, Professor in Physical Geography, University of Southampton, said:

“It never ceases to astound me when we hear all the same reactions to large flooding as we did during recent flooding episodes – notable in 2000, 2007, 2013, 2014 and 2015.  The points in common with all of these floods are clear: first and foremost they are dreadful events for those that are flooded. The impacts are not just for the headline today, but can impact on the long term mental health and wellbeing of the individuals affected, and the communities more broadly. Thus the focus now should be on the people and communities affected; with resources targeted at helping them cope and recover. Such events are a time to pull together and are often characterised by acts of incredible service involving neighbours, friends and families, local communities, faith groups and official bodies going the extra mile to provide shelter, food, clothing and other methods of mitigating the flood impacts.  These elements of the flood “story” are often underrepresented by media reports, which tend to focus on who to blame and what went wrong. As a veteran of many flood broadcasts, going back to the Chichester flooding of 1994, when – on a soggy evening when neither I nor the reporter was too pleased to standing outside-  I failed to provide the answer they were looking for – i.e. that someone or some organisation was to blame. Instead I simply stated the facts that the Chichester floods were primarily down to very high groundwater levels as a result of a sustained period of heavy rainfall. Needless to say the article did not appear on the news that evening. Subsequently I have witnessed further disappointment in the eyes of reporters when I have had to state the obvious truth – what causes very large floods (with the exception of dam breaks) is exceptional quantities of rainfall or, in the case of 2013, high seas due to a sequence of storms. In other words, the primary cause of flooding is weather.

“What causes flooding of properties and people is also usually quite obvious – flood risk is caused by people building, farming or sadly moving into places that flood. Sometimes, this is exacerbated by poor land and channel management, and very occasionally by mistakes in advice or operational actions, but these are not the primary cause of the flood risk. Large scale flooding of the kind witnessed this last week, or in Cumbria in 2009 and 2015 is seldom down to dredging (much sediment is mobilised during these big floods and results in changes in channel capacity until like musical chairs, the flows stop and the sediment drops out), or any one group of people. Rather, it is down to a legacy of decision making and actions stretching in some cases back over centuries, that resulted in modifications to river channels and floodplains, land cover and drainage in the surrounding catchment. Blame under these circumstances is misguided and unhelpful, and politicians and reporters should be very careful to ensure they understand the facts of flooding before seeking to champion any particular action (or cause!).

“What normally follows in the wake of a flood is a major call for some kind of specific action – dredging in the Somerset Levels in 2014 (I wonder what the status of that is now? I’ve heard the sediment has returned – as it must because of upstream farming releasing soils as the landscape goes through its agricultural cycle), increased flood protection in Keswick in 2009 – the latter famously overtopped in 2015. Following the 2015 Desmond and Frank floods, people finally recognised that something other than expensive and time-limited flood defences were needed – notably smaller scale and numerous local actions across the catchment that can “slow the flow”. Examples have been championed (e.g. Pickering Beck). This has now become a campaign of itself, but the scientific community early on, urged caution – catchment based solutions, Natural Flood Management (NFM) can indeed protect local communities from some flood risk, but the evidence for its effectiveness decreases as the size of the flood and the size of the river catchment increases. Moreover, it is not without impact – most NFM relies on temporarily flooding someone else’s land.

“So what to do? First fix those who are flooded. That has to be the primary goal now and into the future including help to cope not just financially but also to recognise the longer term impacts. Second, conduct a clear and transparent review of evidence to build a picture of why the flood impacts happened – (we know the flooding was caused by lots of rain). Thirdly, work collectively to identify what could be done better and by who – looking carefully at all possibilities including changing who has responsibility for what during the flood event. Right now the process of flood risk management is complex, and delivery of post-flood measures is not down to one authority – an output of earlier flood reviews.  Throughout the process, we need to build consensus based on evidence – get the NFU, EA, City Planners and local communities to work together to develop catchment-based flood management plans that really seek to address the risks and allocate clear responsibilities in delivering these. Be ambitious but also creative – if flooding upstream fields for a short while would really help – then work with the farming community to pay them for delivering the benefits. If needs be, charge a levy on those who benefit, or use the savings on flood defences to help support community schemes. If dredging and embanking can be really shown to provide the only realistic protection into the future, then cost it properly and consider alternatives – but if it’s the only way and the costs can be met, do it, but do it so as to leave the river environment better than before, and the communities safer then before. Finally, stick to the evidence and avoid the temptation to react to the loudest voices and most successful campaigners. Pointing fingers now, without any hard evidence is almost irresponsible.

“Idealistic? – perhaps, but it’s not like we have not been here before or indeed going to be here again!”

Dr Jess Neumann, Hydrologist at the University of Reading, said:

“It’s completely understandable that local communities want to know what has caused the floods and whether steps could have been taken to help reduce the impacts. However, we do not have the evidence that dredging rivers is a long term or cost effective solution. Dredging would need to be carried out on a regular basis, and at a time when resources are already very stretched it would be an impossible task to say that certain areas should be prioritised over others. We also have to consider the knock-on effects; dredging moves water faster through an area, potentially moving flooding issues downstream rather than alleviating them, while there can be also detrimental impacts on biodiversity, bank erosion and water quality. We need to be looking at other nature-based solutions that are suited to the catchment environment and which offer more long term benefits.”

Prof Hannah Cloke, Professor of Hydrology, University of Reading, said:

“Our climate has changed and this is just the start.  We need to not just be great at responding to each flood, but instead adapt to this norm, and that is exactly what the Environment Agency were calling for when they put out a new strategy in May.

“The Environment Agency are doing a good job in difficult circumstances without enough resources.  This is a complex problem.

“We can’t solve this with flood defences alone and dredging can only ever be a small part of the answer.

“We have to think of the whole shopping bag of flood risk management strategies including natural flood management, better planning and knowing what to do when a flood is forecast.

“No government agency can protect everyone from flooding – that is completely infeasible.  It is about managing the risk. 

“It’s the rain not the Environment Agency that causes flooding.

“With any wet period like this one it is inevitable that some people will be flooded. The important thing is to know how to prepare for that flooding.”

Dr Dann Mitchell, Associate Professor in Atmospheric Science, University of Bristol, Cabot Institute of Environmental Change, said:

 “A well understood consequence of a warming planet is that the atmosphere can hold more moisture – meaning more water is available to ‘rain out’. More rain means higher chances of flooding, and the flooding in Yorkshire and the Midlands is a clear vision of that theory playing out, with around a months worth of rain falling in the space of a day. Other factors are crucial for these particular floods, including the decision not to build significant flood-defences in the regions. 

“Our latest science shows that extremely wet days during UK winters are currently up by around 15% compared with previous decades, at least in the north of England. Wetter future winters is a consistent projection in our best UK-focused climate models, with some predicting a 30-35% increase in rain by 2070. There is no getting around the fact that our government and town planners need to invest significantly in UK flood defences to alleviate the very likely scenario of future extreme flooding.

Professor Roger Falconer FREng FLSW, Emeritus Professor of Water Engineering at Cardiff University and a Fellow of the Royal Academy of Engineering, says:

“The challenge of flooding often arises in steep catchments where the water drains rapidly off the steep upper reaches and then flows much slower on the flatter land further downstream, as is the case for much of Yorkshire. In my view the most viable solution for the future in many parts of the UK is to build flood control dams, often referred to as flow-through or perforated dams, which are specifically (and only) built for flood mitigation (see: https://www.ctc-n.org/technologies/flow-through-dam-flood-control). Such a dam fills during flooding in the upper parts of the river basin and is then emptied, under controlled conditions, after the flood. The principle is not that different from Natural Flood Management, where one builds woody dams and plants trees etc. in the upper reaches of catchments to hold back the water. However, for some of the recent floods we have experienced, woody dams and trees are insufficient alone to address the challenges of significant rainfall events; it is rather like putting a small sticking plaster on a major open wound to control profuse bleeding, i.e. they are ineffective alone for such conditions. With relatively large dams (much larger than woody debris dams), much larger volumes of water can be held back in the upper river basin. Furthermore, if the dam is only 10 metres high and impounds just one hectare of land then this would be equivalent to paying farmers to allow 20 hectares of land to flood to 0.5 metres. Compensating farmers for flooding their land is not always a viable solution to reduce flood risk as they need to be able to plant crops on flat land at certain times of the year etc. Dams like those outlined above are quite common in the US (see dams in: https://en.wikipedia.org/wiki/Flood_control).”

Declared interests

Nick Reynard: Nick’s research has been funded by a range of organisations including NERC and the EA

Prof David Sear: David receives funding from NERC, Defra, Natural England, Environment Agency. He is affiliated with the University of Southampton and the River Restoration Centre.

None others received.