December 31, 2015

expert reaction to flooding

Heavy and persistent rainfall has caused flooding in various parts of the UK, with northern England and southern Scotland particularly badly affected.

Prof. Jim Hall, Professor of Climate and Environmental Risks and Director of the Environmental Change Institute, University of Oxford, said:

“A country that is resilient to flood risk would look very different to the situation we are in now – land use in rural and urban areas, buildings and infrastructure would be radically changed. Reconfiguring floodplains, coastlines and cities to be more resilient to flooding is a long-term programme. This crisis is a wake-up call. We should start a national debate about the tolerable level of flood risk in a changing climate; and establish a long term vision for how to build a nation that is resilient to flooding.”

On a separate aspect:-

“Scientists have been debating for the last seven years the notion that “stationarity is dead” [1]. This means that the assumptions upon which our estimates of flood risk have been based for the last sixty years are no longer tenable, because of the effects of climate change. The sequence of record-breaking floods we are experiencing is beginning to teach us what the death of stationarity might look like – events that would previously have been considered extremely rare happening year after year.”

[1] Milly et al, Science, 2008

Dr David Stainforth, Associate Professorial Research Fellow, The Grantham Research Institute on Climate Change and the Environment, London School of Economics, said:

“The latest floods demonstrate some of the challenges in responding to climate change. The biggest is to separate what is known with confidence from what sits in the realm of research challenges. The former requires action across society. The latter requires communication to young up-and-coming scientists that the challenges in climate science are as big and as fascinating as those in fields such as astrophysics, particle physics etc.

That a warmer world is likely to lead to increased winter rainfall, particularly intense periods of rainfall, over the UK, comes from well understood science. Furthermore, recent research has shown how there has been a clear pattern of increased extreme rainfall events over parts of the UK – particularly Scotland. There is therefore a clear and robustly understood need to adapt our society to cope with such events. This understanding is not new. However, in responding to the need to adapt it is tempting to call for bigger and better computer simulations. Such calls should be treated with great caution. How to use such models to provide information in support of local flood management (such as the design of flood defences) is a source of intense scientific debate and disagreement. We need investment in new approaches to understanding how the details of future climate (e.g. local river flows) will change, and how to use computer simulations. There is a risk that the recent events in Northern England and Scotland will instead be used to justify more investment in models instead of in research on climate science. Computer models of climate are one tool for specialists but what we currently lack is not a better model but expertise on how to use them most appropriately. We already know enough to know that flood risks have increased and are only likely to increase further.”

Prof. Hannah Cloke, Professor of Hydrology, Department of Geography & Environmental Science and Department of Meteorology, University of Reading, said:

“Our national planning policy needs to very specifically ensure that development is not permitted in and around locations under flood risk. The only exception to this would be fully amphibious architecture which allows people to live with floods and makes space on the floodplain for floodwaters to be stored.

There are many issues that could be strengthened in our current planning policies including ensuring Sustainable Drainage Systems are fully and specifically supported early on in the planning stage and that local planning authorities are supported so that they can have the internal expertise and funding to challenge planning applications that do not consider flood risk adequately. Just focussing on Sustainable Drainage Systems is however not enough and we must consider the whole catchment; we need to understand what’s going in where and how water is moving through it and try to hold back the water where we can. This will help us be more resilient to both floods and droughts, and flooding from very heavy rainfall in the summer as well as winter storms.

We need to also ensure that we are building back better after floods by flood proofing our homes, raising them up where possible and supporting managed retreat over the longer term. We can adapt and be prepared for future flooding if we take action now. One of the most important things we can do is change our mindset to expect flooding and find ways of learning to live with it.”

Professor Andrew Watkinson, University of East Anglia, and author on Foresight Review on Flooding and contributor to Pitt Review, said:

“The Government has been given ample warning by the Foresight Review on Future Flooding (2004) and the Pitt Review (2007) that the risk of flooding in Britain would increase as the result of a whole range of drivers including more intense storms and land use management, both of which have undoubtedly played a part in the recent floods. Perhaps this is happening more quickly than we anticipated, but we know what to do. There is no single solution to the change in flood risk, but rather a portfolio of responses is required including strategic engineering works, changes in land and river management, modernising urban drainage systems and changes in land use planning. This requires a more integrated approach to flood risk management and an increase in funding.

Prof. Nigel Arnell, Professor of Climate System Science at the University of Reading, said:

“Many records have been broken in the last few weeks, and as climate changes we can expect more records to be broken in the future. When the water levels go down, we need to look again at the levels of protection actually provided by our defences and at how we incorporate our expanding knowledge and experience of a changing climate in both scheme design and update. And we need to prepare contingency plans for when defences are overtopped – as they will be with increasing frequency.”

Prof. Piers Forster, Professor of Climate Science, Leeds University

“There is no doubt in my mind that climate change is partly responsible for the flooding across the North of England. This December is around 5C warmer than normal and physics tells us that 24 hour extreme rainfall increases by 7% per degree. The high temperatures are the combined effect of El Niño on top of a man made global warming trend. These Floods are in part due to greenhouse gas emissions Q.E.D.”

Professor Myles Allan, University of Oxford, said:

“The armchair meteorologists who continue to insist this is all just weather are starting to sound a little bit like Aunty Mabel expressing surprise at her remarkable luck in boardgames. The weather has changed, and we have changed it: get used to it. Those with more open minds are asking ‘is this the new normal’? Unfortunately, the answer is ‘no’ — ‘normal weather’, unchanged over generations apart from random fluctuations, is a thing of the past. When families reconvene for Christmas in the 2040s, the envelope of ’normal weather’ will have shifted by as much again as it has already shifted since the 1970s. Which means we increasingly rely on computer-simulated weather for long-range planning: an important point for those who still can’t resist sniping at our long-suffering Met Office.

An increased risk of intense, short-duration rainfall events in mid-latitude regions has been predicted consistently for well over a decade as part of the pattern of human influence on precipitation. So far, we see a small but robust signal in individual events: around a 40% increase in the risk (see http://www.climatecentral.org/climate-change-heavy-rains-uk-storm-desmond). And if the risk of individual events has increased by 40%, then the risk of two separate events occurring in the same month has almost doubled.”

Dr Paul Williams – Royal Society University Research Fellow, Department of Meteorology, University of Reading, said:

“Simple physics tells us that warmer air can hold more water vapour. The global warming that we have experienced so far has increased the atmosphere’s moisture storage capacity by about seven per cent.  This is undisputed science and it clearly increases the potential for extreme rainfall and flooding.”

Prof. Roger Falconer, Professor of Water Management at Cardiff University and a Fellow of the Royal Academy of Engineering, says:

“I believe the time has now come when we have to look at major engineering solutions to address some of the unprecedented flooding challenges that we have seen in recent years. Although efforts to raise embankments are very commendable, the problem with raising embankments is that one solves the problem for one part of a river reach, but only to move the flooding problem further downstream.

“In my view the principle of holding the water back in the top of the river basin is the right approach – this being the principle behind planting more trees and vegetation in the upper catchments. However, trees, vegetation and woody dams only deal with relatively small floods. To withhold the large volumes of water being deposited under the current storms we need to consider more significant flood storage alternatives such as reservoirs in the upper catchment or natural bankside storage reservoirs.”

Professor Chris Rapley, UCL, said:

“The following extracts from the Met Office Report “Too hot, too cold, too wet, too dry: Drivers and Impacts of Seasonal Weather in there UK” published in March 2014, which is one example of many similar reports from numerous sources, demonstrates that expert advice on climate change risks has not been taken into account appropriately by Government Ministers. The previous Environment Minister, Owen Paterson, and the Treasury, who appear to hold similarly dismissive views on the reality and threats of climate change, stand accountable.

“It is difficult to detect trends in rainfall, because the number of storms and the amount of rain in individual storms both vary so much from year to year. Nevertheless, in the Northern hemisphere mid-latitudes (which encompass the UK), where the long-term observations are densest, there is a robust trend of increasing precipitation4. Attribution of precipitation trends suggest evidence of human influence at latitudes similar to that of the UK29.…..

The longest-running UK series of observed rainfall is the England and Wales precipitation record, which catalogues monthly rainfall accumulations since January 1766. The record shows very large year to year and decade to decade variations in rainfall (see below), which makes trends hard to detect. There are suggestions, however, that the character of daily UK precipitation has changed over the last 50 years. There is evidence that heavy rainfall events may have become more frequent over time31: What in the 1960s and 1970s might have been a 1 in 125 day event is now more likely a 1 in 85 day event”.

Chris Huntingford, Centre for Ecology and Hydrology, said: 

“Extreme rainfall events and related flooding have always occurred. The question is do we have adequate flood defenses for these natural fluctuations? Furthermore there are signs, for parts of Europe, that global warming is making rare events more frequent. A warmer world has a higher “atmospheric moisture holding capacity” which can intensify storms. There is also evidence that higher temperatures may be altering average storm track positions.”

“The starting point for understanding risk of high rainfall events is always a comprehensive analysis of previous records. But the problem with building the science of extreme events is that, by definition, they are rare. To create a full picture, beyond what only measurements can provide, we have to infill with computer simulations. Quite rightly there is skepticism about computer-based studies, but metrics do verify Meteorological Office weather forecasts are now remarkably accurate. By pulling together the maximum possible computer resource, and running these weather forecast models thousands of times – and for alternative carbon dioxide levels – a picture can be built of how often severe storms can be expected. This is by scanning in full across the naturally chaotic system of UK weather patterns.”

“As research starts to provide, with high confidence, the probabilities of events such as witnessed this month – and how these might be potentially changing – then this information can drive very high resolution hydrological models. Their projections, down to almost individual street-level, will aid future planning. The UK science community will rise to this challenge – indeed this has to happen. Never again should so many families have to suffer the heartbreak of seeing their homes and businesses so extensively flooded as through this December.”

Colin Thorne, Professor and Chair of Physical Geography, School of Geography, Nottingham University, said:

“It’s increasingly apparent that flooding is severe this winter (as it was in 2013/14) and that it is not over yet by a long chalk. Things may get considerably worse if the sequence of north Atlantic depressions continues.  I’m currently in the USA: Texas was hit by another massive storm the day before yesterday; today Missouri continues to experience torrential rain and widespread flooding is expected, including from the Mississippi River. The jet stream carries such storms across the Atlantic and towards the UK………..

Flooding this winter may prompt the government to launch a new review of flood risk management policy, practice and investment.  I expect that the findings will be similar to those of the government’s original Flood Foresight Project and, the Flood Foresight Update conducted alongside the Pitt Review in 2008.

In my opinion the studies the government initiated in 2002 have already established what needs to be done to reduce the misery and economic costs due to future flooding that is becoming more frequent and severe. I also believe that the competent authorities are doing the right things: they just aren’t doing them fast enough. On top of that, it seems that climate change is kicking-in quicker than Flood Foresight forecast it would back in 2004.

I don’t think we need another review: I think we need to accelerate implementation of responses to future flooding identified by the Flood Foresight Projects and envisaged in the comprehensive Catchment Flood Management Plans (CFMPs) that have already been worked out for every catchment in England and Wales. That does require investing more money in flood risk management, but the return on this type of investment is a good one – usually the benefit-cost ratio is about 6 to 1.

We must spend that money wisely though – there is no ‘silver bullet’ that can prevent flooding entirely. We need to defend our cities, reduce the exposure of key infrastructure (especially electricity switching stations, water treatment plants etc.) and use a great deal more ‘managed flooding’ of farmland on floodplains to take more of the pressure off urban flood defences.  That will require local and national cooperation from farmers – who deserve and should receive compensation for enhancing the capacity of their land to store flood water that would otherwise end up in somebody’s home or workplace. We must recognize that floodplains are the farmers’ work places”

But we need to act now – and that necessitates a step change in funding, coupled with implementation of catchment-wide flood management that uses all the flood management tools and measures available in joined-up approaches that treat the causes of flooding and the flood events themselves, while also helping communities to reduce the impacts of flooding when it does occur.”

Where I think we do need further research is on how to make our cities more resilient to flooding –  recognising that urban flooding cannot be prevented entirely. Our urban drainage infrastructure is mostly old and was never designed to cope with the quantities of rain that fall out of the skies these days. We need to rethink urban stormwater management in British cities and we need to do so urgently”