Select Committee on Environment, Food and Rural Affairs Minutes of Evidence


Examination of Witnesses (Questions 580 - 599)

WEDNESDAY 12 DECEMBER 2007

DR ANN CALVER, MR TERRY MARSH, PROFESSOR JOHN MITCHELL, MR STEVE NOYES, DR CHRIS WEST AND MS JACQUI YEATES

  Q580  Paddy Tipping: Coming to your work, Dr Calver and Mr Marsh, in your evidence you suggest that fluvial flooding is going to get less because there is going to be less snow around and the soil is going to be drier. We have had a prolonged discussion today about urban flash flooding. As policy makers, do you think we ought to be investing in the urban environment and taking measures in the urban environment rather than flood defences?

  Mr Marsh: There is an issue there on the point we made in our notes to the committee. In terms of fluvial flood risk, we did not say that it would reduce. We said that there were factors that would moderate flood risk in the future. In terms of fluvial flooding, there are two elements and a separate feature which I will come to. The 1947 flood, the largest of the last century, was primarily the result of snow melt. There was some rainfall but it was a major snow melt event. The largest event in the 19th century was probably the 1809 flood, and that was in fact rainfall running off frozen ground, with some snow. These are frozen ground and snow melt events. In a warming world, climate change is seen as the villain of the piece too often, but, in a warming world, that type of exacerbating factor will be less important. The other issue is in relation to the dry warm summers that we are likely to get. Under those circumstances, the soils will be drier for a longer period. One would envisage the reason that we have so few summer floods is that dry summer soils are able to absorb a substantial proportion of the rainfall. In the future, it may well be that the flood season, if you will, is contracted. Those two elements could come together to reduce flood risk. There is one final point in relation to fluvial flooding, because there is a good deal of public fear out there that flooding is going to increase very rapidly. The Thames is an interesting example. It has one of the longest records in the country for flooding. There is no trend in the flood magnitude on the Thames, and that is over a period of 130 years. You could go further and say that flood risk has actually declined, not vulnerability to flooding because of development on the flood plain—there is no change in flood magnitude through time—but the capacity of the channel of the Thames has increased. The Thames is a more efficient river, less romantic but more efficient, than it was 100 years ago. The weirs have improved. There are flood relief schemes. Dredging has created a more efficient channel. An amount of flow, an amount of water, that would have produced a flood in the 1930s and 1940s is now readily accommodated in the lower Thames. These issues are important. Some relate to potential climate change and some relate to river management. If you also look at the Warwickshire Avon where there was a staggering magnitude of flows, there is no compelling long-term trend in flood magnitude there either. Things may change but you have this relative stability through a period when temperatures have increased, not as much as they are likely to increase in the future, and the rainfall patterns have changed from a situation where in the 19th century summers were quite often wetter than winters and now we have wetter winters. You do have this stability through periods of climatic variability. I am not saying that these are grounds for being sanguine at all. It may change but you can see that it is relevant to the discussion, particularly in relation to the public's perception of how bad things could be and how quickly. I am not sure I am best placed to answer the question about—

  Q581  Paddy Tipping: Stick with that for a minute. There are reasons to be cheerful?

  Mr Marsh: There are reasons to be cheerful in the sense that there is some resilience to flood risk, which perhaps is not discussed. If we get wetter winters and more intense storms, then that resilience will be tested but there is a degree of resilience.

  Dr Calver: There is just a quick point on whether we should invest in urban areas. In Environment Agency and Defra parlance, risk is probability times consequences, and consequences are usually likely to be more compelling in urban areas. The point I would really like to make is that urban drainage systems were designed perhaps more for drainage than for conveying floods, and they are to a very low standard in terms of recurrence interval events. I think new developments are somewhere around the 30 years but many, many are a lot less than that. What we badly need, if we are going to invest in that type of approach, is knowledge of urban drainage behaviour above the current rather low design levels. When we know how they behave, we can then see if it is worth investment there. What developers must do is not only solve their development patch but not pass the problem on within an urban area and not pass it on within a catchment either.

  Mr Noyes: This is a really important point. One way that I tend to think about it is that a lot of effort and investment has gone into understanding the meteorology that gives rise to rainfall and the effect that then has on river catchments and then what you do about managing the effect of rivers in flood through managing the flow of the water but also on the flood defences. I think historically that has been what one might call a tractable problem in the sense that the science and the engineering is established well enough to be able to do something about it, to understand what is going to happen in the atmosphere and what happens in the river catchment, and then how you deal with it, how you design the management and mitigation systems to deal with that. It is really only relatively recently that the problem that you described in terms of urban flooding, flash flooding, is beginning to become tractable because on an atmospheric scale we are now beginning to model the atmosphere at a resolution which is approaching the sort of resolution you would need to be able to do something useful. Ordnance Survey and the like are now gathering data around what is actually happening on the ground at that resolution and also importantly keeping it up to date. The water authorities and the Environment Agency are together beginning to keep more records of what they are doing. Probably for the first time it is becoming a tractable problem so that we can actually start to provide some useful advice around it. The area where it probably is possible in the longer term, and we have already talked about this but it needs significantly more work, is what is going to happen under climate change. On the one hand, in real terms, in terms of providing forecasts so that emergency services can respond to something that is going to happen next week in an urban area, I think we are close, with more investment, to people working better together and being more focused on that issue to start dealing with that in terms of the here and now. With more investment in understanding climate change and the links to the hydrological impacts, then the engineering design solutions should be available for the future.

  Q582  Paddy Tipping: This is the work that you were talking to us about earlier, Jacqui?

  Ms Yeates: I understand the problem is that as much as they can model the future climate change, ideally I believe they would like 30 second information in terms of future climate change. As the climate modelling people will tell you, you just cannot have that. So there is still a mismatch between the type of information required, because obviously rainfall intensity is very important and that is why they ideally would like 30 second rainfall. They cannot have it and I believe they ended up using two minute rainfall with very large cautions around it given to them via a weather generator. There is still a problem with the level of information needed for this type of work and what can actually be provided with any type of accuracy or certainty in it. It is still very uncertain information we are dealing with.

  Q583  Paddy Tipping: This would be interesting data for insurance companies?

  Ms Yeates: Yes.

  Professor Mitchell: Just to comment on the extreme events, in winter with both the mean rainfall and the extreme events, the tendency increases in virtually all models over the UK. As was indicated, in summer the mean rainfall is split between getting wetter and drier, certainly in England in the southern part of the UK. When one looks at the extreme rainfall, there is still a tendency, even in some cases where a model is producing a drier mean rainfall, for it to produce heavier extreme rainfalls and so the heaviest day rainfall increases—not in all cases but in many more than in the case of mean rainfall. As Steve explained, that is simply because you have a moister atmosphere and typically that is about 6-7% per degree. So you have a rule of thumb for that particular mechanism. There may be other things happening which might intensify the storm but, in terms of the temperature effect, there is a very rough rule of thumb of about 6-7% per degree in the maximum amount of water that the atmosphere can hold at a particular temperature.

  Q584  Paddy Tipping: Sticking with the reasons to be cheerful, you seem to be telling us that climate change can be more intense with heavy rain in summer but longer, more protracted rain in the winter.

  Professor Mitchell: Certainly it can be wetter with an increase in mean rainfall and an intensity in rainfall. In summary, the jury is split on what is happening in terms of mean rainfall but there is a tendency in some of the cases where models are producing a reduction in rainfall still to have an increase in the extreme rainfall.

  Q585  Paddy Tipping: On the climate change pattern, what about tidal surges? East Anglia was going to be overwhelmed at the beginning of November and narrowly escaped that. What is the pattern of weather change on some of those events like that?

  Professor Mitchell: In terms of storm surges, there are at least three main factors. One is what is happening to the land surface in the south-east of England as it is sinking. If you go to Scandinavia, it is rising. The second is the change in mean sea level. The third is any change in meteorology which increases the tidal events. If you look at the last UKCIP report, I think there is a case of a high emission scenario in somewhere like Immingham. A one in 100 year event became a one in seven year event. The majority of that was due to changes in the meteorology in terms of storm surges with slightly less than half the contribution coming from sinking land and changes in mean sea level. The more recent predictions that we have show a smaller contribution from storm surges and a similar contribution from mean sea level and so on. The predictions of storm surges are even less certain than rainfall. I think one should be aware of that, but that gives you a typical idea of changes in surges down the southern North Sea.

  Ms Yeates: That was the median high scenario and not the high emission scenario. If memory serves me correctly, it is medium high and not high.

  Q586  Chairman: Are all coastal areas potentially around the United Kingdom subject to storm surge? Could any one occur at any time?

  Mr Noyes: Yes, but to varying degrees. I think that is the point. Storm surges are common but when they become particularly severe is less common and it is largely the area around the North Sea coastline that is most at risk because of the collection of water in the sea pushing up. One way of thinking about it is that if you push a tablecloth on the table, it ruffles up. It is the same effect in that the wind pushes the sea; it gathers at the bottom of the southern end of the North Sea. You get storm surges all round the coast, during the winter months in particular, but what is particularly of concern is the shape of the North Sea basin and the gathering of water in the North Sea.

  Q587  Dan Rogerson: On urban flooding, and we are talking about modelling, just in terms of the weather that is on the way and the interaction you see when you are looking at the fluvial events, you have that relationship with the Environment Agency, which is very clear., When you are dealing with local authorities, I imagine that is quite a different relationship to have one organisation with lots of others. How does that interaction occur?

  Mr Noyes: We deal with a lot of different agencies. For example, if there is going to be an exceptional weather event this coming weekend, we would already be talking, as you say, to the Environment Agency. We talk to the local authorities, both directly in terms of the ones that are most likely to be affected, and also, through the Civil Contingencies Secretariat, to the Cabinet Office. We also have contacts with the Fire Service and Police directly. At different stages of the event, then we would be talking to different people. If, for example a Gold, Silver or Bronze Command was established, we would be in regular contact with them. Indeed, we have a small team of people who are located around the country called our Public Weather Service Advisers whose sole role is to communicate with that community. To the extent that they would be talking to them at any time of day or night, they may indeed deploy to work alongside colleagues in a Gold Command, should they wish it. We talk also to the Cabinet Office and to government departments directly and to the community of utilities of course which have an important role to play, whether it be the water utilities, energy utilities, Highways Agency or Network Rail and so forth. Those dialogues are happening all the time. We tailor our messages to the people to whom we are talking. As you say, the Environment Agency would probably want to have a dialogue with us in one particular context, whereas Network Rail as one example would be talking about the issue in a different context.

  Q588  Dan Rogerson: Is that on the basis that they are asking you questions and you are providing the answer or is that on the basis that you think there is a matter of concern and you are initiating the process?

  Mr Noyes: We initiate that. There is a protocol whereby we contact them. There is a routine service that happens in terms of alerting people during the routine service that operates 24 hours a day, seven days a week. In addition to that, over recent years we have developed matters and we have found at the operational level that sometimes when we are talking to our customers the high impact exceptional events do not become escalated up. To get round that, at senior level we will make direct contact with senior management in those customer organisations so that senior management is aware that something is going to happen and then they can gear up their own organisations.

  Q589  Dan Rogerson: But is it because of the way flood defences have been focused on the river catchments? Is going into the Gold Command process and all the rest of it really triggered by river catchment stuff and the urban stuff is tacked on to it or if you are likely to have an event that is happening in an area that is not part of the significant catchment? Do you see what I am trying to say? How would that go direct to a local authority rather than through a wider process because of a concern over river catchment?

  Mr Noyes: There is a routine protocol for the warnings that we issue, and indeed the warnings that the Environment Agency issues. We have something called the National Severe Weather Warning Service, which would go to all the local authority responders, but we do not deal with flooding; we deal with heavy rain. The Environment Agency then deals with warnings related to rivers. There is a gap, which is indicated in our submission in terms of where you are driving to and that is the pluvial or flash flooding, in UK capability in terms of warning people about that risk.

  Dan Rogerson: As the MP for Gloucester and as you have mentioned a couple of times, the much smaller event we had this year was far more connected with the surface water coming there. I guess because the community had been through it so recently, they were far more pragmatic about it and were able to analyse for themselves what had happened and so it was very different.

  Q590  Mr Williams: On the tidal surge issue, I can understand how seasonal and tidal events are exacerbated and how wind can exacerbate that, but what I did not understand was how in very low pressure conditions the actual level of the sea rises. Is that right?

  Professor Mitchell: That is true.

  Q591  Mr Williams: What causes that? Is the water becoming less dense or is it moving?

  Mr Noyes: Think about the weight of the atmosphere pushing down on the oceans. Pressure is just a way of measuring the weight of the atmosphere above you. As the pressure reduces, then the sea can rise higher, and so, yes, it is effectively expanding.

  Q592  Mr Williams: So it is becoming less dense?

  Mr Noyes: Yes. It is rising up higher.

  Dr West: It is rising up higher. It is being pushed down more strongly elsewhere.

  Dr Calver: If I may add a point on that surge, the low pressure systems that cause this effect can of course also be associated with inland flooding. Occasionally you have what we call a joint probability situation with both inland and coastal flooding and that of course can be one of the occasions when you get very extensive flooding. It is worth thinking about spatial extensive flooding in general because that is when the emergency services are really tested. It is very bad if it happens in an individual place but if you get a spatially extensive event that is perhaps even worse. It is probably worth looking into some of the circumstances that promote those events.

  Q593  Mr Williams: Could you explain how that works?

  Dr Calver: Yes. The low pressure that Steve and John have explained and how that causes a surge is often also associated with a depression of a weather system. If that tracks over the country in a certain way, it can sometimes produce enough rainfall in locations so that there is big river flooding, coastal flooding.

  Q594  Mr Williams: That is not to do with the lifting of the water?

  Dr Calver: No, it is the precipitation associated with low pressure systems.

  Mr Noyes: There is a direct impact on rivers from the surge. If you go back to the East Anglia event we have talked about, and you can imagine the water egressing the land through the river, if you have a storm surge, it is like the tide staying in all day and so the water cannot leave the rivers. If you take the East Anglia event, the flood defences on the coastline held up, thank goodness, with just one breach but the flooding we did have, particularly in Norwich, was because the river flowing through Norwich could not get into the sea. There are circumstances which are fairly common where a surge will stop the river getting rid of its water.

  Q595  Lynne Jones: You commented a few moments ago that pluvial flooding, which is a new word to me, nobody is responsible for forecasting. Also, the Met Office in its evidence referred to the different system they have from most of Europe where there is one single agency responsible for all these forecasts. Are you implying that there should be changes and, if so, what and who should be responsible for pluvial forecasting|?

  Mr Noyes: There are two parts to the question and two answers. One is around pluvial forecasting and what shall we do about that, and then there is a second point which is: is there benefit to be gained from integrating more closely how we model hydrology and how we model the atmosphere. With regard to pluvial forecasting, because of capabilities that are coming, and we could potentially accelerate those capabilities, and, as I mentioned earlier, because of better understanding of what is going on on the ground in terms of Ordnance Survey, better records being kept of what is being put in the ground by builders and developers and water authorities and better modelling of the atmosphere by us, we can start really for the first time to be doing pluvial forecasting and warning in a sensible context. I think in Europe there is no difference. Everyone has the same problem. Everyone is trying to come up with a way of forecasting and warning early enough of flash floods so that people can do something about it. In the Boscastle sense, people could be contacted a few hours in advance and be told to evacuate to high ground so that they did not have to be lifted by helicopter, for example. That problem is the same in the UK as it would be in other parts of the world. Everybody is now getting to the stage where we think we can do something about that. The other is with regard to whether there is benefit to be gained from more closely coupling the responsibilities for hydrology and weather. We think that there is, and that is evidenced by what happens in Sweden and in France in particular within Europe. Why do we think there is benefit to be gained? For a start, if you take the example within the Met Office of the Hadley Centre, which looks at climate change and the weather forecasting business, which is our traditional, core business, by having them in the same organisation we have been able to develop our science and our modelling in such a way that we end up with a better understanding of climate change and the weather impacts that then helps our colleagues in UKCIP to produce better predictions of what the impacts will be. In the same sense, if you can couple modelling of the water that then has fallen on the ground with the way that you model the atmosphere and if the research and development that goes into those are done with the same aim in mind, then when we are developing our science for the atmosphere, we can be very much gearing that to what is going to be done in parallel with modelling the hydrology. At the moment, I think it is fair to say that there is not so much co-operation and coupling as there should be. There is a lot to be gained from putting much more effort into a unified approach to how we do that in the future.

  Q596  Lynne Jones: In practical terms, what are you saying? It has been proposed that the Environment Agency should take over this role. Are you disagreeing with that or are you saying that you just need a much better relationship or that you can provide better information to the Environment Agency? You also said a few moments ago that we could accelerate these capabilities. I assume things are going ahead with your new super computer which will enable you to increase the resolution of your predictions. What about other areas of research into hydrology? Have we got the resources in there that will maximise our capability in this area?

  Mr Noyes: Again, there are two parts to that in terms of the response. One is around who is best placed to provide that once we have the capability in place to do pluvial forecasting well. I will pass to John and colleagues to my right in terms of how we might do that and where the research should be focused. Bearing in mind that pluvial flooding is related to high intensity events and the response is quite quick, river flooding tends to be slower; there is more of a lag until the response. Pluvial flooding is very quick and therefore we need to get messages to the citizens very quickly, in the middle of the night potentially. You need an organisation that is used to providing that immediate advice to the emergency services. The Met Office's view is that we are best placed to provide that advice in an operational context because that is what we do now and we already have the contacts. We are there all day and all night every day of the year; the Environment Agency is not. That would be our view in terms of the actual advice to the emergency services and the public. With regard to the operational running of the models, it would make sense for those to be done together so that they are closely coupled. Where the research and development should be done is less clear. I will pass on to John for that.

  Professor Mitchell: To add to what Steve has said, in particular on the operational modelling, the running of the operational model I think would have to be done in the Met Office because in coupling an atmospheric model to a flow model, particularly if you go to high resolution perhaps in samples, there is a lot of data streaming out of the computer that has to be fed directly into the flow models. I think that is where we would want to see it. In terms of giving the warnings, I think that is just a matter of collaboration between the particular environment agencies and ourselves. In terms of the research, we do not have much expertise in-house in terms of flow modelling. We have looked to people like the EA and to CEH and in fact on the climate side we already have people working in Wallingford.

  Dr Calver: We do have a small Joint Centre for Hydro-Meteorological Research in the non-operational sense that links the Met Office with our hydrological researchers, which is quite a good model.

  Professor Mitchell: That research feeds both into the operational forecast and the climate forecast. There is the basis of that collaboration already. The third thing off the top of my head that is important is to second people particularly from the Met Office to the Environment Agency and vice versa to increase the knowledge and understanding of how the different systems work. It is significant that during the recent floods when we did mutually embed people my understanding is that it led to a much better understanding of how the different organisations work and enabled a much better service.

  Q597  Lynne Jones: I would like to explore the research issue and capabilities a bit further. Are you actually bidding to take over responsibility from the Environment Agency?

  Mr Noyes: We have indicated what our capability is and we think we are well placed to play an important role, and we have made our submissions to the Pitt Review that is underway at the moment. What Government decides to do we will wait and see. We have indicated that we believe we have a very important role to play and that our existing capability could be better exploited than it is currently. In that sense, I guess we are bidding but we are not saying that the Met Office must do this . We are saying there is a lot of capability in the Met Office that could be better exploited.

  Q598  Lynne Jones: We have to maximise our capability, obviously. I am referring back to Dr West's comments earlier about defining vulnerability and thresholds. He implied there was a lot of work that needed to be done to get to that level. Could I ask the other witnesses if they would like to comment on whether we are investing in that capability and have we got the right set-ups to achieve what you say we need to do?

  Dr Calver: Can I clarify whether you are talking about operational work or longer term research, please?

  Q599  Lynne Jones: I think both, in actually predicting and we have a lot of research being carried out by the Met Office in improving their predictive capabilities. I am mystified at some of the stuff that you have told us about this afternoon. I do not want even to try to understand it, but I want to know that you are doing the work and that everything that you think that we need is being done to respond as quickly as possible to predict and to be geared up, both in terms of the urban level as well and not just river and coastal flooding. Are we investing in the capability that we need?

  Dr Calver: I am only talking from the more strategic research view and not the operational view because I think that is beyond my remit. The important thing for hydrological research is that any flood research is also done in the context of other things that catchments are used for—water resources, the requirements of the Water Framework Directive, et cetera. Hydrology research, although it relates very much to floods, also relates to other things. If you ask researchers whether they need more money, there is always the great danger that they will say "yes". Flood research is done in our organisation. The Defra and the Environment Agency joint programme is a big client and a big funder and I would say that was well developed but could do with more funding. We are also funded by a Science Vote through the Natural Environment Research Council and CEH has a programme on water extremes, which includes flooding. I do not really think I can comment on levels of Research Council funding, except that we are always pleased if we get an increase at Spending Review time.


 
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