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Flooding affected many regions within the UK, and was most severe in Yorkshire, Lincolnshire and the Midlands.
Prof Richard Hey, Prof of River Mechanics and Engineering, University of Birmingham, said:
“Some facts about rivers:
~ Natural rivers flood on average once every 8-9 months.
~ Their flood capacity is dependent on their flow and sediment transport regime ie dictated by natural processes.
~ Artificially increasing a river’s flood capacity, by widening, dredging or straightening the river can create long-term maintenance problems as the river attempts to naturalise itself and re-establish its original condition.
Combinations of dredging, bank stabilization, flood embankments are often required to maintain the unnatural state ie not sustainable.
Flooding issues
~ Flooding occurs where rainfall rates exceed the grounds capacity to infiltrate it, particularly in urban areas because of impermeable surfaces, but also when the ground is already saturated. These represent areas of flood production.
~ Flooding also occurs downstream from areas of flood production due to the flood wave migrating down river.
~ Flooding has been exacerbated by urbanisation, land drainage works to aid agricultural production and the ‘improvement’ of rivers to enable them to discharge flood waters downstream as rapidly as possible. Climate change will further increase the frequency of flood events.
Flood protection
~ Traditional flood alleviation schemes have treated the symptoms of flooding rather than the cause. Land use changes coupled with river training schemes is major cause of the problem.
~ To reduce flood risk it is essential that measures are undertaken to increase flood storage within river basins, to limit the amount of flood water generated in areas of flood production, and re-establish the natural form and function of natural rivers by recreating river meanders and reconnecting rivers with their flood plains. By storing flood water and reducing the discharge conveyance of rivers, flood levels in downstream urban areas can be significantly reduced.
~ Farmers, by taking their marginal valley bottom land out of agriculture, can be rewarded for providing flood protection for urban areas downstream.”
Dr. Andrew Wade, Aquatic Environments Research Centre. The University of Reading , said:
“Yesterday’s events are a stark reminder that flooding, which is a natural occurrence, can have devastating consequences especially in urban areas. Current uncertainty in the future projections of climate variability means that it is difficult to predict future flood occurrence. Further science to quantify the likely impacts of climate change on flooding is urgently needed. In the future, improved protection from floods may be achieved by enhanced flood defences along some sections of a river, but a more complete solution must also involve managed flooding and water storage upstream of major towns and cities.”
Dr Joe Smith Lecturer in Environment The Open University, said:
“Our economy, policies and lifestyles all developed when fossil fuels were cheap and the climate stable. Neither of these things are likely to be true in a warming world. But it’s not all bad news – many of the actions we need to take to respond to climate change could help us deal with some of our existing problems. Slashing traffic congestion, better health and quality of life in cities and eliminating our energy insecurity are just some of the benefits that will come from pursuing dramatic reductions in carbon emissions.
Whatever we do in the next couple of years cannot save us from the fact that our past emissions commit us to decades of climate change. However we should bear in mind that the kind of ‘weird weather’ we’ve seen in the last week is nothing compared with the consequences likely to be felt in vulnerable parts of the developing world.”
Dr Kevin Hiscock, Hydrologist, University of East Anglia, said:
“Climate change scenarios for the future indicate that rainfall intensity will increase: there will be fewer rain days but when it rains it will fall in larger volumes. There is, however, natural variability in the climate which leads to both droughts and floods. Seasonal weather patterns are expected to change under climate change with warmer, wetter winters but longer, drier summers. The current heavy rainfall may be part of the natural variability, although unusually extreme. The current situation in northern and central England exposes the possible threat of flooding under climate change and our ability to adapt. Storm water drainage systems in our older cities may not be able to cope with increased rainfall intensities and what we have witnessed in Sheffield recently and previously in Boscastle in 2004 and Carlisle in 2005 suggest that we need to improve our flood defences and drainage infrastructure. A consequence of heavier rainfall is a rising water table and this recently recognised phenomenon of ‘groundwater flooding’ can only exacerbate surface water flooding under extreme rainfall events.”
Professor Rod Smith (who is currently stranded in Sheffield due to the flood water), Professor of Mechanical Engineering, Imperial College London, said:
“There was a great flood in Sheffield (the “Great Sheffield Flood”) in 1864, on 11th March, where about 250 people were drowned due to bursting of a dam. The water flooded down the same route as it did yesterday. It was the biggest tragedy in Victorian engineering history. Something similar happened in Home Firth in 1852 where 81 people were drowned – a reservoir collapsed there as well.
“These events are becoming more frequent and as calculations for dam safety are based on statistics of the past, the allowance made for overflow may not be sufficient. The one thing you cannot allow with a reservoir is for the water to overtop the wall – once that happens it will begin to erode the wall as most reservoirs have earth embankments with a clay core.
“This event is by no means over; the run off from the hills will build up as the flow of saturated water increases. Following this, the bridges need to be carefully inspected for scour i.e. the erosion of the bridge foundations by the flood water.”
Dr Jean Venables OBE FREng, Chief Executive, Association of Drainage Authorities, said:
“I should like to first of all send sympathy to all those who have suffered loss.
•,”We must also be grateful to all in Internal Drainage Boards, the Environment Agency and the Emergency Services, and those who have worked such long hours over the last week to assist people.
•,”It is the wettest June on record and with such a slow moving storm it is both technically difficult and impossible to fund schemes which would prevent all flooding and the flow has exceeded the design capacity of the system in place. It is however imperative that we maintain the current flood defence infrastructure and ensure the capacity and conveyance of existing channels is available for flow.
•,”The amount of maintenance money allocated by Defra to the Environment Agency to maintain its flood defence assets is not sufficient. High, medium and low maintenance programmes has been adopted by the Environment Agency to prioritise allocation of these insufficient funds resulting in, in effect, no maintenance in low priority areas. It is impossible to predict where these intense storms will occur in the future and if it occurs in a low maintenance area flooding will occur that could have been avoided or minimised.”
Brian Wimpenny, IMechE Safety & Reliability Group, said:
“What we should perhaps be looking at here is if we can implement less expensive flood defence structures and if we can build cheaper ones that could be more easily repaired. The infrastructure of this earth dam for example, is going to be more difficult and extensive to repair than a dam which has been built at a higher level.”
A spokesperson from the Pennine Water Group, University of Sheffield, said:
“The Pennine Water Group knows only too well about the tragedy of flooding, having worked with many affected communities. Events such as these on our own doorstep remind us all of the urgent need for a new, seriously integrated approach to urban water management in these times of apparent climate change.
“Flooding can come from rivers, from an overloaded drainage system during heavy rainfall, or a combination of both. In urban areas it is essential that the drainage system is designed in an integrated and co-ordinated way and that it is adaptable to extreme climatic events, the severity and locality of which cannot be predicted with accuracy.
“Intelligent responses to flooding constitute a range of strategic responses that increase the resilience of communities to extreme events.
“The devastating immediate disruption and long-term effects of floods such as these illustrate the need to incorporate water management early in the spatial planning process. House building greatly affects the water cycle and for developments to even approach sustainability, potential extreme climatic events, whether drought or flood, or both must be taken into account.”
Dr Simon McCarthy, Research Fellow, Flood Hazard Research Centre, Middlesex University, said:
“From the media reports so far it appears the flooding has been caused by an extreme weather event with some parts of the country experiencing flooding for the first time.
“Our research shows that preparing for and reducing the consequences of flooding is important. For those affected and the organisations charged with looking after them the consequences can last longer than expected: 1. people can be out of their homes for at least 18 months which is a huge disruption of their everyday lives and pressure on authorities 2. the health of those affected can suffer for at least 24 months after the event 3. people are often underinsured or do not have insurance cover particularly where there is no history of flooding.
“The Foresight report illustrates how with climate change extreme events will become more likely and far more research and preparation is required to take account of such events. In this respect flood risk management still requires far greater funding – the story does not stop with the excellent work that has already been undertaken on river flooding. So far the events illustrate where future attention is
required:
1. the risk of flooding from sewers and drainage 2. work on forecasting and warning response to extreme events 3. preparation and promotion to residents and those responsible for utilities and emergency services of possible breach risk from physical defences
“In all these respects we are in agreement with the Environment Agency that more funding and attention should be given to the flood risk from extreme events to meet the future climatic challenges.”
Jo Parker, Director, Watershed Associations, said:
“1 Climate change is bringing more intense rainfall so that a larger amount of rainfall falls in a shorter space of time. This means that water courses have to take larger amounts of water, although only for a short period of time.
“2 Reservoir dams are designed to cope with a certain amount of rainfall, which is assessed on past rainfall records. This ensures that the risk of a dam not being able to withstand the water flows from an intense storm is appropriate to the damage which would be caused from a dam break.
“3 All dams which retain more than 25 million m3 water above the surrounding ground level come within the 1975 Reservoirs Act. This means they are inspected regularly by civil engineers with special qualifications controlled by DEFRA and ICE. A supervising engineer must inspect a dam at least annually and is responsible for initial assesmnet of any problems which may occur. An inspecting engineer will carry out a very detailed inspection of a reservoir and dam every 10 years.
“4 Risk assessments ahve to be carried out as part of the ongoing inspections. This may include review of rainfall records and flood calculations.
“5 The Reservoirs Act is enforced by the Environment Agency, who recently introduced an incident reporting system so that any problems with dams are reported so that all engineers involved in dam safety can learn from these incidents.
“6 In the case of Ulley, the supervising engineer will make an initial assessment. If required an inspecting engineer may called in to give additional advice. The sort of action which may be taken includes lowering the level within the rseervoir through opening additional drainage valaves or bringing mobile pumps to pump over the dam and providing additional shoring for the dam itself.
“7 This country has an extremely good record on dam and reservoir safety, largely due to the fact that reservoirs are subject to continuous surveillance with a pool of experts available in the case of any concerns.”
Professor Bob Spicer, The Open University, said:
“Basically the events we have seen over the past month and in particular the last 48 hours are typical of the kinds of things we can expect more of in the future. A warmer world leads to more evaporation but also more rainfall and the storm systems associated with a warmer atmosphere produce heavy downpours.
“Flooding is made worst by several factors:
– confining river channels by urban development instead of letting them naturally expand over the floodplain (if the retaining walls don’t fail this just moves the problem further downstream)
– concreting over naturally absorbent land surfaces so more water runs off into sewers and river courses.”
Prof Howard Wheater, Department of Civil and Environmental Engineering, Imperial College London, said:
“Summer rainfall in the UK tends to be of higher intensity and shorter duration than winter. For rural river catchments, the normal flood season is the winter, when long duration rainfall wets the catchment, and a greater proportion of rainfall appears as river flow. The recent floods are an unusual combination of intense rainfall following a sequence of events that have wetted up the catchments.
“Is this a symptom of climate change? Maybe. We expect climate change to lead to more intense rainfall, and there is evidence that short duration rainfalls have become more intense over the last 30 years. However, extreme events are expected to occur due to natural climate variability.”
Dr Dave Reay, School of Geosciences, University of Edinburgh, said:
“The numbers are stark: today there are an estimated 1.8 million homes in England and Wales at risk of flooding and climate change will put more and more homes at risk. If we fail to address climate change then, by the year 2075, flooding could be costing us an extra £1 billion a year.”
Terry Marsh, Centre for Ecology & Hydrology, said:
“More than a month’s rainfall in 24 hours is not an unusual occurrence during a British Summer. Such events have return periods of 4 to 8 years. However, what is unusual is the wide spatial extent of heavy rain across England over the past two weeks.”
“It has been a notable hydrological June with the combined May/June rainfall total likely to be one of the highest on record. Exceptional rainfall has produced flash flooding in many parts of the country (mostly in steep rural catchments) often followed by significant fluvial flooding as river basins become saturated.”
“In early May soil moisture levels were some of the lowest on record and another dry summer seemed on the cards. The recent heavy rain has extended the normal recharge season and allowed groundwater aquifers fill. It is therefore extremely unlikely we will see water shortages later this summer.”