EPQ

Flooding in the British Isles: An Evaluation of Approaches to Flood

Protection and MitigationHenry Dawson

AQA extended project qualification

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Contents1 Introduction........................................................................................................................................3

2 Types of flooding................................................................................................................................3

2.1 Coastal flooding...........................................................................................................................3

2.1.1 Storm surges.........................................................................................................................3

2.1.2 Tsunamis...............................................................................................................................4

2.2 Inland flooding.............................................................................................................................5

2.2.1 Pluvial flooding.....................................................................................................................5

2.2.2 River (Fluvial) flooding..........................................................................................................5

2.2.3 Groundwater flooding..........................................................................................................6

3 Recent Flood Events in the UK............................................................................................................6

3.1 2007 Summer Floods...................................................................................................................6

3.2 2013/14 Winter Floods................................................................................................................7

3.2.1 Causes...................................................................................................................................7

3.2.2 Economic Impacts.................................................................................................................8

3.2.3 Social impacts.......................................................................................................................9

3.2.4 Political impacts....................................................................................................................9

4 Future...............................................................................................................................................11

4.1 Why flood impacts will increase................................................................................................11

4.1.1Climate changes...................................................................................................................12

4.1.2 Urbanisation and population growth..................................................................................13

4.2 What can we do to defend ourselves?......................................................................................13

4.2.1 Engineering flood control...................................................................................................14

4.2.2 Dredging.............................................................................................................................15

4.2.3 Natural Flood Management Techniques.............................................................................16

4.2.4 Planning policy....................................................................................................................17

4.3 Evaluation of approaches to Flood Management......................................................................17

5 Recommendations............................................................................................................................18

5.1 General Recommendations.......................................................................................................18

5.2 Approaches to Flood Prevention in Study Areas........................................................................19

5.2.1 Somerset.............................................................................................................................19

5.2.2 Thames Basin......................................................................................................................20

Summary of References Used..............................................................................................................21

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1 IntroductionFlooding has been a problem for residents of the British Isles since the Roman era1 and continues to be a problem into the 21st century, with 5 million properties and significant portions of the nation’s infrastructure under threat2. 20th century technological advances in mapping and flood defences have meant warning and mitigation has improved rapidly, leading to a reduction in deaths and greater information on flooding patterns. However, the frequency and magnitude of flooding is increasing due to global temperature changes3 and combined with increasing levels of economic property at risk of damage, this has led to concerns whether we must do more to protect ourselves against this devastating hazard4.

A flood occurs when water overflows or inundates land that's normally dry5. It threatens almost all of the global human population, with anywhere which rain falls under threat. However this is not the only cause of flooding, with short term threats such as breached dams or rapid ice melting causing inland flooding of floodplains. Coastal flooding is also a major issue, especially in the British Isles- due to the island geography. This occurs when high tides and/or storms breach coastal defences, inundating low lying and the heavily populated coastline with water.

Through this project I hope to describe the types of flooding and ascertain their varying potential to cause damage or loss of life within the British Isles. With the ever growing concern of the effects anthropogenic global warming will have, I will try and pinpoint some of the possible future impacts including the economic effects and political consequences. I will examine various approaches to flood prevention and mitigation and seek to make policy recommendations. My main areas of focus will be on the flooding on the Somerset levels and in the Thames Valley during the winter of 2013/14, but this paper will also reference flood impacts elsewhere in the UK.

2 Types of flooding6

2.1 Coastal floodingCoastal flooding occurs in two main ways:

2.1.1 Storm surgesThese are the main form of coastal flooding7. These are mainly caused by high winds pushing water towards coasts. This causes the water to ‘pile up’ causing large waves of up to 8m in some cases8. 1 Roman and Medieval Sea and River Flood defences: English Heritage: 20112 Geographies of UK flooding 2013/14: Physical Geography of the Winter floods: Colin Thorne: Geographical Journal: 20143 RGS Lecture Autumn 2014: Flooding in the UK- myths and realities: Edmund Penning-Rowsell4 Geographies of UK flooding 2013/14: Conclusion: Colin Thorne: Geographical Journal: 20145 National Geographic: Floods: Jim Richardson6 Flooding in England- National assessment of flood risk: 1.1: Environment agency: 20087 Waikato Region Council: Coastal Flooding:8 Hurricane Katrina approaching New Orleans in 2007

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This rise in sea levels is often assisted by low pressures in the centre of the storm causing water levels to rise up by up to 1cm per 1millibar change in pressure9. However these surges are often only able to cause flooding when combined with a high tide, overwhelming flood defences as seen in Figure 1.

Figure 1: Storms and High Tides10

The most devastating example of this to occur in the British Isles was the East Coast flood of 1953. A combination of winds, gusting up to 126mph, and extreme low pressure of 964mb, compared to an average of 1012mb11 led to a storm surge of 5.6m above mean sea level12. 32000 people were evacuated over the course of this disaster with 330 dying across the west coast of England and Scotland and 1800 losing their lives in the low lying Netherlands13. The economic costs were also large with the equivalent (in today’s money) of 1.2 billion pounds worth of damage including the loss of 160000 acres of flooded land unusable for years and infrastructure put out of action such as power stations, roadways and railways14.

2.1.2 TsunamisTsunamis are giant waves created by displacements of water. This can be caused by earthquakes or a large body of material entering the water, such as following a volcanic eruption or large landslide (Figure 2). Whilst in deep oceans the waves may only rise up a few inches however as they reach shallower water the amplitude increases and drag decreases the velocity and they can become walls of water several meters high. On Boxing Day 2004 one of the deadliest tsunamis was created by a 9.0 magnitude earthquake beneath the Indian Ocean. Travelling at 500kph15 and up to 30m in height, it affected 12 countries, taking more than 238000 lives, leaving more than 1.7 million homeless and causing more than $10 9 Met Office: Storm Surge: 201410 Met Office: Storm Surge: 201411 National Oceanography Centre: Storm Surges and Coastal Flooding12 Met Office: 1953 East coast flood- 60 years on: 201413 Met Office: 1953 East coast flood- 60 years on: 201414 Met Office: 1953 East coast flood- 60 years on: 201415 Paul Watson, Barbara Demick and Richard Fausset, Los Angeles Times, January 2, 2005

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Figure 2: How a tsunami occurs

billion in damage16. Although these events can be extremely deadly, as proven above, it is highly unlikely for any major threat to the British Isles. This is due to the lack of subductive tectonic activity within the surrounding areas. With the nearest subduction zone being within the Caribbean, modelling has suggested it would take over 5 hours for any wave to reach British shores and would only be of 1 or 2 meters in height; lower than most storm surges in the region and under the capacity of many flood defences17. This can therefore be dismissed as a major cause of coastal flooding in the UK. 18

2.2 Inland flooding

2.2.1 Pluvial floodingAlthough not as well-known as some other types of flooding, pluvial events can occur without warning and in areas not prone to flooding. Events occur after short, intense downpours, above the capacity of drainage systems or ground infiltration19. This is often aggravated by the reliance of local authorities on Victorian era drainage systems which have deteriorated due to insufficient maintenance20 or are of unsuitable design for current day demands. Victorian-era drains often combine sewage and drainage21 and as a consequence when drains over-flow sewage is brought to the surface, increasing the public health risk and environmental damage.

2.2.2 River (Fluvial) floodingRiver flooding normally occurs when the river cannot cope with the volume of water draining into it from the surrounding land or drainage basin22. This can then lead to overtopping of the river, inundating the areas adjacent to the river channel known as the floodplain, mainly along the lower reaches of the river. This is a natural process that only becomes a risk to human life and property when the floodplain has been subject to development23. Development can also increase the magnitude of floods by increasing surface water run off therefore increasing the flow and speed of the water entering a river channel24. This can be done through deforestation, decreasing interception and transpiration feedback, or urbanisation-where paving means no water is absorbed into the ground leading to more entering the river at a given time25. The over paving of green spaces has increased recently with many households paving over gardens to create driveways with “An area of vegetated garden equivalent to 21 times the size of Hyde park was lost between 1998 and 2006” in London alone26.

16 Phillip Allen Updates conference: Tectonic Hazards17 British Geological survey: Could a Tsunami hit the British Isles: Brian Baptie18 Physorg: Unique Japan tsunami footage boon to scientists: 16th March 201119 Pluvial (rain related) flooding in urban areas- the invisible hazard: Houston et al: JRF Foundation: 201120 Geographies of UK flooding 2013/14: Urban Geography of the Winter floods: Colin Thorne: Geographical Journal: 201421 RGS Lecture Autumn 2014: Flooding in the UK- myths and realities: Edmund Penning-Rowsell22 Environment Agency: Risk of flooding from rivers and seas23 The British Geographer: Floods and River Management24 The British Geographer: Floods and River Management: Human Causes of floods25 The British Geographer: Floods and River Management: Human Causes of floods26 Guardian: London- where the streets are paved with gold, and the gardens with cement: John Vidal: 8 th June 2011

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2.2.3 Groundwater flooding Groundwater flooding occurs when water levels in the ground rises above the surface. It usually occurs in areas underlain by aquifers in permeable rocks. These can be regional and extensive, aquifers, such as chalk or sandstone, or may be more local sand and river gravels underlain by less permeable rocks27.

3 Recent Flood Events in the UK

3.1 2007 Summer FloodsThe summer of 2007 saw rainfall of such high magnitude it’s surpassed any May-July rainfall since 1879 by over 100mm28 (Figure 3). This was due to a series of deep Atlantic depressions that passed over the British Isles. For some areas of Hereford in late June (20th) the 16hour rainfall total reached 134.88mm. This magnitude of storms had a probability of 0.1% of occurring in a given year29. This

caused widespread flooding resulting in a total economic cost of £3.2billion30 and over 55000 homes and businesses affected31. Areas that were significantly affected by the Floods included the Rivers Severn, Thames and Humber. However this cannot cover the total impacts due to the fact the impact on people’s lives and livelihoods, which may take much longer to recover, cannot be expressed in monetary values32. The impact of this flooding was the subject of the 2008 Pitt report that made 92 recommendations as to how the UK could manage floods in the future33. These recommendations form the basis for the 2008 NAFRA paper by the Environment Agency34.

Figure 3: Distribution of rainfall, June35

27 Flooding in England- National assessment of flood risk: 1.1: Environment agency: 200828 The summer 2007 floods in England & Wales- a hydrological appraisal: Marsh & Hannaford: Centre for Ecology and Hydrology: 2007 29 The summer 2007 floods in England & Wales- a hydrological appraisal: Marsh & Hannaford: Centre for Ecology and Hydrology: 200730 The costs of the summer 2007 floods in England: Chatterton et al: Environment Agency: 201031 BBC news: Flooding facts and figures: 6th December 200732 The costs of the summer 2007 floods in England: Chatterton et al: Environment Agency: 201033 2007 floods review: Cabinet Office: 200834 Flooding in England- National assessment of flood risk: 1.1: Environment agency: 200835 Met Office: Heavy rainfall/flooding- June 2007

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3.2 2013/14 Winter FloodsA series of persistent winter storms and heavy rainfall culminating in the wettest January since 176636 (Figure 4), when records began, led to significant flooding across the British Isles including the Somerset Levels and Thames Valley where the majority of media focus was directed. These floods were well documented with the Environment Agency issuing 155 severe flood warnings37.

Fig 4: Distribution of Rainfall Jan 2014 38

3.2.1 CausesThe first major storm to hit the British occurred between the 5-6th December 2013. This was an extreme event causing flooding across Scotland and a storm surge that battered the East coast, exceeding the height of the 1953 storm surge in many areas39. This led to the highest ever tides recorded in the Humber and Thames estuaries40. Another storm on the 18th to 19th of December followed causing more flooding across Northern Ireland and West Scotland41. This was then followed by a significant cluster of storms across Christmas that generated widespread flooding across southern English counties including Dorset and Surrey42. Due to this continued rainfall the ground was already saturated with drainage systems overwhelmed by the time more storms made landfall on New Year’s Eve. When these storms continued into the New Year many riverside towns along the Severn and Thames suffered wide scale flooding43. Additionally the magnitude of these storms coincided with the high spring tide renewing coastal flooding across much of the west coast of the Isles. Although the storms reduced in quantity and magnitude, until the end of January, rainfall continued to put drainage systems under pressure with the wettest January since 177644 (Figure 4). When another 6 storms struck at 2-3 day intervals in early February it renewed the surface water flooding across many areas and also increasing the flooded area on the Somerset levels with 100 cubic

36 Geographies of UK flooding 2013/14: Physical Geography of the Winter floods: Colin Thorne: Geographical Journal: 201437 Winter Floods 2013-14: House of Commons:201438 BBC news: 10 Key moments of the UK winter storms: 17th February 201439 Geographies of UK flooding 2013/14: Physical Geography of the Winter floods: Colin Thorne: Geographical Journal: 201440 Geographies of UK flooding 2013/14: Physical Geography of the Winter floods: Colin Thorne: Geographical Journal: 201441 Geographies of UK flooding 2013/14: Physical Geography of the Winter floods: Colin Thorne: Geographical Journal: 201442 Geographies of UK flooding 2013/14: Physical Geography of the Winter floods: Colin Thorne: Geographical Journal: 201443 Geographies of UK flooding 2013/14: Physical Geography of the Winter floods: Colin Thorne: Geographical Journal: 201444 BBC news: January rainfall breaks records in parts of England: 30 January 2014

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metres of ponded water45 (Figure 5). This rain also caused another outbreak of river flood across much of the Severn and the Thames to a greater extent than the occurrence earlier in the year46. For many though the end of the storms did not signal the end of their troubles as the persistent heavy rain had caused water tables to rise to the highest levels in 179 years in some locations47 -Chilgrove House Well, located on the Upper Chalk outcrops of the South Downs48- causing long duration groundwater flooding into May 201449. There was also large number of sink holes that appeared, including one that appeared within the central reservation of the M2 motorway in Kent50, which could be attributed to high ground water tables and the level of water saturation51.

Although individually these storms and flooding events cannot be ‘regarded as exceptional’ of magnitude as other past events52; the close frequency and the coincident nature of these events caused wide spread impacts over such a continued period of time that meant that these floods had a disproportionate social, political and economic impact.

Figure 5: Flooding Somerset Levels53

3.2.2 Economic ImpactsA popular figure for the average annual losses from flooding floated by the media is £1 billion54 which Penning-Rowsell claims55 are linked to an over estimation of flood losses in the National Assessment of Flood Risk56. Penning-Rowsell believes the annual average loss due to flooding since 1990 is £250 million (adjusted for inflation) and that the winter of 2013/14 was not exceptional in

45 Geographies of UK flooding 2013/14: Physical Geography of the Winter floods: Colin Thorne: Geographical Journal: 201446 Geographies of UK flooding 2013/14: Physical Geography of the Winter floods: Colin Thorne: Geographical Journal: 201447 British Geological Survey: Groundwater flooding in the UK- February 2014: 201448 Encyclopaedia of Hydrology and water resources: Herschy, Reginald W., Fairbridge, Rhodes W.: 199849 Geographies of UK flooding 2013/14: Physical Geography of the Winter floods: Colin Thorne: Geographical Journal: 201450 BBC news: 15ft-deep hole appears on M2 in Kent: 11th February 201451 Geographies of UK flooding 2013/14: Physical Geography of the Winter floods: Colin Thorne: Geographical Journal: 201452 The recent storms and floods in the UK: Slingo et al: Met Office, Centre for Ecology and Hydrology: 201453 Guardian: Floodwaters recede but life still on hold for villagers of Somerset Levels: 16 th March 201454 Guardian: UK flood clean-up cost could hit £1 billion, insurance experts warn: Hilary Osborne: 20 th February 201455 RGS Lecture Autumn 2014: Flooding in the UK- myths and realities: Edmund Penning-Rowsell56 Flooding in England- National assessment of flood risk: Environment agency: 2008

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comparison as losses to the nation are expected to reach £290 million57. This can be linked to the small number of homes (7800) and businesses (3200) affected58 compared to 55000 in 200759. In part this impact can be attributed to the success of engineering methods of flood protection such as the installation of demountable flood barriers at key locations on the River Severn60.

3.2.3 Social impactsWith many arguing that the blame lies with those who choose to live and work in these areas of risk, there is increasing pressure on developers, insurers and local authorities to reduce the level of development on flood plains; areas that are naturally designed to flood61. However it should be noted that development on flood plains is slowing62 and that it in almost 100% of cases the advice of the Environment Agency on development in these areas is followed63. However, it could be noted that this slowdown in development may be merely a reflection of nationwide property development trends following the recession64.

Whilst many understand the physical health implications of flooding less understand the mental health issues that may occur following a prolonged and intense period of flooding such as 2013/14. Penning-Rowsell argues that while the physical impacts, such as respiratory problems from the damp, reduce exponentially to almost none 2 years after the floods; mental health issue continue on for much longer65. They are hard to understand and treat and are often not the issue at the forefront of peoples mind and therefore not much is done to combat the issue in the aftermath of a flood.

3.2.4 Political impactsThorne believes that the management of flood risk and development largely depend on public opinion66 and this is agreed, in principle by Ball and Green. They believe that widespread flooding, such as 2013/14, can lead to public outcry towards either politicians, fuelling an increase in spending on defences, or towards people who choose to live or work in areas subject to flood risk claiming they should learn to live with it67 or be prepared to move. This occurred quite neatly post the 2013/4 floods with one group blaming those who were victim of the flooding, who should of known that they were living or moving into a high risk area, and another blaming the Environment Agency and government68. With National newspapers often coming out in support of those flooded with

57 The 2013/14 floods: what do they tell us about the overall flood risk in England and Wales: Edmund Penning-Rowsell: 201458 Geographies of UK flooding 2013/14: Social Geography of the Winter floods: Colin Thorne: Geographical Journal: 201459 See ‘3 2007- A comparison’60 RGS Lecture Autumn 2014: Flooding in the UK- myths and realities: Edmund Penning-Rowsell61 Geographies of UK flooding 2013/14: Social Geography of the Winter floods: Colin Thorne: Geographical Journal: 201462 Geographies of UK flooding 2013/14: Social Geography of the Winter floods: Colin Thorne: Geographical Journal: 201463 RGS Lecture Autumn 2014: Flooding in the UK- myths and realities: Edmund Penning-Rowsell64 Housing and economic linkages: 4.2 The international impact of the recession on housing: Kamm and Chivunga: Chartered Institute of Housing: 201065 RGS Lecture Autumn 2014: Flooding in the UK- myths and realities: Edmund Penning-Rowsell66 Geographies of UK flooding 2013/14: Political Geography of the Winter floods: Colin Thorne: Geographical Journal: 201467 Future flooding and coastal erosion risks: Human behaviour: (section by) Ball and Green: Thomas Telford London: 201468 Geographies of UK flooding 2013/14: Political Geography of the Winter floods: Colin Thorne: Geographical Journal: 2014

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headlines such as “EA bosses… refuse £1.7 million dredging of key Somerset rivers that could have stopped flooding”69 politicians have appeared to react in favour of saving face rather than addressing major long term problems. David Cameron, the Prime Minister, criticised his own Cabinet Minister in charge of Environment, food and rural affairs: Owen Patterson and the chair of the Environment Agency, Lord Smith for discontinuing dredging in the late 1990s70.

“From the late 1990s – far too long – the Environment Agency believed that it was wrong to dredge. Those of us with rural constituencies

affected by flooding have seen the effectiveness of some dredging.”71 David Cameron

“Now if it is good for some places, we need to make the argument that it would be good for many more places. I have said that we are going to

see dredging on the [rivers] Tone and the Parrett in the Somerset Levels because that would make a difference. But I believe it is time for Natural England, the Environment Agency and the departments to sit round the table and work out a new approach that will make sure that something that did work, frankly, for centuries is reintroduced.”72 David Cameron

This led to Cameron pledging to start dredging before the 1st of April as long as the ground was able to support the weight of machinery (started 29th March 2014)73.

69 Daily Mail: EA bosses spent £2.4 million on PR… refuse £1.7 million dredging of key Somerset rivers that could have stopped flooding: 10 February 201470 Geographies of UK flooding 2013/14: Pointing the finger- flooding and river management: Colin Thorne: Geographical Journal: 201471 Independent: David Cameron overrules Environment Secretary Owen Paterson to order urgent dredging in Somerset to combat the flooding: Tom Bawden: 5th February 201472 Independent: David Cameron overrules Environment Secretary Owen Paterson to order urgent dredging in Somerset to combat the flooding: Tom Bawden: 5th February 201473 BBC news: Somerset floods- River dredging begins on Parrett and Tone: 31st March 2014

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4 Future

744.1 Why flood impacts will increaseFigure 6 summarises the why the risk and likelihood of flooding may increase in the future. More detailed analysis highlights a variety of potential causes.

74 Flooding in England- National assessment of flood risk: 1.1: Environment agency: 2008

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Figure 6: Aspects of Flood Risk

4.1.1Climate changesWhile not an immediate threat climate change has the potential to greatly increase the frequency and occurrence of flooding in the British Isles through rising sea levels and increased rainfall75. Sea levels have been rising ‘at a rate greater than the mean rate of the past two millennia’ since the mid-19th century76. Rising 0.19m (+/- 0.02m) between 1901 and 201077. Increasing global temperatures are projected to continue this rate of rise to a height above current levels between 0.52 to 0.98m by 210078 for RCP8.5 (Representative Concentration Pathway)79 . RCP8.5 is the highest emission prediction with CO2 emissions modelled to rise fourfold80. Whilst sea levels are rising globally, locally the impacts may vary. In the UK this is largely due to isostactic rebound, a post-glacial phenomena caused by the disappearance of the glacial ice cover. During and subsequent to the ice melt, as has occurred in North West Scotland since the last ice age 12000 years ago81, the land has experienced uplift and therefore relatively lower sea levels. Rebound has been differential across the British Isles with evidence of relative subsidence in the southern UK causing local sea level increases. 82

There has been a notable rise in periods of heavy rainfall falling on the British Isles in the past half century83; the frequency of heavy rainfall has been fluctuating between 1-in-75 days and 1-in-100 days since 2000. In comparison the 5 year running mean between 1970 and 1980 did not break 1-in-100 days and fluctuated to as low as 1-in-125 days84. These changes could be down to many natural factors. Sea surface temperatures have increased by 0.85°C85 and it is “extremely likely that more than half the observed global average surface temperature rise from 1951 to 2010 was caused by anthropogenic86 increase in greenhouse gas concentrations87. It has been suggested that rainfall increases in relation to temperature could exceed the simple

75 RGS Lecture Autumn 2014: Flooding in the UK- myths and realities: Edmund Penning-Rowsell76 IPCC AR5 SMP: B4: 201477 IPCC AR5 SMP: B4: 201478 IPCC AR5 SMP: E6: 201479 World Meteorological Organization: Emission Scenarios80 RCP8.5-A scenario of comparatively high greenhouse gas emissions : Keywan, Riahi, et al: 201181 Science Museum: Past Climate- Ice ages82 The first global warming refugees: Wilson: 200283 Met Office: Statistics for December and 2012- is the UK getting wetter: 201384 The recent storms and floods in the UK: Has climate change been a contributing factor?: Met Office, Centre for Ecology and Hydrology: 201485 IPCC AR5 SMP:B1: 201486 Adj. “caused by humans”87 IPCC AR5 SMP:D3: 2014

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Figure 7: Isostatic Rebound in the UK

thermodynamic Clausius-Clapeyron relationship (6-7% increase per 1°C)88. These changes in sea surface temperature and the spatial patterns within oceans lead to spatial differences in precipitation levels89; yet more research is needed to fully determine the complete impact of these changes90.

With global temperature and sea levels set to rise, alongside the magnitude and frequency of hydro-metrological hazards for high latitude North Atlantic91, flooding could become ever more significant in shaping Britons lives. This means the ways we can manage floods are becoming ever more important in the political spectrum92 and to communities of all scales.

4.1.2 Urbanisation and population growthWith the 82% of the United Kingdom’s population living in urban areas, up from 79% in 2000, there is a growing concern over the number of people affected by floods 93. Continuing development on floodplains, due to the historical location of many urban areas, has contributed to the rapidly rising economic costs of flood events in the UK94. Heavily urbanised areas can also increase the magnitude of floods as permeable areas are replaced by impermeable paving, accelerating run off (Figure 8) 95.

4.2 What can we do to defend ourselves?Whilst flood defences are needed they must be well planned and assessed to ensure they can be sustainable and cost effective. The risk after a major event such as the winter 2013/14 is that many of the decisions made post event can be reactive rather than proactive in ensuring future risk is

88 The recent storms and floods in the UK: Has climate change been a contributing factor?: Met Office, Centre for Ecology and Hydrology: 201489 The recent storms and floods in the UK: Has climate change been a contributing factor?: Met Office, Centre for Ecology and Hydrology: 201490 Global Warming Pattern Forming: Sea Surface Temperature and Rainfall: Xie et al: University of Hawaii at Manoa, National Center for Atmospheric research, Geophysical Fluid Dynamics Laboratory: 200991 Trends and low frequency variability of extra-tropical cyclone activity in theensemble of twentieth century reanalysis: Wang et al: 201292 See ‘3.2.4 Political Impacts’93 World Bank: Urban population: 201494 The summer 2007 floods in England & Wales- a hydrological appraisal: Flood risk and vulnerability: Marsh & Hannaford: Centre for Ecology and Hydrology: 200795 Effects of Urban development on floods: Konrad: USGS:2014

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Figure 8: Impact of Development on Runoff

minimised96. An example of this would be David Cameron’s decision to overrule the Environment Agency and restart dredging along the rivers Tone and Parrett on the Somerset levels97.

4.2.1 Engineering flood control

Flood defences and embankments

Flood walls and embankments offer a similar but have different requirements. Flood walls are effectively a wall built to protect areas at risk from flooding (Figure 9). Whilst this is their primary aim they can also be used to improve the aesthetic appearance of the area, such as the Perth flood alleviation scheme98. This is similarly the case with embankments; however these are mounds of natural material raised to the design crest level and can require a much larger footprint than a floodwall99. Another possibility is the deployment of temporary and demountable defences when and where they are needed100

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Figure 9: Flood Walls and Embankments

96 RGS Lecture Autumn 2014: Flooding in the UK- myths and realities: Edmund Penning-Rowsell97 See ‘3.3.4 Political Impacts’98 Flood walls and flood embankments: 9.2: Rickard: 200999 Flood walls and flood embankments: 9.4: Rickard: 2009100 Flood walls and flood embankments: 9.1: Rickard: 2009101 Flood walls and flood embankments: 9.3: Rickard: 2009

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Coastal barriers

Britain has one of the largest moveable flood barriers in the world spanning 540m across the mouth of the River Thames102(Figure 10). It closes to protect London from coastal storm surges but also from fluvial flooding further upstream103. In 2014 it was operated a record number of times, 48, beating the previous record of 19 (2003) by some margin104.

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Figure 10: Thames Barrier

4.2.2 DredgingDredging is a controversial issue with conflict coming between many fluvial analysts and locals. It is the process of removing sediment from the river channel, either from the bed or the sides, to increase the conveyance capacity of the river channel106. By increasing the conveyance capacity the aim is to increase the bankfull discharge which in turn should not only reduce the amount of overbank flooding but also increase the rate at which any flood waters are dispersed (Figure 11).

107

Figure 11: How Dredging Works

102 GOV.UK: Thames Barrier: 2014103 GOV.UK: Thames Barrier: 2014104 GOV.UK: Thames Barrier: 2014105 Telegraph: Thames floods- Thames Barrier closed for record 19th consecutive tide: 16th February 2014106 Floods and Dredging- a reality check: 2.1: Chartered Institution of Water and Environmental Management: 2014107 BBC news: How do you stop flooding: 29th January 2014

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4.2.3 Natural Flood Management TechniquesNatural flood management may be promoted by (Figure 12):

Storing water: This can be done by maintaining the capacity of ponds, ditches and reservoirs or creating new storage areas108. Water meadows are an example of this. They are areas of land deliberately allowed to flood then entrapped so that water is taken away from swollen rivers109

Slowing water: This is achieved by increasing its resistance to flow; examples include contour planting of trees either on riverbanks or the wider floodplain110.

Reducing flow connectivity: Interrupting surface flows of water can be integrated into either option above. Water storage areas or buffer strips of grass and/or trees can take away a pathway of flow111

Sustainable Urban Drainage systems (SUDS): These look at both past and future infrastructure. Thorne describes the need to replace the Victorian drainage system where sewage and drainage is contained in one channel which cannot cope with the current and future demands placed upon it in heavy rainfall events112. Another option is to use permeable paving113 and increase green areas that allow infiltration and transpiration to reduce runoff to morph the urban hydrological cycle to become more like the natural cycle114.

Figure 12: Flood Mitigation Techniques

108 Natural Flood management: Houses of Parliament: 2011109 RGS Lecture Autumn 2014: Flooding in the UK- myths and realities: Edmund Penning-Rowsell110 RGS Lecture Autumn 2014: Flooding in the UK- myths and realities: Edmund Penning-Rowsell111 Natural Flood management: Houses of Parliament: 2011112 Geographies of UK flooding 2013/14: Urban geography of the winter floods: Colin Thorne: Geographical Journal: 2014113 RGS Lecture Autumn 2014: Flooding in the UK- myths and realities: Edmund Penning-Rowsell114 Geographies of UK flooding 2013/14: Conclusion: Colin Thorne: Geographical Journal: 2014

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4.2.4 Planning policy Planning policy can play a significant role in reducing the future impacts of floods by restricting development in high risk areas. The Environment Agency advises local authorities on risk of flooding and makes recommendations on planning permission through NAFRA115 this included a large scale mapping of flood risk areas for use by planners, developers, insurers and the general public to increase awareness. In almost all known cases this advice has been followed; however the majority of cases there is not the information on whether the advice has been taken or not116. Thorne argues that Flood-Re, a reinsurance fund to protect insurers from widespread losses after flood events117, could assist in slowing development on flood plains as it has the potential to provide cover for existing properties yet could discourage new, inappropriate developments118.

4.3 Evaluation of approaches to Flood Management

Whilst there were some dramatic pictures of houses inundated with water following the 2013/14 floods the reality was that the impacts, given the magnitude of the total event, was very limited119. World class flood defences such as the Thames Barrier and the lessons learnt from past events, such as such 2007, led to 3 million properties being protected; a significant increase on the 100,000 in 2007120. An example of an effective and cost effective approach has been the use of demountable flood barrier in urban areas along the Severn Valley (Figure 13). However the Thames Barrier has been closed a record number of times in 2014121 and is argued it may be time for a replacement to continue to protect the£200 billion worth of assets sitting on the banks of the Thames122.

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Figure 13: Demountable Flood Barrier, Worcestershire

115 See ‘3.2.2 Economic Impacts’116 RGS Lecture Autumn 2014: Flooding in the UK- myths and realities: Edmund Penning-Rowsell117 Flood-Re explained: Association of British Insurers:2014118 Geographies of UK flooding 2013/14: Social geography of the winter floods: Colin Thorne: Geographical Journal: 2014119 Geographies of UK flooding 2013/14: Physical geography of the winter floods: Colin Thorne: Geographical Journal: 2014120 Winter Floods 2013-14: House of Commons:2014121 See ‘4.3.1 Engineering flood defences’122 The Telegraph: The Thames Barrier has saved London- but is it time for TB2: 18th February 2014123 Local Government Association: Floods and erosion risk management: 2013

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However whilst increased protection is not often seen as a bad thing, there are some potential pitfalls. Penning-Rowsell argues that as protection increases the sense of safety increases in parallel leading to more development and therefore more property at risk. This can set off long term cycle where more development leads to the need for better defences and vice versa124.

While SUDS and upland catchment management have proven to be effective at small scales they will not significantly reduce the impacts of a high magnitude, long scale event such as the 2013/14 floods125. Wide spread use may have the potential to reduce impacts but this has yet to be proven.

Dredging will only have a limited effect on conveyance of the channel unless the whole length is dredged. Even then any major flood will have a peak flow many times greater than the bankfull discharge and then will overtop the sides flooding the surrounding floodplain126. It is an extremely expensive operation, costing £6 million for the 8km stretch of the Tone and Parrett127; and must be repeated as material from upstream will re-accumulate over span of 5-10 years128, which has been cited as the reason it was ceased in the first place129. Dredging in tidal river areas will have little- to no positive impact as the water level is determined by the global sea level. It will also increase the ease of which tidal flows and sediments can flow up the river; this has a potential to increase the risk from storm surges130.

Another potential impact of dredging is an increase in conveyance without increasing capacity. This will increase flow velocity and therefore heighten the flood risk downstream as peak flows are not slowed upstream due to canalisation131

5 Recommendations

5.1 General RecommendationsWith trends showing an increasing frequency and magnitude of future storm events, investment into flood defences and mitigation must be continued in the context of an increasing population and pressure of development for housing. However significant additional investment into flood defences is unfortunately very unlikely. This is because of the opportunity cost of moving funds from more immediately obvious funding areas such as schools or the NHS which may lead to public disproval in a time when politicians will do anything to win votes. This has led to cuts for funding for LLFA’s by a third for 2015/16132 and an overall fall in flood defence spending by 10% since the previous government, excluding emergency disaster relief, leaving more than half the UKs flood defences with minimal maintenance133. These cuts occur in the face of evidence of the significant cost benefit 124 RGS Lecture Autumn 2014: Flooding in the UK- myths and realities: Edmund Penning-Rowsell125 RGS Lecture Autumn 2014: Flooding in the UK- myths and realities: Edmund Penning-Rowsell126 Floods and Dredging- a reality check: 2.1: Chartered Institution of Water and Environmental Management: 2014127 Waste and wastewater treatment: EA completes dredging of the Somerset Levels rivers: 3rd November 2014128 Floods and Dredging- a reality check: 2.1:Chartered Institution of Water and Environmental Management: 2014129 Geographies of UK flooding 2013/14: Pointing the finger: Colin Thorne: Geographical Journal: 2014130 Geographies of UK flooding 2013/14: Pointing the finger: Colin Thorne: Geographical Journal: 2014131 Floods and Dredging- a reality check: 2.4:Chartered Institution of Water and Environmental Management: 2014132 Guardian: Local Authority flood defence funding cut by a third next year: 19th November 2014133 Guardian: Risks of floods in England up due to cuts in Government funding, say NAO: 5th November 2014

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of investing in flood and coastal erosion risk management has a cost benefit averaging better than 1 to 8134.

On a large scale, for the magnitude of storms we face in the British Isles, hard engineering techniques are the most likely to succeed in the long term: Examples include the Thames and Humber Barriers. However this may not be the most suitable in all parts of the country and it requires significant research to understand what methods will give the best value in times where government cuts are continuing. This is because the social impact of any flooding must be taken into account alongside the more obvious economic costs.

To best protect the British Isles from significant losses in future years an integrated, proactive response is needed. This not only involves central and local governments but also the private sector and the community at risk. There needs to be a long term, ring-fenced funding for flood and erosion risk management. This protection from change in administrations would allow the smoothest and most efficient running of the long term continuous projects that are required to protect the British Isles. The response and decision on how best to protect areas must be influenced by both top-down and bottom-up approaches. Advice must be sought from leading expert organisations such as The Environment Agency and the Flood Hazard Research Centre at Middlesex University. Also it is important for residents to be consulted and informed of plans. The government and private sector also have a responsibility to change the social mind-set of development on flood plains. Firms such as Flood-Re have the ability to make clear to developers of the risk and added cost of developing these at-risk areas. Whilst engineering advances can do so much to protect the homes and businesses’ there is a limitation. To fully attempt to minimise flood risks we must challenge the social mind-set. We must remove the thinking that ‘this won’t happen to me’. We must educate the population so they can make their own fully informed decisions on whether to take that significant risk in developing and living in these areas. In this onus must fall on the government to provide this education of not only those currently living in high risk areas but the entire population.

5.2 Approaches to Flood Prevention in Study AreasDifferent approaches should be adopted in the two areas:

5.2.1 SomersetThe Somerset levels (Figure 14) have a low value in terms of economic loss with a sparse population. The compensation handed out to farmers for agricultural losses only reached the 10s of millions135 and therefore to completely mitigate this low lying area would be an inefficient use of money and resources. This is a prime example of where upland catchment management may be a more effective method. Whilst it may not alleviate flooding in these areas it may help to slow surface runoff therefore reducing the pressure on flood defences further downstream in population areas such as Bridgwater. Another

134 UK climate change risk assessment-government report: HM Government: 2012135 What do the 2013/14 floods tell us about overall flood risk in England and Wales?: Penning-Rowsell: 2014

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Figure 14: Somerset Levels

possible solution that has been suggested is a tidal barrier at the mouth of the River Parrett as recommended in the Bridgwater Strategic Flood Defence Infrastructure Planning although this would not be needed until at least 2030136. This barrier would operate on a similar basis to the Thames barrier and be used to resist high tides and storm surges from travelling upstream.

5.2.2 Thames BasinThe Thames is an area that justifies the use of hard engineering defences. The significantly higher population (5th of the UKs population137) and economic value lying within the Thames catchment area relies on it. Whilst the Thames Barrier currently does an outstanding job protecting London’s residents from storm surges and high tides there is a need to replace it sooner rather than later as sea levels rise. Further upstream in the Runnymede, Walton and Teddington areas, where the majority of affected properties were in 2013/14, it would be beneficial to re-engineer weirs to improve capacity and create flood channels to divert water away from populated areas (Figure 15)138. However these areas also require an integrated response with increased planning controls on floodplain development, the use of sustainable urban drainage further upstream, wider spread use of permeable paving to slow surface run off and the creation of flood basins that would attenuate flood peaks by storing water on the floodplain.

Figure 15: Lower Thames Flood Management Proposals

136 Bridgwater Strategic Flood Defence Infrastructure Planning- Final Report: Environment Agency, Sedgemoor District Council: 2009137 The river Thames Initiative- why monitor river catchment: Centre for Ecology and Hydrology138 Lower Thames Flood Risk Management Strategy: Environment Agency: 2010

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Summary of References Used

These are referenced in full as Footnotes to the text.

LECTURE:Flooding- myths and realities: Edmund Penning-Rowsell

LECTURE: Presentation of the IPCC 5th installment: Dr David Adger

LECTURE: Tectonic Hazards: Stewart et al: Phillip Allen Updates

WEB: Met Office

WEB: Guardian

WEB: Daily Mail

WEB: Independent

WEB: BBC news

WEB: National Geogrphic

WEB: Waikato region council

WEB: National Oceanography Center

WEB: Los Angeles Time

WEB: British Geological Survey

WEB: World Meteorological Organization

WEB: Science Museum

WEB: World Bank

WEB: GOV.UK

WEB: Telegraph

WEB: Water and Wastewater treatment

PAPER: IPCC Ar5: Summary for Policy-Makers: 2014

PAPER:Geographies of UK flooding 2013/14: Colin Thorne: Geographical Journal: 2014

PAPER: Future flooding and coastal erosion risks: Thorne et al: 2014

PAPER: Global Warming Pattern Forming: Xie et al: University of Hawaii at Manoa, National Center for Atmospheric research, Geophysical Fluid Dynamics Laboratory: 2009

PAPER: A global perspective on storms and floods in the UK: Slingo et al: Met Office: 2014

PAPER: National assessment of flood risk: Environment Agency: 2009

PAPER: Housing and economic linkages: Kamm and Chivunga: Chartered Institute of Housing: 2010

PAPER: Flooding in England- National assessment of flood risk: Environment Agency: 2008

PAPER: RCP8.5-A scenario of comparatively high greenhouse gas emissions : Keywan, Riahi, et al: 2011

PAPER: The first global warming refugees: Wilson: 2002

PAPER: The recent storms and floods in the UK: Met Office, Centre for Ecology and Hydrology: 2014

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PAPER: Trends and low frequency variability of extra-tropical cyclone activity in the ensemble of twentieth century reanalysis: Wang et al: 2012

PAPER: The summer 2007 floods in England & Wales- a hydrological appraisal: Flood risk and vulnerability: Marsh & Hannaford: Centre for Ecology and Hydrology: 2007

PAPER: Effects of Urban development on floods: Konrad: USGS:2014

PAPER: Flood walls and flood embankments: Rickard: 2009

PAPER: Floods and Dredging- a reality check: Chartered Institution of Water and Environmental Management: 2014

PAPER: Natural Flood management: Houses of Parliament: 2011

PAPER: Flood-Re explained: Association of British Insurers:2014

PAPER: Winter Floods 2013-14: House of Commons:2014

PAPER: Local Government Association: Floods and erosion risk management: 2013

PAPER: UK climate change risk assessment-government report: HM Government: 2012

PAPER: What do the 2013/14 floods tell us about overall flood risk in England and Wales?: Penning-Rowsell: 2014

PAPER: Bridgwater Strategic Flood Defence Infrastructure Planning- Final Report: Environment Agency, Sedgemoor District Council: 2009

PAPER: The river Thames Initiative- why monitor river catchment: Centre for Ecology and Hydrology

PAPER: Lower Thames Flood Risk Management Strategy: Environment Agency: 2010.

Word Count = 5027

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