tag:theconversation.com,2011:/global/topics/uk-storm-surge-8516/articlesUK storm surge – The Conversation2024-01-23T17:30:34Ztag:theconversation.com,2011:article/2214412024-01-23T17:30:34Z2024-01-23T17:30:34ZBritain is at bursting point and its flood barriers need to be updated<figure><img src="https://images.theconversation.com/files/570133/original/file-20240118-29-picje5.JPG?ixlib=rb-1.1.0&rect=0%2C0%2C1617%2C1076&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The Thames Barrier is already being used far more than was originally intended.</span> <span class="attribution"><span class="source">Sunke Trace-Kleeberg</span></span></figcaption></figure><p>Flooding is the top environmental hazard identified in the UK’s <a href="https://www.gov.uk/government/publications/national-risk-register-2023">National Risk Register</a>, after a pandemic. Around one in six homes are currently at risk of flooding – a value likely to increase.</p>
<p>Many floods are caused by unusually high rainfall from successive storms which lead to <a href="https://theconversation.com/storm-babet-caused-dangerous-floods-as-the-dry-side-of-scotland-isnt-used-to-such-torrential-rain-216103">saturated ground</a> and then flooding. But flooding can also occur when high tides combine with strong winds that blow water towards the coast, resulting in extremely high water levels along the seaside and into estuaries.</p>
<p>This form of flooding happens less frequently, but is no less dangerous. In 1953 one of these “storm surges” killed more than 300 people along the east coast of Britain – it remains the country’s <a href="https://theconversation.com/1953-storm-surge-how-britains-worst-natural-disaster-kicked-off-the-debate-on-climate-change-71310">worst ever natural disaster</a>. A similar surge struck during <a href="https://www.surgewatch.org/events/1/">Storm Xaver</a> in December 2013 but thanks to better flood defences, forecasts and warnings, there was no repeat of the 1953 damage.</p>
<p>One way the UK can respond to the growing risk these coastal floods, particularly in estuaries, is to build storm surge barriers. These are enormous metal and concrete structures with movable gates that can be closed temporarily to hold back storms and high tides, protecting people and property behind from coastal flooding. </p>
<p>There are four main storm surge barriers in the UK: Thames, Ipswich, Hull and Boston, alongside many smaller barriers. This network of defences reduces the risk for millions of people and helps protect billions of pounds worth of infrastructure. Completed in 1982, the Thames barrier in London is one of the world’s largest movable flood barriers shielding 125 square kilometres of central London and 1.42 million people.</p>
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<a href="https://images.theconversation.com/files/570146/original/file-20240118-23-aehxwa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Barrier structure above river" src="https://images.theconversation.com/files/570146/original/file-20240118-23-aehxwa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/570146/original/file-20240118-23-aehxwa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/570146/original/file-20240118-23-aehxwa.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/570146/original/file-20240118-23-aehxwa.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/570146/original/file-20240118-23-aehxwa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/570146/original/file-20240118-23-aehxwa.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/570146/original/file-20240118-23-aehxwa.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Hull’s tidal flood barrier is the UK’s second largest.</span>
<span class="attribution"><span class="source">Simon Annable / shutterstock</span></span>
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<p>Like cars, movable flood barriers need regular servicing to ensure all systems are working properly to allow them to close smoothly when needed. This means that there is a limit to the number of occasions flood barriers can close in a year while still allowing enough time for maintenance work. </p>
<p>That isn’t a problem when the barrier is rarely being used, the Thames Barrier only closed eight times in <a href="https://www.theguardian.com/environment/2023/jun/30/before-the-flood-how-much-longer-will-the-thames-barrier-protect-london">the entire 1980s</a>. But in the record-breaking stormy winter of 2013/2014 it closed 50 times, equal to the maintenance limit. This is part of a trend driven by climate change: as sea-levels rise and storms get stronger, movable flood barriers are going to be called into action more often. This means more work will be needed to look after them with less time to carry out that work. </p>
<h2>Learning with the Dutch</h2>
<p>A country that is experiencing this challenge is the Netherlands. The Dutch are particularly vulnerable to flooding as the country is densely populated and 45% of its land lies below sea level. </p>
<p>The same 1953 storm that flooded the UK was even more devastating in the Netherlands, taking the lives of 1,836 people and causing €5.4 billion (£4.62 billion) worth of damage (in today’s money). This led the government to transform the country’s flood protection including the construction of six movable flood barriers with the world’s oldest – <a href="https://www.rijkswaterstaat.nl/water/waterbeheer/bescherming-tegen-het-water/waterkeringen/deltawerken/hollandsche-ijsselkering">Hollandsche IJssel</a>, completed in 1958 – and largest automatic – <a href="https://www.rijkswaterstaat.nl/en/projects/iconic-structures/maeslant-barrier">Maeslant</a> barrier, completed in 1997. </p>
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<a href="https://images.theconversation.com/files/570136/original/file-20240118-15-la2c24.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Barrier across canal seen from above" src="https://images.theconversation.com/files/570136/original/file-20240118-15-la2c24.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/570136/original/file-20240118-15-la2c24.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/570136/original/file-20240118-15-la2c24.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/570136/original/file-20240118-15-la2c24.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/570136/original/file-20240118-15-la2c24.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/570136/original/file-20240118-15-la2c24.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/570136/original/file-20240118-15-la2c24.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">The Maeslant barrier protects Rotterdam and its huge port from floods.</span>
<span class="attribution"><span class="source">Faysal06 / shutterstock</span></span>
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<p>The Dutch have a wealth of knowledge and experience in flood protection. This expertise is shared internationally through collaboration facilitated by <a href="https://www.i-storm.org">I-STORM</a>, an international network connecting and sharing knowledge between people working with movable flood barriers around the world.</p>
<p>But even in the Netherlands things need to be changed. We recently published <a href="https://www.sciencedirect.com/science/article/pii/S0378383923000601">research on the Maeslant barrier</a> which revealed that although it has only closed once in its 26-year lifetime, on <a href="https://www.netherlandswaterpartnership.com/news/maeslant-storm-surge-barrier-largest-moveable-object-world-was-closed-last-night-first-time">December 21 2023</a>, the amount of work needed to keep the barrier functioning is increasing and no longer fits into the summer maintenance period. This makes it difficult to achieve the safety standards required by law. Without changes to the way the barrier is looked after, it will not reach its planned lifetime and will not keep up with rising sea levels. </p>
<h2>Heading into an uncertain future</h2>
<p>Back in the UK, new movable flood defences are being built across Britain to protect more people and properties. The <a href="https://waterprojectsonline.com/custom_case_study/boston-barrier-2021/">Boston barrier in Lincolnshire</a> became operational in 2021 to increase flood protection for 14,300 properties. And work has begun on a new barrier in <a href="https://www.somerset.gov.uk/beaches-ports-and-flooding/bridgwater-tidal-barrier/">Bridgwater, Somerset</a> designed to protect 13,000 homes and businesses.</p>
<p>Plans are also underway to replace existing barriers. For instance, the government’s <a href="https://www.gov.uk/government/collections/thames-estuary-2100-te2100">Thames Estuary 2100</a> plan estimates that the Thames barrier will reach the end of its life in 2070. Further sea level rise will mean the barrier closes with increasing frequency making it harder to maintain, holding up ship traffic, and harming the health of the river. Although this is more than 40 years away, work has already begun planning a new movable flood defence to continue keeping high tides out of London. </p>
<p>This forward planning has put the UK on the front foot and keeps it resilient to the risks posed by sea-level rise, changing climate and coastal flooding. But, with more devastating weather records being broken each passing year, and the ever present threat of climate change bearing down on us, it is likely that flood barriers and coastal defences will become more important as we head into an uncertain future.</p>
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<img alt="Imagine weekly climate newsletter" src="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p class="fine-print"><em><span>Sunke Trace-Kleeberg's PhD is funded by the Natural Environment Research Council (NERC), Rijkswaterstaat, Southampton Marine and Maritime Institute (SMMI) and the Environment Agency (EA).</span></em></p><p class="fine-print"><em><span>Ivan Haigh receives funding from the Natural Environment Research Council (NERC), Rijkswaterstaat and the Environment Agency (EA).</span></em></p>As the sea rises and storms get stronger, movable flood barriers are going to be used more often.Sunke Trace-Kleeberg, Postgraduate researcher, University of SouthamptonIvan Haigh, Professor in sea level and flooding, University of SouthamptonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/713102017-01-16T15:12:43Z2017-01-16T15:12:43Z1953 storm surge: how Britain’s worst natural disaster kicked off the debate on climate change<p>Towns and villages along the east coast of England were put on red alert on Friday 13 January. A combination of strong winds and high tides led to fears a “storm surge” would wash over flood defences, and residents of Great Yarmouth, Norfolk and Jaywick, in Essex, were among those ordered to evacuate. </p>
<p>In the end, the <a href="http://www.bbc.co.uk/news/uk-england-38619611">worst was avoided</a>. The winds, tides and waves didn’t quite combine to cause serious flooding, and people have returned home. But this was not the first time the region had been threatened with inundation, and the flood defences that held firm in 2017 were largely built in response to a previous, more deadly, storm surge.</p>
<p>The worst natural disaster in modern British history occurred on the night of January 31, 1953. A tidal surge caused the North Sea to rise up to five metres above its average level, which led to widespread flooding along the east coast of Britain, particularly south of Yorkshire. Some 30,000 people were evacuated, 1,000 square kilometres of land was inundated, and <a href="http://www.metoffice.gov.uk/news/in-depth/1953-east-coast-flood">307 people in England and 19 people in Scotland died</a>. The death toll was particularly bad on Canvey Island in the Thames Estuary. </p>
<p>In the low-lying Netherlands the consequences were much greater – more than 1,800 deaths. Soon after, the Dutch began to construct their huge and very costly system of <a href="https://www.eh-resources.org/dutch-river-defences-in-historical-perspective/">flood defences</a>.</p>
<p>The response in Britain was less decisive. Former chancellor and home secretary Viscount Waverley oversaw an inquiry, publishing a very effective <a href="http://discovery.nationalarchives.gov.uk/details/r/C5004609">report</a> later that year. Waverley sought expert opinion on how best to renew flood defences and his recommendations included the creation of a new early warning system, quickly established, and the construction of a retractable barrier to protect London.</p>
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<p>The long political machinations that eventually led to the passage of the 1972 Thames Barrier Act are fascinating in themselves, but what is more immediately arresting is the explanation Waverley offered for the tidal surge itself. For the first time, Waverley’s report made climate change a concern of government.</p>
<h2>What caused the storm surge</h2>
<p>Waverley explained that the flooding was caused by a combination of factors. Strong northerly winds coming in off the Atlantic coincided with a relatively high tide, thereby forcing an unusually large quantity of water down the narrowing north-south axis of the North Sea to the bottleneck at the Straits of Dover. The rotation of the earth ensured that the water was deflected to the west of the tidal currents, thereby hitting the east coast of Britain. A significant quantity of excess water was forced up the Thames Estuary, threatening to spill over London’s flood defences. </p>
<p>Waverley was at pains to point out that the high tide and the surge were distinct phenomena. Had the surge occurred at low tide, its effect would have been little noticed. Also, inland rainfall had been below average. Had east coast rivers been at their strongest, the destruction caused by the tidal surge would have been much greater, causing significant loss of life and damage to the capital’s infrastructure. Indeed, the risk to the London Underground conditioned much of the debate that followed.</p>
<p>The data presented to Waverley suggested that floods like January 1953 were becoming more frequent and that the combination of factors that produced them were likely to happen more often. There were three reasons for this. First, water levels were rising. By the 1950s scientists had known for a generation or so that the climate had been warming for a century, and that this was causing glaciers to melt.</p>
<p>Second, the phenomenon of tilt: the north-west and north of England was gradually rising and the south-east was gradually sinking – or downwarping – a notion that had some popular traction, especially in East Anglia. Downwarping compounded the effect of higher water levels and was also caused by climate change. At the end of the last ice age, glaciation had reached as far south as the line from the Bristol Channel to the Wash. With the weight of ice no longer acting on northern Britain, a gradual correction was taking place – and <a href="https://www.dur.ac.uk/news/newsitem/?itemno=8805">continues to</a>. </p>
<p>Third, was the idea that changing weather patterns made tidal surges more likely. Sou’westerlies dominated the weather patterns of the region, but strong northerlies were becoming more prevalent, possibly as part of a 200-year cycle. For all these reasons the east coast, and London particularly, faced an increasing threat from the North Sea.</p>
<h2>Natural climate change?</h2>
<p>Thanks to Waverley, this thinking held sway in Whitehall in the decades that followed, shaping the tortuous process that led to the construction of the Thames Barrier. But if climate change was understood to be a factor in the growing threat to the east coast, there was little suggestion that any of it was caused by human activities. Instead, scientists pointed to the shift in and out of ice ages that occurs naturally over many thousands of years. Climate change, considered a force of nature, had yet to be politicised, even as it became a factor in policy making.</p>
<p>The threat climate change poses a given population depends as much on the capacity of the state to build adequate defences as it does on geographical good fortune. The debate of the 1950s and 60s also throws into sharp relief how politically significant anthropogenic notions of climate change have become. </p>
<p>Then, it was a question of defending vulnerable people and infrastructure against apparently natural phenomena, now the question of causation has hugely complicated and politicised possible government responses. This raises profound questions about environmental justice at both a national and global level. As the terrible flood of 1953 and recent events throughout the world have shown, it is poor, marginal people who drown in floods, whether in Britain or elsewhere.</p><img src="https://counter.theconversation.com/content/71310/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Matthew Kelly does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Scientists correctly realised there was an increasing risk of major flooding. But they didn’t know humans were to blame.Matthew Kelly, Professor of Modern History, Northumbria University, NewcastleLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/237012014-02-26T14:31:25Z2014-02-26T14:31:25ZWill it be ‘all change’ on the railways after Dawlish? More likely just the usual service<p>With the <a href="https://theconversation.com/invest-in-railway-lines-like-one-at-dawlish-before-they-wash-away-22919">collapse of the line at Dawlish</a> in Devon cutting off railway services to Plymouth and the southwest for months, Secretary of State for Transport Patrick McLoughlin MP and Network Rail chiefs were brought before the <a href="http://www.parliamentlive.tv/Main/Player.aspx?meetingId=14953&player=windowsmedia">Transport Select Committee</a> to answer questions about the implications.</p>
<p>In terms of future investment, while losing a railway line or road undoubtedly inconveniences some, the two questions to answer are over the economic impact of such a loss, and how often losses of such severity are expected.</p>
<p>Within hours of the news, calculations adorned the backs of hundreds of envelopes, producing seven, eight or even nine-figure sums of <a href="http://www.bbc.co.uk/news/uk-england-26062712">economic turmoil</a>. Any transport economist would first calculate the cost to the system’s users, following a well established tradition which shows that users value loss of their time during a disruption at around three times the rate that they value time saved on a journey. Typically these are for disruptions over the course of a day, not over a month or more as will be the case due to repairs at Dawlish. There are also well understood penalties for travellers that have to change between modes of transport – the dreaded replacement bus services do not score highly.</p>
<p>So these costs can and will be quantified. As a rough measure, Plymouth station serves around 2.6m passengers per year and Penzance another half a million, so the costs generated by these comparatively quite modest passenger numbers (London Underground carries <a href="http://www.tfl.gov.uk/corporate/modesoftransport/londonunderground/1608.aspx">3.36m passengers a day</a>) won’t take us close to vast sums bandied about by the back-of-the-envelope economists.</p>
<h2>Figures to lay foundations on</h2>
<p>The really big figures are derived from the effects on the wider economy, as put forward by the <a href="https://www.gov.uk/government/policies/supporting-economic-growth-through-local-enterprise-partnerships-and-enterprise-zones/supporting-pages/local-enterprise-partnerships">Local Enterprise Partnerships</a>, town and county councils from the southwest appearing before the select committee. They provided figures that claimed losses to tourism, trade, and potential investment of £4m-£5m a day to the Plymouth economy and £8m to Cornish tourism. </p>
<p>Can it seriously be argued that losing a train service alone has led to a 75% drop in tourist bookings? Clearly any research based on self-reporting by the local chambers of commerce is limited, and the impression given at the hearing by the councillors and executives was that the collapse at Dawlish was also an opportunity to argue for a reversal of historic underinvestment in the region.</p>
<p>So while there will certainly be economic losses, we don’t know what or how much, nor how to disentangle the short term effects such as tourism bookings from the long term effects, for example of major businesses not locating to the region. To me, the figures thrown about are not credible, but to quibble is to miss the point: the effects of major transport disruptions on the wider economy are not well understood, and are not properly accounted for in the decisions that underpin infrastructure investment. </p>
<p>The implication is that those areas that are particularly vulnerable to severe damage and disruption from events like Dawlish will have been short-changed in terms of past investment.</p>
<h2>Doing nothing may be the right thing</h2>
<p>The second question is how often this scale of service outage is likely to occur. Network Rail and the Met Office <a href="http://www.bbc.co.uk/news/uk-england-devon-26335125">have concluded</a> that the combination of high winds, high seas and rain had led to a scale of damage not seen before – but the past is not necessarily a good guide to the future. While it was good news for the representatives of the southwest that it had opened up discussion around proposals for alternative bypass routes, or additional breakwaters around the Dawlish stretch of the line, that was as far as the good news went.</p>
<p>Network Rail’s chief executive reeled off tales of weather-related woe: flooding at 250 sites across the network, and more than 50 landslips in Kent alone (compared to the usual three) at an estimated cost of £170m. Such extreme weather has led to calls for investment from areas besides just the southwest, and while £170m is a significant spend, the demand for investing in network resilience will surely force some re-evaluation of priorities.</p>
<p>The problem is that we don’t know how often these types of events will happen – and that information is a major factor in whether to carry on with business as usual, or to call “all change”, and launch a much greater programme of investment in resilience measures throughout the network. New investments are assessed over a 60-year period: if we think another Dawlish-level-event will remain a rare, it makes little sense to spend heavily on preparing for it – however inconvenient it may be if, or when, such a severe event happens again. And if we should adopt some kind of precautionary principle, the question is what it would look like, and how much would we (the passenger or the taxpayer) be prepared to pay?</p>
<p>When the water recedes and attention moves on elsewhere, I believe that in the absence of any clear evidence the purse strings will close and it will be business as usual. History is full of examples of major events that fail to bring significant change to policy, despite initial interest – security incidents on US domestic flights before 9/11 are a prime example, and the largely unfulfilled calls for institutional change in the UK after the MP’s expenses scandal another. This is a phenomenon Jones and Baumgartner call <a href="http://press.uchicago.edu/ucp/books/book/chicago/P/bo3644482.html">the Politics of Attention</a>.</p>
<p>The UK’s limited infrastructure spending is allocated on the basis of what benefits the user, primarily time savings on journeys that affect thousands of passengers every day. The recent <a href="http://www.which.co.uk/news/2014/02/merseyrail-tops-which-train-satisfaction-survey-354635">passenger satisfaction surveys</a> suggest that many louder voices will reassert themselves, each with arguments for different investment priorities. But it’s difficult to see an under-used emergency rail bypass around Dawlish making much headway against demands to tackle overcrowding on trains servicing London and the southeast.</p>
<p>I hope to be wrong in some of what I have written above. I believe that the UK does not invest enough in its existing infrastructure, instead focusing on the promise of what economic growth new infrastructure might bring. In the absence of better evidence or perhaps a sudden lurch towards a more risk-averse attitude towards resilience, Dawlish will most likely be consigned to history as a particularly memorable storm in a tea cup.</p><img src="https://counter.theconversation.com/content/23701/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Greg Marsden receives funding from the EPSRC (Disruption: the raw material for low carbon change project, funded under the RCUK Energy Programme, ESPRC Award No EP/J00460X/1)</span></em></p>With the collapse of the line at Dawlish in Devon cutting off railway services to Plymouth and the southwest for months, Secretary of State for Transport Patrick McLoughlin MP and Network Rail chiefs were…Greg Marsden, Professor of Transport Governance, University of LeedsLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/229192014-02-06T14:51:10Z2014-02-06T14:51:10ZInvest in railway lines like one at Dawlish before they wash away<figure><img src="https://images.theconversation.com/files/40918/original/gpfjkzxt-1391696966.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Some of our railways are missing.</span> <span class="attribution"><span class="source">Ben Birchall/PA</span></span></figcaption></figure><p>The assault on British coastlines by storm, flood and sea this winter is a taste of things to come. Rising sea levels and a greater risk of coastal flooding are a significant future threat. Britain is an island nation, and a great deal of important and expensive infrastructure, from ports and harbours to power stations and industry, lies along the coast. Roads and railway links are also vital – some entire coastal regions’ economies depend on key highways or rail links.</p>
<p>The coastal section of the London-Penzance railway line that runs between Dawlish and Teignmouth in Devon is a perfect example. As the main railway connection for the southwest of England to the rest of Great Britain, it is a vital transport link for the Devon and Cornwall economy. Several sections of the line have just been washed into the English Channel by storms, leaving the tracks hanging suspended in space over the waves. Network Rail’s first repair estimates are 4-6 weeks work, with engineers calling it the “<a href="http://www.bbc.co.uk/news/uk-26044283">worst damage they’ve seen in their careers</a>”.</p>
<p>Lying so close to sea level, just a few metres above the waves, the line has been susceptible to frequent closure during high seas and storms ever since it <a href="http://www.southwestcoastpath.com/walksdb/printable-walk/602/">opened in 1846</a>. The past 30 years have seen the problem worsen, coinciding with rising sea levels, but the current damage is the most severe in its entire 178 years of service. It is currently estimated that sea-level will by 2020 have risen <a href="http://www.sciencedirect.com/science/article/pii/S0921818111000920">between 5-7cm from 2010 levels</a>, which by my estimates could double the amount of disruption on the line. By 2050 services could be affected for <a href="http://pearl.plymouth.ac.uk/handle/10026.1/912">several months of each year</a>.</p>
<p>It is not a case of if but when the railway will be lost completely to the sea. It is vital that the region prepares for this eventuality, and although Dawlish is arguably the most iconic coastal railway, there are others in <a href="http://www.bbc.co.uk/news/uk-wales-north-west-wales-25794295">North Wales</a>, northwest England and in Scotland that will face similar problems in years to come.</p>
<h2>Rising tides</h2>
<p>Coastal flooding is most likely when strong storms and low atmospheric pressure combine to drive storm surges towards the coast. Coupled with high tides the effects can be devastating, as shown by the destruction in East Anglia and the Netherlands during the record <a href="http://news.bbc.co.uk/onthisday/hi/dates/stories/february/1/newsid_3749000/3749771.stm">storm of 1953</a>, when tide levels rose to two metres above the predicted high.</p>
<p>So with sea levels set to rise over the next century, these extreme events could become more frequent. Hard-engineered sea defences such as sea walls, rock armour, and breakwaters have been built to protect coastal communities and the services upon which they depend. Around 1,200km of coastline is protected, around a third of the total coastline of England and Wales. This is particularly evident in southern England.</p>
<p>Defence structures are built to a design standard based on the statistical chance of extreme water levels (such as one in 100 years). But it’s estimated that even small changes in sea level can produce a significant upwards trend to those chances. Other factors such as storminess and frequency of surges, and wave characteristics (known as wave climate) that cause coastal flooding are difficult to predict. Yet even with no changes in these factors the coastal threat, like the sea, is rising.</p>
<h2>Living with change</h2>
<p>And as tides rise, budgets shrink. Large cuts to national flood defences have been made and are expected to continue, raising serious fears for the funding of planned flood defence improvements along the coast. In the Southwest, plans to re-route the line have been dismissed as too costly. Taken from a purely transport economics or engineering perspective this may well be correct, but this evaluation does not take into account the wider socio-economic benefits of transport connectivity, such as access to employment, productivity gains, increased business opportunities and improved quality of life. </p>
<p>There is an urgent need to improve how the wider socio-economic benefits of transport can be translated into language that beancounters understand. Without investment, the future of Britain’s transport infrastructure services are at risk of failure and collapse, just as surely as the Dawlish-Teignmouth stretch of railway. The cost of clawing back from that eventuality will far outweigh the admittedly high costs of early intervention and adaptation. </p>
<p>While agenda-setting national plans like <a href="https://theconversation.com/hard-evidence-is-it-possible-to-forecast-hs2s-benefits-20164">HS2</a> and Crossrail steal the limelight, the regional and local lines where infrastructure and services are dense, highly interlinked, and heavily relied upon (especially in rural areas) are slowly abandoned. We must invest in the regional networks to tackle the problems specific to them, such as the Southwest Mainline, as by doing so will improve the resilience of Britain’s transport infrastructure overall.</p><img src="https://counter.theconversation.com/content/22919/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>David Dawson receives funding from the EPSRC and ESRC.</span></em></p>The assault on British coastlines by storm, flood and sea this winter is a taste of things to come. Rising sea levels and a greater risk of coastal flooding are a significant future threat. Britain is…David Dawson, Research Fellow, University of LeedsLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/221362014-01-31T22:03:44Z2014-01-31T22:03:44ZAre storm surges getting worse?<figure><img src="https://images.theconversation.com/files/40120/original/5h86sfpb-1390998593.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The east coast of England in 1953.</span> <span class="attribution"><span class="source">PA</span></span></figcaption></figure><p>Brigid, another Atlantic storm, has hit Britain with heavy rain and gale-force winds, especially the already sodden west coast. The last few months have seen very wild weather, including 100mph winds during October’s St Jude’s storm, heavy rain and flooding, and one of the highest ever storm surges off the east coast.</p>
<p>During these storm surges, large increases in sea level can last from a few hours to several days and span hundreds of square kilometres. Low atmospheric pressure allows the sea level to rise and, with the combination of gale force winds and the Earth’s rotation, water is forced towards the coastline. </p>
<p>The same physics apply whether they are caused by European weather systems (known as extra-tropical cyclones) or those in the tropics (hurricanes). Sea levels during a storm surge can rise by up to 8m in tropical areas, and by more than 3m in the North Sea. A combination of high tide, storm surge, wind and wave conditions can overtop or breach coastal defences, and it is often the storm surge that provides the additional power that drives waves to destructive levels.</p>
<p>Worldwide, storm surges cause significant damage and loss of life. For example, in 1970 a devastating surge during the <a href="http://www.weather.com/news/weather-hurricanes/deadliest-cyclone-history-bangladesh-20130605">Bhola cyclone</a> killed perhaps 300,000 people in Bangladesh, and in more recent years <a href="http://www.metoffice.gov.uk/education/teens/case-studies/katrina">Hurricane Katrina</a> and <a href="http://www.theguardian.com/commentisfree/2013/oct/30/hurricane-sandy-one-year-on-stories-readers">Superstorm Sandy</a> in the US have demonstrated their power.</p>
<h2>Coastal flooding</h2>
<p>Coastal flooding around the UK can be life-threatening in addition to wreaking economic and environmental destruction. The worst in modern times was the <a href="http://www.metoffice.gov.uk/news/in-depth/1953-east-coast-flood">North Sea floods</a> of 1953. Huge waves breached flood defences, and coastal towns in Lincolnshire, Norfolk, Suffolk, Essex and Kent were devastated as seawater rushed into the streets. In the Netherlands 1,800 people were killed while in England and Scotland the toll was 326, and <a href="http://rsta.royalsocietypublishing.org/content/363/1831/1263.full">over 600km<sup>2</sup> were flooded</a>.</p>
<p>An inquiry found that along the 1,600 km of coast affected there were 1,200 breaches, at an estimated cost of £40-£50m – around £1 billion at today’s prices. Today, assets worth £150 billion and 4m people are at risk from coastal flooding in Britain. Analysis by the Environment Agency shows that some <a href="http://publications.environment-agency.gov.uk/pdf/GEHO0609BQDS-E-E.pdf">500,000 homes are at risk</a> of flooding in the Thames floodplain.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/40311/original/rqs5chb4-1391185178.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/40311/original/rqs5chb4-1391185178.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=392&fit=crop&dpr=1 600w, https://images.theconversation.com/files/40311/original/rqs5chb4-1391185178.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=392&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/40311/original/rqs5chb4-1391185178.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=392&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/40311/original/rqs5chb4-1391185178.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=492&fit=crop&dpr=1 754w, https://images.theconversation.com/files/40311/original/rqs5chb4-1391185178.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=492&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/40311/original/rqs5chb4-1391185178.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=492&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Towns underwater in the Netherlands.</span>
<span class="attribution"><span class="source">PA</span></span>
</figcaption>
</figure>
<h2>Battered island</h2>
<p>The sequence of storms that battered Britain in December and January were some of the most severe we’ve seen in recent years. During the 5th and 6th December, measured sea levels in parts of the North Sea were the highest since the 1953 floods, and the Thames Barrier and Dutch flood barriers were closed for several tides.</p>
<p>The largest storm surges struck the northeast coast of England, from Tyneside to Norfolk. Around 400 homes were flooded near Hull, and about <a href="http://www.bbc.co.uk/news/world-europe-25243460">10,000 homes were evacuated</a> in Norfolk and Suffolk. The fact the damage was so limited compared to the tragedy of 1953 is thanks to significant government investments in coastal defences, flood forecasting and sea level monitoring. The UK now has a sophisticated network of <a href="http://www.ntslf.org/data/uk-network-real-time">42 coastal tide gauges</a> for flood forecasting.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/40312/original/2888zf2v-1391185887.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/40312/original/2888zf2v-1391185887.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/40312/original/2888zf2v-1391185887.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/40312/original/2888zf2v-1391185887.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/40312/original/2888zf2v-1391185887.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=473&fit=crop&dpr=1 754w, https://images.theconversation.com/files/40312/original/2888zf2v-1391185887.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=473&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/40312/original/2888zf2v-1391185887.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=473&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Windy and wet and red all over.</span>
<span class="attribution"><span class="source">MetOffice</span></span>
</figcaption>
</figure>
<p>Unfortunately there is little data from 1953 which makes a direct comparison difficult. Water levels at North Shields in December 2013 were 4m, 0.5m higher than in 1953, and the 2013 levels at the Hull Barrier were at 5.8m - the highest ever recorded there. Conversely, water levels in 2013 at Harwich and Sheerness in the Thames estuary were 4.1m, about 0.5m lower than in 1953.</p>
<p>While a detailed scientific analysis of the event will take place over the coming months, the emerging picture is of a storm surge very similar to that of 1953 but which struck with greater force in the north of England, which is explained by the 2013 storm’s more northerly trajectory. Those who study Britain’s never-dull weather know that no two storms are identical, which is why complex statistical methods have been devised to gauge water levels around the coast.</p>
<h2>Staying ahead of the deluge</h2>
<p>The coastal flood warning system, UK Coastal Monitoring and Forecasting (UKCMF), is a <a href="http://www.environment-agency.gov.uk/research/policy/116129.aspx">partnership of agencies</a> monitoring wind, wave, tides and weather conditions. It combines computer models of storm surges and waves with real-time monitoring of coastal sea levels, all interpreted by a team of expert forecasters working around the clock.</p>
<p>The numerical models are subject to continuous improvement as more powerful computers and new scientific insight becomes available. The whole system depends on accurate weather prediction, and it is because of better forecasting that it was possible to provide warnings for the December 2013 storm days in advance. The system also makes use of a technique called <a href="http://www.metoffice.gov.uk/research/areas/data-assimilation-and-ensembles/ensemble-forecasting">ensemble forecasting</a> to quantify the inherent uncertainty in short-term weather prediction. The weather model is run several times, adjusting conditions and parameters to provide a range of outcomes that can then be used to judge the reliability of the forecast.</p>
<p>Any increase in the frequency or severity of flooding would have a serious impact on the economy, society and ecosystems. In global studies based on tide gauge data, trends in extreme sea level have been shown to be controlled by changes to mean sea level rather than changes in storminess. For the UK there is <a href="http://www.mccip.org.uk/media/18620/2013arc_backingpapers_4_slr.pdf">no observational evidence</a> of long-term trends in storm surges. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/40308/original/7y2cb4z3-1391180938.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/40308/original/7y2cb4z3-1391180938.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=334&fit=crop&dpr=1 600w, https://images.theconversation.com/files/40308/original/7y2cb4z3-1391180938.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=334&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/40308/original/7y2cb4z3-1391180938.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=334&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/40308/original/7y2cb4z3-1391180938.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=420&fit=crop&dpr=1 754w, https://images.theconversation.com/files/40308/original/7y2cb4z3-1391180938.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=420&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/40308/original/7y2cb4z3-1391180938.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=420&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Gloom and misery everywhere, stormy weather.</span>
<span class="attribution"><span class="source">John Giles/PA</span></span>
</figcaption>
</figure>
<p>For the time being we should assume that changes to flood water levels will be governed by a rise in the mean sea level. And while the jury is out on changes to mid-latitude storminess in the future, the Intergovernmental Panel on Climate Change is unequivocal in its assessment of <a href="http://www.ipcc.ch/report/ar5/wg1/">the gradual rise in mean sea level</a>: the projected rise in globally averaged sea level for the year 2100 is in the range 0.29-0.82m, depending on greenhouse gas emissions.</p>
<p>Even if there is no change to the storm climate of northern Europe, this rise in sea level is bound to increase the frequency of high water levels, and so the chances of flooding. Investment in weather prediction, flood warning mechanisms and coastal defences must not be neglected.</p><img src="https://counter.theconversation.com/content/22136/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kevin Horsburgh receives funding from The Natural Environment Research Council; the Environment Agency</span></em></p>Brigid, another Atlantic storm, has hit Britain with heavy rain and gale-force winds, especially the already sodden west coast. The last few months have seen very wild weather, including 100mph winds during…Kevin Horsburgh, Head of Marine Physics and Ocean Climate, National Oceanography CentreLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/219072014-01-14T13:59:54Z2014-01-14T13:59:54ZHow do you evacuate a university during a storm surge?<figure><img src="https://images.theconversation.com/files/38766/original/9r763w6h-1389294909.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">No you can't go back for your iPad.</span> <span class="attribution"><span class="source">Dave Thompson/PA</span></span></figcaption></figure><p>“Born on a perilous rock” is the title of a classic book by W J Lewis which describes Aberystwyth past and present; last weekend the town fully lived up to this description. To all intents and purposes, 3 January started as a normal mid-winter day in Aberystwyth with a gale howling in off the sea and spectacular waves crashing off the sea front. Most of the university had extended the Christmas vacation to have a few more days’ rest and less that 150 of the 700 plus students who live in our sea front halls had returned to prepare for their exams.</p>
<p>That it was going to be an unusual evening became apparent when John received a call from his mother-in-law, living in sheltered accommodation by the harbour, saying she was being asked to leave because of the storm. At much the same time Rebecca received a call saying Ceredigion County Council workers were trying to deliver leaflets by hand to all student residences, advising their occupants that evacuate the promenade at least one hour before the high tide at 9.11pm.</p>
<p>How does one evacuate numerous buildings in darkness in the teeth of a storm on a midwinter night and transport people to a place of safety? The answer was to intercept the leaflets and set off the fire alarms in each building in turn, advising the assembled residents to prepare a bag of essentials to be ready to be taken to the main campus. Transport was by requisitioning the small fleet of minibuses owned by the student unions and directing the students to a central place, in a street behind the sea front and from there to the Penglais Campus, several hundred feet above sea level, where we opened up our main refectory and fed and watered our evacuees.</p>
<p>By 8.45pm the evacuation was complete. Having taught and researched hazard management for 20 years John had the opportunity to put theory into practice as it was apparent that his research field had come to him. It was clear we had to make a number of decisions.</p>
<p>When could our students return to their halls? This was straightforward, once National Resources Wales issued this advice and when we had checked our buildings we transported our students back to their halls at 1.30am.</p>
<p>Had the risk of spring tide coupled with storm surge diminished? No. The weather forecast predicted a number of storm events coupled with high tides through to the morning of the 7th.</p>
<p>Was travel to Aberystwyth easy? No, the transport infrastructure was breaking down and trains were not reaching Aberystwyth, being stuck in various flooded stretches of the railway.</p>
<p>Could we easily evacuate 1,000 students from the seafront in the middle of the night during a storm? No.</p>
<p>By midnight on the 3rd, having established these points we made two key decisions:</p>
<p>First, discourage all students from travelling to Aberystwyth from their homes until further notice and certainly no earlier than the 8th. This guidance was issued by email and a variety of social media.</p>
<p>Second, postpone all scheduled examinations by one week.</p>
<p>These bought us the space and the capacity to manage the sequence of storm surges and tides we then faced.</p>
<p>On the morning of the 4th it was clear the seafront in Aberystwyth was badly damaged but we had no need to evacuate during the day as the wind speeds had fallen. On the evening of the 4th given the slightly lower wind speed, we announced a partial evacuation of the sea-facing rooms but not of the whole building at high tide.</p>
<p>On the 5th it was clear we were facing exceptionally high spring tides, storm force winds and a significant storm surge. All students were clearly briefed by email, social media and video and were evacuated to Penglais Campus again, where they were very well fed and given a bed for the night.</p>
<p>The clear lesson learned for us was to break the problem down into its constituent parts, establish what our priority was and then make the decisions we needed to make, however large and potentially disruptive they may be.</p>
<p>We are now planning for the next spring tides in late January and early February and in particular the very high 5.8 metre tide scheduled to arrive late at night on 2nd February. Wish us luck.</p><img src="https://counter.theconversation.com/content/21907/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>“Born on a perilous rock” is the title of a classic book by W J Lewis which describes Aberystwyth past and present; last weekend the town fully lived up to this description. To all intents and purposes…John Grattan, Pro-Vice Chancellor, Aberystwyth UniversityRebecca Davies, Pro-Vice Chancellor, Aberystwyth UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/218252014-01-09T13:52:50Z2014-01-09T13:52:50ZSaving coastlines from flooding is an uncertain science<figure><img src="https://images.theconversation.com/files/38742/original/w7qwz5q8-1389267300.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Swings and roundabouts: sea level rises are hard to predict.</span> <span class="attribution"><span class="source"> Danny Lawson/PA</span></span></figcaption></figure><p>Coastal and river flooding struck Britain again this week with huge waves hitting southern and western coasts and around 100 flood warnings still in place by Wednesday evening. Disturbing but, sadly, not unfamiliar scenes were accompanied by an impressive catalogue of disruption and bitter tales of avoidable personal tragedy. </p>
<p>But was this weather or climate? Must we expect more of these kinds of events and if so what can we do about it? As with all things climatic the answers are far from simple, but we can start with three basic facts. </p>
<p>First, a warmer atmosphere can hold more water, so at the simplest level, the global hydrological cycle is likely to intensify. This suggests it’s likely to get wetter somewhere, but not necessarily everywhere. Second, the ocean will expand as it warms, leading to rising average sea levels in the coming decades – this is one of the most confident predictions of climate-change science. Third, any melting of the continental ice sheets on Antarctica and Greenland would raise global sea levels further. </p>
<p>Of these three factors, only more intense storms would affect river flooding. Changes in storms are extremely difficult to predict, and will vary between regions, while river flooding is also affected by highly local factors related to soils and land use. If river flooding is changing already then the signal is not yet clear, but the <a href="http://rsta.royalsocietypublishing.org/content/370/1966/2143">evidence from the past</a> is that relatively modest climate fluctuations since the last glacial period have been accompanied by substantial changes in flooding regimes.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/38748/original/7z442799-1389270736.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/38748/original/7z442799-1389270736.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=387&fit=crop&dpr=1 600w, https://images.theconversation.com/files/38748/original/7z442799-1389270736.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=387&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/38748/original/7z442799-1389270736.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=387&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/38748/original/7z442799-1389270736.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=487&fit=crop&dpr=1 754w, https://images.theconversation.com/files/38748/original/7z442799-1389270736.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=487&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/38748/original/7z442799-1389270736.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=487&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">How much bigger will Blackpool’s waves get?</span>
<span class="attribution"><span class="source">John Giles/PA </span></span>
</figcaption>
</figure>
<p>But coastal flooding is another story. Although individual events are highly dependent on winds and tides, and hence subject to the same uncertainties as inland storm behaviour, the inexorable rise of sea level in response to ocean warming shifts the probability of coastal flooding steadily upwards. </p>
<p>The fact that the dynamics of ice sheets are hard to predict just means we can’t be sure how fast sea levels will rise, but the “likely” range from the <a href="http://www.climatechange2013.org/images/uploads/WGI_AR5_SPM_brochure.pdf">IPCC</a> is 26-82cm by 2100, so the uncertainty is as big as the signal itself. Indeed even predictions of the warming component of sea level rise depend on poorly understood processes such as the rate of transport of warm water to the deep ocean and typically vary by a <a href="http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-12-00584.1">factor of two</a>.</p>
<h2>Protection pays, but how much?</h2>
<p>As rising sea levels will mean more coastal flooding it might seem the answer is clear – invest in sea defences now to avoid damaging floods before they happen. But how much to invest, where and when are much harder questions to answer. We’ve already seen that the rate of sea level rise is highly uncertain, but this is only one factor in the equation of cost versus benefit of sea defences. </p>
<p>Just as important is the value of land to be protected, which depends on how it is used. If land is built on, the degree of coastal development invokes public planning policy as well as private and commercial development decisions. And if land at risk is used for producing marketable agricultural or commercial output, then the value depends on the price of those goods on international markets.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/38745/original/gd82v3gw-1389270155.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/38745/original/gd82v3gw-1389270155.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/38745/original/gd82v3gw-1389270155.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/38745/original/gd82v3gw-1389270155.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/38745/original/gd82v3gw-1389270155.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/38745/original/gd82v3gw-1389270155.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/38745/original/gd82v3gw-1389270155.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">What value the Aberystwyth foreshore?</span>
<span class="attribution"><span class="source">Antony Stone/PA</span></span>
</figcaption>
</figure>
<h2>Science or policy first?</h2>
<p>Any decision of where and how much to invest in coastal protection is thoroughly mired in uncertainty. The rate of sea level rise is highly uncertain, and the statistics of individual flooding events even more so. The value at risk depends on the propensity for coastal versus inland development; and the fact that coastal economies are embedded in a globalised world means macroeconomic forces, including international trade, affect the cost-benefit calculation.</p>
<p>So far, the instinct of scientists and politicians has been to take a “science-first” approach, working forwards from the most complete possible scientific knowledge to the best possible decisions. But the science will never be complete and time is short. Much better, <a href="http://link.springer.com/article/10.1007%2Fs10584-012-0655-6">some have argued</a>, to start from the policy end – prioritising the science that is necessary to choose between the policy options that are actually available, and using <a href="http://onlinelibrary.wiley.com/doi/10.1002/wcc.202/abstract">models as tools</a> to explore the most relevant options. </p>
<p>Science first or policy first, we need better ways to making decisions under conditions of uncertainty. The <a href="http://ermitage.cs.man.ac.uk/">ERMITAGE</a> project has taken important steps in this direction by combining models of climate, economy and agricultural production. Initial results confirm <a href="http://www.climatecost.cc/images/Policy_Brief_ClimateCost_Draft_Final_Summary_vs_4.pdf">earlier conclusions</a>: money put into coastal protection pays for itself handsomely.</p><img src="https://counter.theconversation.com/content/21825/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Neil Edwards acknowledges funding from the EU FP7 programme under grant agreement n° 265170 (ERMITAGE).</span></em></p>Coastal and river flooding struck Britain again this week with huge waves hitting southern and western coasts and around 100 flood warnings still in place by Wednesday evening. Disturbing but, sadly, not…Neil Edwards, Reader in Earth Systems Science, The Open UniversityLicensed as Creative Commons – attribution, no derivatives.