Flood resilient cities · vulnerable to floods. “Flood Resilient Cities” is all about how we...

ICE HKA Annual Seminar 2016

Sustainable and Resilient Coastal Development

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Flood resilient cities

Professor David Balmforth Executive Technical Director, MWH

Past President, ICE

Keywords: cities, flooding, resilience.

ABSTRACT: Unlike the ancient world, present day society seeks to impose its will on nature by building defences and installing artificial drainage to protect itself from floods. Success with this approach is now becoming less certain as the effects of global warming and urbanisation increase both the frequency and severity of floods. And in parallel, growing populations and expanding cities make society more vulnerable to floods.

“Flood Resilient Cities” is all about how we deliver a paradigm shift in the way that we manage flood risk in the future. This paper sets out the key challenges that our cities face, focussing in particular on the effects of climate change, population growth, resource depletion and economic instability. Using the lessons learnt from recent floods, it demonstrates not only why a reliance on flood defences and artificial drainage is no longer tenable, but what the response to that might be. It sets out a strategy for building a future in which society learns to live with floods, building flexible response measures not only into the urban fabric but into the culture of our communities.

Flood resilience recognises that we must accept that flooding will, from time to time, occur – that it will become part of our normal lives. Our ability to forecast and give warnings of floods, to effectively prepare for their occurrence, to manage the fabric of society and its infrastructure so that flood damage is limited, and to recovery fully and speedily after an event will be crucial. As will how we design our cities so we can safely accommodate flooding and how we educate our citizens so they become part of the resilience process. Key messages are illustrated with examples from cities that are already making progress on flood resilience. And some of the more radical concepts that might become part of our future are also presented.

Finally the paper demonstrates that good flood resilience strategies can do more than just tackle floods. They can improve the place we live in, help to manage water scarcity, improve biodiversity, and provide amenity and recreational opportunities.

1 INTRODUCTION

Historically the majority of people in the world lived in rural communities, but in 2007 that changed. Today the rural population of the world has stabilised and will slowly decline. In contrast the world’s cities are growing rapidly as we move to a global population in excess of 8 billion by 2030. These cities are highly vulnerable to flooding. In the developing world much of the population growth will be in the poorest communities least able to cope with floods. In



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the developed world, the risks associated with flooding are greater than those faced from terrorism. Yet the experience of recent floods shows that we are making little progress in tackling flood risk. If the world’s cities are to sustain their unprecedented growth, then building resilience against future floods must be at the heart of their development.

2 WATER AND LIFE

2.1 Water as a Friend

An aerial view of the world’s population will show that the majority of people live along the coast or close to the course of a major river. The reasons for this are obvious. People need access to water to sustain life. They use it for growing crops and, since the industrial revolution, water in large quantities has been used to build and sustain the fabric of society. Water also forms a valuable means of transport, across seas and oceans and along inland rivers. The major towns and cities of the world have grown up close to water. Ports have grown up around river estuaries and in delta regions, and where bridges have been built across river narrows. Water also provides a valuable form of defence which is still retained in many of the major cities of the world today.

Early civilisations understood the natural patterns of water. They understood not just the cyclical form of tides but also the exceptional effects of spring and neap tides. They understood the natural river mechanisms that formed flood plains to accommodate the additional flow resulting from exceptional rain. They harnessed periodic floodwater to irrigate their crops and washland sediments to fertilise their fields. When settlements were built in areas susceptible to periodic flooding, homes were built on stilts or on pontoons (a good example being along the Sab River in Cambodia). For many, living next to water was an important cultural aspect of life, adding much to its quality.

2.2 Water as an Enemy

As cities grew the pressure on land for development became more acute and fixed buildings appeared in flood plains and coastal regions. To protect these from periodic floods, embankments and flood walls were built. Not only did this allow cities to expand onto land that otherwise might not have been thought suitable for development, but it also stimulated land reclamation from estuaries and the sea. Such communities then became vulnerable to occasional flooding as defences collapsed or were overtopped. Water was no longer seen as a friend but as an enemy.

Over the years, defence structures and constructed drainage systems have been the primary, and in many cases, the sole means of managing flood risk in cities throughout the developed world. Similar measures are being promoted in the developing world where limited resources permit. Although engineers understand that such measures cannot protect communities from all floods, the level of protection achieved is such that it reinforces the commonly held view that the flood protection is absolute.

3 LESSONS LEARNT FROM FLOODS

Floods have a major impact on communities, destroying homes and businesses, disrupting infrastructure and devastating crops. Over the last 5 years floods have displaced more than 90 million people world-wide. In 1953 a combination of a high tide and storm surge brought one of the major floods in history to the coastlines of the North Sea in NW Europe. In the late hours of Saturday 31st January sea levels 5.6 meters above mean overtopped defences in Scotland and rapidly trapped people in their homes. Without modern communications those further south in England and across the North Sea in the Netherlands and Belgium were



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unaware of their fate and therefore unprepared. Over 1800 people were drowned on land and a further 230 lost at sea. These floods established modern day thinking in coastal defence throughout Europe and led to substantial investment in engineering projects including the Thames Barrier in the UK and the Dutch Delta Works programme.

More recently, in 2005, Hurricane Katrina flooded almost 80% of the City of New Orleans leading to over 1200 deaths and causing more than $100 billion of damage. A large scale evacuation process was only partially successful and hampered by the impact of the floods on infrastructure services, especially electricity. In some parts of the city, the inability to get cash from ATM machines led to looting of grocery and other stores. In only 8 hours from the start of the flood, much of the normal functioning of society had collapsed. New York fared rather better in 2012 when it was hit by Hurricane Sandy. But despite preparations, recovery was hampered by an unforeseen lack of road vehicle fuel, which made it difficult to get recovery teams to the affected areas. Parts of the subway system were out of action for many months as a result of poor preparation. Many areas were without electricity for long periods and over a 100 homes were destroyed by fire. The New York stock exchange closed for two days. Overall more than 50 people lost their lives and the resultant damage was estimated as in excess of $19 billion.

Widespread river flooding in Australia in 2011 affected more than 200000 people causing A$2.4 billion of damage and a reduction of over A$40 billion in the Australian GDP. 38 people lost their lives. In 2013 the highest levels ever were recorded on the Rivers Elbe and Danube in Europe, causing widespread flooding in Germany and Hungary.

Even where communities are protected from river and coastal flooding, flooding can still occur. In 2007 more than 55000 homes in England were flooded as a result of heavy rain. Coastal and river defences were not overtopped, yet the intensity of the rain was such that it generated local surface water flooding. And closer to home, the 2014 floods in Hong Kong demonstrated the vulnerability of low lying communities to the effects of localised intense rainfall.

Although each flood is unique, there are many common conclusions that can be drawn from recent floods. The first is the “unexpected” nature of flooding. Despite improvements in flood forecasting and modelling, society still remains largely unprepared for major floods. In part this appears to be due to an inability to communicate the consequences of foreseen flooding. Even in communities that have suffered flooding within living memory, terms such as “extreme” and “unprecedented” and “we’ve never seen anything like this before” are frequently heard. This is particularly true in areas where residents believe that they are protected by flood defences or storm drainage. Such an inability to foresee the consequences of flooding extends to other stakeholders such as business, utility companies and government departments. The inability to imagine “what if?” results in a lack of preparedness, and in highly developed communities a cascading failure of infrastructure and other services.

The second lesson (unsurprisingly) is that flood water flows downhill and accumulates in low spots. Flood water tends to follow natural flood pathways in flood events, even though they may have been obliterated by dense urban development. The path that floodwater takes is often influenced by small detail in the urban topography and is largely unmanaged. This means that the impact of flooding is random. Surface water can often be trapped behind flood defence walls and embankments and can be a significant risk in areas otherwise well defended against floods.

Finally we realise that we have built communities that are amazingly vulnerable to flooding. From the fabric that we use to construct our buildings to our transport and infrastructure systems and our food and water supply chains. Even a modest amount of flooding can cause electricity and water supplies to be disrupted and transport to grind to a halt. Such is our vulnerability to flood water that it takes many months, and in some cases years, to recover from a flood.



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Of course, many flood experts understand these issues. Yet we fail to engage with society in an effective manner. Perhaps we believe that the knowledge we have will be politically unacceptable to society. Yet those who specialise in disaster management know that the only effective way forward is to be “brutally honest” with those we are responsible for (Dykstra 2010).

4 FUTURE CHALLENGES

Dealing with the present day risk of flooding is challenging. Yet the world is not standing still. We now know that the global mega-challenges will have a significant effect on future flood risk posing an addition and significant challenge. These include:

• Population growth • Climate change • Resource depletion • Instabilities in the global economy From a risk management perspective, climate change will increase the frequency and

severity of floods due to its impact on rainfall intensity and sea levels (Welford 2008). A UK Government study evaluated the increase in flood damage due to climate change impacts by 2080 (Ashley et al 2005, and figure 1). This showed that for the likely global future economic scenarios (World Markets/National enterprise), traditional approaches to flood risk management would become unaffordable, socially unacceptable (due to their disruptive nature) and have a large impact on the environment.

Figure 1 Impact of Climate change on Flooding and Coastal Erosion in England and Wales, assuming the flood

management approach remains unchanged between present day and 2080 (Foresight, 2004)

Population growth will increase the vulnerability of society to floods and also increase the

intensity and frequency of floods due to its effects on the run-off process. This will be especially true in the rapidly growing cities in the developing world. Moreover, much of the future population growth is likely to be in poorer communities less able to withstand the effects of flooding. The makes the impact doubly concerning. Economic instability and depleting resources will make it more difficult for society to respond.

It follows, therefore, that traditional approaches to flood risk management are unsustainable. We need a new paradigm for flood risk management, especially in the growing cities in the world.



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5 THE PARADIGM SHIFT: DEFENCE TO RESILIENCE

The paradigm shift from defence to resilience recognises that we cannot hope to protect all communities from flooding for every conceivable event. Rising sea levels makes coastal communities more susceptible to the effects of spring tides and storm surge. Communities along estuaries and main rivers will also face increasing risk as river levels rise and cities expand into areas naturally used as flood plain. Investment in flood defences and drainage works will continue to be important, both for providing new facilities and also for maintaining existing ones. This will ensure that our towns and cities are appropriately protected from frequent flooding. But alongside this we also need to plan for the occasions when the capacity of these facilities are exceeded. Building resilience in communities and designing for exceedance are not new ideas. As demonstrated earlier, they were well understood by early civilisations. But modern society, both in the developed and developing world, has failed to learn from history.

Resilience is about recognising that flooding will occur, understanding what the consequences of that might be, mitigating the impacts, warning and preparing, responding to events, and then recovering. All these stages are important. They involve structural measures (what we do to the fabric of society and the infrastructure that supports it) and non-structural (the actions we take, before, during and after a flood event). Mapping out the journey to resilience is important, and as with most journeys the first step is often the most difficult.

5.1 The first step: flooding is intentional

This is all about being honest with a community about there being a limit to the degree of protection that flood defences and drainage works deliver. This may simply be a financial constraint, and many communities will suspect this to be the main reason in any case. A useful starting point is understanding that however great the investment there will always be some residual risk of flooding. But there will often be other good reasons why providing more drainage capacity or higher flood defences will not be the best way forward. Flood defence walls and embankments can be a great visual intrusion in a community cutting off natural vistas and communication routes. And large storm drainage channels that remain dry for long periods can attract dumping and other unsocial activities. Good community engagement and sensitive communication will be important to making progress in this first step.

5.2 Understanding the Consequences of Flooding

It is vital that the residual risk of flooding is properly identified and quantified. Modern modelling tools are capable of accurately replicating flooding in two dimensions in real time. When combined with spatial data on impact and vulnerability they can provide a useful visualisation of flood risk for engaging business, utility companies and the public. However such tools are only as good as the data they use. Verification of flood models using data from real flood events is important. Extrapolating the output from models that have been calibrated on lesser events may produce unrepresentative results.

A good model should be able to capture the imagination of stakeholders in answering the question “what if?” By tracing the build-up of flood waters in the community we can identify what will be affected and when. At what point will the local electricity distribution centre be disabled and what then will be the consequences of that? Will this mean that fuel supplies to the city are cut off because the pumps rely on an electricity supply (as was the case in New York with Hurricane Sandy)? Will traffic come to a standstill because the traffic lights no longer work?

Data on velocities and depth will determine which areas will become no-go areas for vehicles and pedestrians. Understanding where the vulnerable are located will help in establishing robust evacuation strategies.



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Good flood modelling will also help to determine the structural measures that might be used to mitigate the effects of flooding. But experience shows that whilst representing flood predictions in 2D drawings or animations might be fine for engineers and other specialists, it lacks the drama necessary to capture the imagination of the public and other stakeholders. Being able to translate flood models into 3D animated images using computer games software may provide a better means of demonstrating the real impact of future floods.

5.3 Mitigating the Impacts

5.3.1 Making space for flood water Flood water passes through city landscapes following the line of greatest slope and fills up low spots along its path. It uses roads and pathways as channels, and depths build up where buildings obstruct its path. In extreme cases whole buildings can be washed away in its path. The direction of flood pathways is often influenced by relatively small details such as kerb heights or local depressions. This passage of floodwater is unmanaged, but this does not have to be the case (Balmforth et al 2006).

The impact of flood water in cities can be significantly reduced if space is created for flood water to pass. Because land in most cities is at a premium we tend to build over watercourses and up to the banks of rivers. We remove the space naturally used to convey flood waters. Equally on the coast, we build right up to the water line (or beyond when reclaiming land), leaving little space for the natural land that can dissipate the energy of large waves. A key element of mitigating the impacts of floods is therefore to create the space for flooding to occur.

Good city design incorporates the space for floodwaters from the start (Barker and Coutts 2016). However creating this space in existing city landscapes is difficult. Many city planners understand the need to pull back development from the fringes of rivers and from the coastline yet they are under pressure from developers who want to redevelop the land and from city governors who want to maximise the commercial earnings from land.

A good example of making space for flood water is the Dutch programme “Making Room for the River” (Reimerink 2015). Nijmegen, a city of 170000 people on the River Waal in the Netherlands suffers from flooding due to the narrowing of the river channel on a sharp bend. The proposal is to create an additional flood channel within the urban area so that excess flow can pass safely through the community. This will involve moving 50 homes and two business to create the space which will be used for recreational purposes when not in use for flood management (figure 2).

“Managed retreat” therefore becomes an important tool in the process of mitigating the effects of flooding. It applies equally to river and coastal flooding. Indeed, managed realignment of coastal regions has now become normal practice throughout North West Europe (Legget et al 2004). As a principle it is less well established within city areas however.

Figure 2 Managed Retreat in Nijmegen as part of the Dutch Making Room for the River Programme

http://citiscope.org/authors/letty-reimerink



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5.3.2 Creating flood pathways and sacrificial storage Once space for floodwater has been created, surface flood pathways can be created to direct flood water away from vulnerable parts of the community to areas designated for temporary flood storage. Known as “sacrificial” flood storage areas, these can be areas that at other times have a different function in the urban community. Examples of such dual use areas might be municipal parkland, car parks and urban squares (figure 3). The Dutch have devised the name “Water Squares”.

There has been obvious resistance to such measures. Engineers may be reluctant to deviate from well used design standards in order to facilitate this dual function. City governors worry about safety aspects and impact on the local economy. Strong leadership is therefore needed to drive through such innovative measures and this is one of the reasons why, internationally, progress in this area has been rather slow. Yet it offers important benefits for the future.

Figure 3 City Square in Brazil that creates Sacrificial Storage during Flood Events

5.3.3 Making buildings and infrastructure resistant to flooding Conventional buildings are particularly vulnerable to flood water. Buildings with low thresholds can allow flood water to enter even where flooding externally is not extensive. Flooding of the order of only 300mm can cause extensive damage. The threshold level of a building is the principal factor in making it more resistant to flooding. Raising buildings onto stilts or land platforms that set it above the level of the surrounding ground is the main means of achieving this in new development (figure 4). For existing buildings flood proof doors and shutters can be retrofitted (figure 5). These can be manually operated or automated (triggered by rising flood water). Alternatively local flood defence walls or embankments can be used where land permits, but these can often be unsightly.

Similar measures can be used for infrastructure, and this can go a long way towards avoiding the cascading failures described in section 3. The current design of metro stations in Singapore requires a platform at least 1m above the surrounding ground (figure 6) which has resulted in the metro remaining in effective operation during all the recent floods.

5.3.4 Making buildings resilient to flooding We can only resist flood water entering a building up to a certain point. A large differential head of water between the inside and outside can cause structural failure. Thus we can expect flood resistance measures to be overtopped on occasions. Traditional building materials are easily damaged by flood water and buildings become waterlogged so that they take many months to dry out.



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Figure 4 Raised Threshold on New Shopping Mall, Singapore

Figure 5 Mechanical Flood Barrier, Sheffield, UK (courtesy Tilt Dam Ltd)

Figure 6 Raised Threshold on Metro Station, Singapore

The use of cementitious materials, concrete floors and high level electrics, together with

lightweight furniture and furnishings that can readily be moved, means that flooded buildings



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can be back in use in a matter of hours after a flood. Once people have experienced the benefits of such methods they are much more likely to accept resilience measures as a robust way of managing flood risk.

5.3.5 Flood smart buildings and infrastructure Buildings that respond to varying water levels have progressed beyond the prototype stage and are now being implemented in the Netherlands. Whole streets have been built successfully and there are plans to develop floating cities. The success of living with water in such a way is amply demonstrated by the ancient city of Venice (though of course the ancient buildings did not float) but it does not fit the culture of all societies. Nevertheless it is a serious development and could be a useful means of tackling sea level rise in many of our coastal communities in the future.

One drawback of floating buildings is their tendency to move with the movement of the water. This is not to everyone’s taste. To overcome this buildings can be restrained or tethered. Figure 7 shows a house recently built on the banks of the Thames near London. The house is constructed on a buoyancy tank held on vertical guide rails. As the river level rises so does the house. A series of terraces allow easy access at different levels and flexible service connections provide the usual facilities.

Figure 7 Buoyant House on the River Thames, London (Courtesy Baca Architects)

5.4 Warning and Preparing

Our ability to forecast storm events has improved dramatically in recent years. Hurricane Sandy was accurately predicted in 2012 so the citizens of New York had time to prepare. Conditions leading to large catchment river flooding can also be predicted though this is easier in areas subjected to frontal rainfall. In NW Europe an accurate forecast of rainfall intensity and location is now possible four days in advance from global instrumentation and C Band radar stations. In areas subjected to monsoon rainfall and high intensity convective rain, forecasting is less reliable, though the advent of X Band radar now offers opportunities to better understand the rapid formation of rain cells and give better advanced warning of extreme rain events and coastal storm surges. Making local radar rainfall data available in real time via the internet is an important step forward in communication. The ability to access such data from smart phones and receive automatic warnings is proving a success in helping people to prepare.

Forecasting is not the same as warning. An effective warning of forthcoming floods relies on two important factors. The first is our ability to turn the forecasted weather data into an estimate of flood impact. Again both modelling and experience of recent floods can help with this process. The second is to communicate the likely forthcoming event in a meaningful way



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to stakeholders and the public. Experience suggests that those responsible for action in the event of a warning tend to err on the side of either disbelief or underestimating impacts. There appears to be a concern that if they take action but the flood does not arise (or is not as severe) then they will be held accountable. Their view is reinforced by false forecasts, an inevitable part of a system that is intrinsically uncertain. The same view is often held by the public, with the added problem that they often distrust messages from government or private organisations. Forming local flood resilience groups and engaging people through social media can help overcome these issues.

Preparing for forecasted events can range from simple actions individuals can take (moving family heirlooms or important company documents upstairs) to sophisticated corporate response (temporary office accommodation, community rescue shelters, assembly of portable pumping equipment). It is also important to understand that with good forecasting and preparedness, much can be done to protect communities through the use of temporary flood defences. These can range from whole flood walls (figure 8) to localised measures that protect individual property or infrastructure (figure 9).

Figure 8 Temporary Flood Defences (Courtesy Environment Agency, UK)

Figure 9 Property Level Temporary Flood Barrier



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There is a really important lesson here for infrastructure providers, utility companies and the suppliers of essential services. The issue of cascading failure caused by the high connectivity of services in modern cities has been raised in section 3. Why is it that in most major floods one of the first consequences is that the electricity supply fails? Why does so much of our critical infrastructure that relies on electricity not have a back-up supply? How is it that so much of our major services that rely on people to operate it give no thought as to how those people might get to their place of work during a flood? Why do we not build more redundancy into our systems and have more free standing means of operation? These are key questions that we have yet fully to come to terms with.

5.5 Responding to Events

The responsibility for responding to major floods lies with regional/municipal government and central governments. The jurisdiction that needs to be engaged should be one order of magnitude greater than the area affected (Dykstra 2010). Thus a region needs to respond to a municipal flood event, a country to a regional event and multiple nations for a nation-wide event. This scaling up applies in all areas of society from business to health care.

Effective response is a key element to building the resilience of communities. Many different agencies are likely to be involved and agreeing who will be in charge in advance of an event is vital. Successful response is all about good organisation, strong leadership and effective communication. Rehearsing emergency response should be a routine event for all municipalities. This is particularly important if evacuation of the vulnerable is part of the preparation or response.

However, it is said that what distinguishes a disaster from an emergency is that in the former the prepared response systems break down. In such cases the public are often the first responders, being local to the flood. They also need to be engaged therefore in preparing for floods. Indeed their role is central to effective response in all cases. Local people understand who will be vulnerable to floods, where local resources lie and who is good at doing what. Local groups can be enormously resourceful in emergencies which is why they need to be part of the organised response.

5.6 Recovering

Effective recovery is an essential part of building resilience to flooding yet is perhaps the one that is most overlooked after the immediate heroic efforts of responding to a flood. Many businesses and government departments in the developed world have business recovery plans that are supposed to allow the business to survive a major emergency. These are designed to ensure business or service continuity. Valuable though they can be, experience shows that they are only as good as the organisation’s ability to answer the question “what if?” Often they assume that only the particular business or service entity is affected, so for example they might not account for the regional failure of electricity. They may not accommodate the effects of transport disruption. They may not even allow for the fact that their employees cannot get to work.

Some of the best lessons learnt on disaster recovery in modern cities arises from the Christchurch earthquake in 2011. A clear and holistic vision on what the future of Christchurch should be like in the future, engagement of all the relevant organisations through the Canterbury Earthquake Recover Authority (http://cera.govt.nz/) and good organisation has helped the community navigate the many barriers that have to be overcome in such a major recovery programme. Distinguishing between the short-term needs of getting some basic function back into the city, compared with longer term requirements, was an important early step.

Too often individuals are left to their own devices to recover from flooding. Even those well-educated and well insured struggle to manage a complex process at a time of extreme anxiety. In such cases it may mean many months or even years before physical recovery is

http://cera.govt.nz/



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complete, and the psychological effects can be far more long lasting. Those who are less well-off and who may not have insurance face considerable loss and may never recover. In Hull, UK, some families were still living in caravans eighteen months after the 2007 floods. Many businesses that close in a flood never reopen.

6 DELIVERING MULTIPLE BENEFITS

So far the focus has been on how we can manage flood risk in a more holistic and effective manner by making our cities more resilient to floods. The structural and non-structural measures proposed challenge the way we engage with society and the way we plan our urban areas. We can, of course, limit our approach solely to addressing flood risk. But that would be to ignore the many opportunities that a wider vision might deliver. These are, on the one hand, to deliver multiple benefits from flood resilience, and on the other, to place flood resilience at the heart of urban design through welcoming water back into our communities (Barker and Coutts 2016).

There are many benefits that can be realised through addressing flood resilience in an integrated way. These include amenity, biodiversity, urban cooling and water resources. Many cities are now looking at how green corridors can be integrated into the urban landscape to provide better places in which people can live and work. Integrating the water cycle into these ideas (the blue corridor) leads to the concept of blue-green corridors (http://www.bluegreencities.ac.uk/bluegreencities/index.aspx).

These concepts demonstrate how we can make living along the coast or near to a river a virtue rather than a threat. How, by opening up urban river corridors, we can create valuable space for recreation and biodiversity. The Connswater Greenway project in East Belfast (figure 10) created a linear park around an old canalised river. In addition to the amenity benefit it improved the conveyance of flood flows removing the risk of flooding to local housing. Queens University Belfast has shown that the health benefits arising from this scheme will be more than the investment in delivering the scheme (http://connswatergreenway.co.uk/video/queen%E2%80%99s-university%E2%80%99s-public-health-research-on-the-connswater-community-greenway).

In Singapore, the Singapore River is retained behind a marine barrage to create the marina bay lagoon. The facility provides protection from coastal flooding, an important amenity to the downtown area and a resource for regional water supply. Since the storm drainage for the catchment also drains into the marina bay then storm water run-off is captured as a water resource.

Figure 10 Connswater Greenway Project, East Belfast, incorporates a linear park and urban flood control exceedance channel

http://www.bluegreencities.ac.uk/bluegreencities/index.aspx

http://connswatergreenway.co.uk/video/queen%E2%80%99s-university%E2%80%99s-public-health-research-on-the-connswater-community-greenway

http://connswatergreenway.co.uk/video/queen%E2%80%99s-university%E2%80%99s-public-health-research-on-the-connswater-community-greenway



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7 CONCLUSIONS

Flooding is one of the biggest challenges that cities face. It has been shown that traditional approaches of increasing drainage capacity and building bigger flood defences will not be sustainable in the future. A different paradigm for flood risk management is now needed. Although traditional methods will still play an important part, making urban communities more resilient to flooding must be at the heart of our future strategy.

Enabling urban communities to live with floods will not be an easy task. However, many of the measures now needed have already been proven in practice. These include:

Better forecasting and warnings Improved modelling and visualisation of impending floods Making space for flood water so that it can safely pass through communities and be

stored in “sacrificial” flood areas Making buildings and infrastructure more resistant and resilient to flooding Improved engagement of the public, business and other stakeholders so that they

become part of the solution Better preparation for installing temporary measures and for responding to floods Improved recovery and better support for those affected

The 2004 Foresight project (Ashley et al 2005) showed that by adopting such an

integrated portfolio of work, future costs could be contained within manageable levels (figure 11). This work was revalidated as part of the review into the UK floods of 2007 (Pitt 2008).

Figure 11 Impact of Climate change on Flooding and Coastal Erosion in England and Wales, assuming the flood management approach is based on a portfolio of responses (Foresight, 2004)

Moreover, by combining flood resilience strategies with those for greening the

environment of our cities, we can deliver further benefits including improved amenity, bio-diversity, public health and water resources.

Average annual flood damage in 2080s for the four future

scenarios - baseline damages (assuming no change in

policies) compared with damages following implementation

of the integrated portfolios of responses

0

5

10

15

20

25

Present day World Markets National

Enterprise

Local Stewardship Global

Sustainability

baseline ? billion

integrated portfolio ? billion

£bn



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8 REFERENCES

Ashley RM, Balmforth DJ, Saul AJ, and Blanksby JD (2005) Flooding in the future – predicting climate change

risks and responses in urban areas. Journal of Water Science and Technology, 52(5): 265-273.

Barker R and Coutts R (2016) Aquatecture: Buildings and Cities Designed to Live and Work with Water, RIBA,

London

Balmforth D, Digman C, Kellagher R, and Butler D (2006) Designing for Exceedance in Urban Drainage – Good

Practice. Report No. C635, CIRIA, London.

Dykstra EH (2010) The Storm. Uitgeverij Kluwer BV, ISBN 10: 9013062539 ISBN 13: 9789013062533

Foresight Project (2004) Climate Change, Floods and Coastal Defence, Office of Science and Technology,

London

Leggett D J, Cooper N and Harvey R (2004) Coastal and Estuarine Managed Realignment – Design Issues

Report No. C628, CIRIA, London.

Pitt M (2008) Learning the Lessons from the 2007 Floods Cabinet Office, London.

Reimerink L (2015) A Dutch City Makes Room for its River — and a New Identity, Cityscope.org.

http://www.ciria.org/acatalog/C628.html

http://www.ciria.org/acatalog/C628.html

http://citiscope.org/authors/letty-reimerink

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