September 2015
Overview
0 minutes – Introduction
2:00 minutes – Lecture begins
03:45 minutes – The context behind flooding in cities
09:20 minutes – Cities that are leading the action
41:20 minutes – How does London compare with these cities
51:30 minutes – Conclusion
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Teaching ideas
View the Lecture here (11th May 2015):
Why are cities highly vulnerable to flooding and climate change?
Cities are more vulnerable today to the negative effects of extreme flooding and climate change events than at other points in history because as spaces, they almost all hold a much higher concentration of people. In 1950, 746 million people lived in cities: a figure that in 2014 stood at 3.9 billion. By 2030 it is predicted that sixty six percent of the world’s population will be urban dwellers. As well as sheer size making cities more vulnerable, new growth in the cities is increasingly happening on the city margins and in places where residency was not planned into the city design. These marginal dwellers are often at greater risk of flooding; occupying for example flood plains, marshland, coastal lowlands or places that lie outside those already protected by flood defences.
In relation to climate change, human beings do not have a good track record of being able to change their behaviour and adapt to the increases they have seen in extreme weather events. Every year since 2000, the UK has seen such an event happen and in the case of the winter of 2013-14, which was the wettest in the UK for two hundred and fifty years, can cause large scale economic loss and in some cases delay the socio-economic development of cities. During, and as a result of extreme weather events, the price of goods rises disproportionately higher in cities than in other areas and the increased value of insurance claims is also witnessed more acutely there.
Though people may be thought to be more at risk in cities, one should not dismiss urban spaces as places where people cannot also learn to be resilient to extreme weather patterns.
What can cities do to protect themselves from flooding and the effects of climate change?
Though the amount of global rainfall each year has roughly stayed the same throughout the last century, there is a marked difference in when it falls and the intensity of individual rain events, with a move towards more extreme episodes. The average city infrastructural system is not always designed to cope with such deluges, nor with periods of extremely low rainfall, and across the world there have been incidences of system failure and loss of human life as a result.
One city that has reacted to extreme ‘cloud burst’ events is Copenhagen. Between 2005 and 2011, the city experienced many of these events, with one flood in 2011 being caused by twenty centimetres of rain falling in under three hours. The city’s major road networks were taken out of action and the city was so deeply under water in parts that the central hospital could not be evacuated as there was no route out of the district in which it sat. Over €1 billion of insurance claims were made in the city from that one rain event alone.
As a result Copenhagen launched the ‘Copenhagen Climate Adaptation Plan’ which included a ‘Cloud Burst Management Plan’ in 2012. The plans set new standards for managing surface water, precisely detailing how the €1.3 billion worth of new measures were going to be funded and initiated a set of legislative changes that made Denmark arguably the most radical and leading nation in climate change adaptation. The combination of hard and soft engineering solutions, which are due to be built across the city over the next twenty years, will prepare the city for a 1 in 100 year storm by pumping water into areas where water would not naturally flow and be stored. By modelling the way that flood water behaves, city engineers were able to design an almost entirely new city plan. Central to the planning was the idea that climate change adaptation would not be seen as restrictive or a negative concept: though Copenhageners were being asked to pay for the schemes through a ten percent increase in their water bills, the perceived better quality of life that would come with the increased recreational spaces the plans offered opposed this.
The city was divided into seven water catchment areas. Running through almost all of them will be a cloud burst tunnel which will try to keep rainwater out of the drain system and stop it emptying into other parts of the city too quickly. ‘Pocket Park’ will be built: large green spaces with central raised ridges through their centre. In times of flood the grass areas below the ridge will fill with water but the ridge will allow the area to still be navigable on foot. ‘Cloud burst boulevards’ will direct water to drier areas. These canals will be used as cycle paths (and in some cases, roads) during dry weather but will purposefully fill with water during floods. Other roads will house a central convex shaped strip of grass, which will become a river channel during flooding but provide an attractive cityscape between floods.
Planners say the strength of the plans are in the way they are not just about flooding – improved access through the city, greater recreational space, air pollution removal and added value to house prices have all been incorporated to make the plans feasible.
Other adaptation schemes in place in other world cities.
How prepared is London for Flooding and Climate Change?
London is at risk of both extreme heat (and associated droughts) as well as flooding. The city is expected to gain an additional three million people by 2050, with an estimated net 100,000 people moving to the city every year until then. Fifteen percent of the city sits on the Thames’ former flood plain and an estimated seventy three thousand properties are considered to be in a high risk of flooding.
Yet for the amount available, Londoners take more water out of the system than most city dwellers worldwide and there is less usable water per head in the capital than in most Mediterranean countries. Much of the cityscape has been designed to retain warmth and planned with a temperate climate in mind. However at temperatures above 24.7°C, Londoners start to feel the negative effects of the weather: for most commuters this can be seen in a slower running train system as lines buckle and morph in the heat, but reservoirs, that feed the city its water supply, are also frequently having to be restocked with water from further afield.
The Thames Barrier, a tidal flood defence designed to prevent weather and climate induced tidal surges from flooding London is being closed increasingly more often. The gates on the barrier were closed forty one times in the winter of 2014, making up a quarter of the total number of closures since the barrier was first operational in 1982.
Conclusion
London has a lot to learn from cities like Copenhagen. Central to new adaptation planning should be design that prepares for the worst scenarios that could come with any climate change future. Multiple levels of protection and resilience need to be built into the fabric of many of the world’s principle cities, and in such a way that the integrity of aiming for healthy city living is not compromised. Combining hard and soft engineering projects and using both the urban environment and new parkland and greenspace can benefit not only those most at risk of a severe climate event, but also the wellbeing of all city inhabitants in a variety of climate change futures.
References
Unless otherwise stated, all data in the above piece relates to figures taken from Alex’s lecture.
Key Words
Climate Change
A substantial change in the long term weather patterns of a particular place.
Flash Flood
Sudden, rapid and high volume flooding caused by heavy or excessive rainfall or snow melt in a short period of time.
Hard Engineering
Measures taken to prevent the impact of a natural hazard or phenomenon by means of physical structures and changes to the landscape.
Infrastructure
The services and facilities needed for an economy to function, for example transport networks, energy supply and health care.
Pluvial
Connected to or relating to rainfall.
Soft Engineering
Measures taken to prevent the impact of a natural hazard or phenomenon by means of non-physical structures, such as education programmes or designed social changes.
Lesson Ideas
Students can look at their own school grounds (or area using the Environment Agency website) and assess which areas are most likely to flood. In groups they can then design a flood action plan for the school which minimises damage to people and property, integrating hard and soft engineering ideas together.
Researching the Copenhagen Climate Adaptation Plan, students can copy one of the sketches and annotate it to show how the measures work. Annotations can also be made to show how the plans can be a positive step environmentally, economically and socially for the city.
How might the kind of engineering in Copenhagen differ to a city in a developing country? Students can explore how a country’s GDP affects the options open to them in coping with and adapting to climate change.
Links
The Copenhagen Climate Adaptation Plan
60 second guides
Articles
Ask the Experts
Resources
Are you flood ready?