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How resilient are our cities to climate change? Ian Allison

‘If I were you, I wouldn’t be starting from here’ is the punchline to the familiar joke about a tourist asking for directions.

If asked how to build resilience into a city, and I’m not saying this for a laugh, I would be tempted to reply ‘I wouldn’t have built the city here in the first place’, that is, on low-lying land on or near the coast, or on major tidal waters and deltas – where many of the world’s biggest cities are located.

These cities are where they are for historic reasons – they grew on the back of settlements and maritime trade. But climate change combined with increasing urbanisation and land subsidence could lead to more than a nine-fold increase in the risk of flooding in the world’s major port cities between now and 2050, according to a report commissioned by the OECD and published in the journal Nature Climate Change (i).

Climate impacts respect no boundaries with cities as diverse as Mumbai and Miami among the most vulnerable.

Cities will experience climate shocks of greater intensity and frequency as a result of global warming. But we still have time to make them more resilient to climate change, and hence safer – if we take the right action.

Storm Desmond
In early December 2015, just as government ministers from around the world were meeting in Paris to negotiate the COP21 treaty, Storm Desmond hit the northern part of the UK. Carlisle recorded 300mm of rainfall in just 24 hours.

On the same weekend, the southern part of India was hit by an El Nino influenced storm and Chennai was also deluged with 300mm of rainfall in 24 hours.

Carlisle and Chennai suffered similar economic losses of between $1bn and $2bn. But whereas the deaths of three people were attributed to the storm in England, the corresponding death toll in Chennai was a devastating 500.

This stark difference in the impact on a city in a developed country compared to one in a developing country underlines how the response to climate change needs to be different for different urban environments. There is no ‘one size fits all’ solution to climate change. It is therefore critical that action plans are tailor-made to the circumstances and vulnerabilities of individual cities.

Cascade failures
A major vulnerability is the interconnectivity between systems and services that feed and support cities. This leads to the prospect of cascade-type failures, namely a failure in one system triggering a failure in another.

A study published by the Royal Academy of Engineering (ii) reveals that Lancaster escaped extreme flooding during Storm Desmond but nevertheless experienced disproportionately wide-ranging disruption in terms of loss of power and communications when a single substation was shut down as a prevention measure against flooding.
It shows how when taking steps to strengthen the resilience of cities, it is no longer sufficient to look at assets in isolation. It is vital to identify interdependencies and ripple effects which can result in cascade failures and protect against them where it is cost-effective to do so.

Building higher flood defences is certainly part of the solution to flood risk management. Carlisle’s newly installed £30M flood defence barriers, designed to withstand a one in a 250 year event, may have been overtopped but at least they succeeded in delaying the floods, giving time for the emergency services to react and helping to preserve life.

Barriers, however, can generate a potential sense of complacency. If you invest in physical protection, why would you need to invest in contingency planning and disaster management as well? The obvious reason why is that not all flooding can be prevented, so infrastructure should be designed with built-in flexibility and redundancy. If and when the unthinkable happens and essential systems are inundated, they must be capable of rapid and safe recovery.

Resilience funding
Those cities that have suffered the most from recent climate shocks are unsurprisingly spending the most on climate resilience, be it preventive or recovery measures. But overall we are not investing anywhere near enough.

We are only spending millions on resilience when the effects of climate change will require billions. In other words we are investing 0.1% of what we need to safeguard our cities over the coming decades.

Innovative ideas to unlock new sources of funding are urgently needed. A good example is the dual-purpose SMART stormwater tunnel in Kuala Lumpur. In order to generate a return on a major capital investment and attract investors, the central section of the tunnel doubles up as a toll motorway (when it’s not raining of course) thus providing flood protection and alleviating traffic congestion.

The world has to find more ‘smart’ ways like this to manage flood risks and bridge the substantive funding gap. Half the world’s population live in cities and that statistic is only going in one direction.

Urbanisation continues to be driven by economic and social development, population growth, economic migration – and migration brought about by climate change itself.

Ironically, poorly planned urbanisation itself can contribute to climate change through increased consumption and pollution, creating a potentially dangerous feedback loop. If we don’t get the planning of our cities right, there is a real danger that urbanisation will multiply the risks of climate change, and contribute to a rise in global temperatures that would lead to entirely unsustainable economic losses and catastrophic impacts on the populations that cities aim to support and protect.

This article is based on the presentation Ian gave at the NCE’s Flood Management Forum in London in October 2016.

(i) Stephane Hallegatte, Colin Green, Robert J Nicholls and Jan Corfee-Morlot (2013), Future Flood Losses in Major Coastal Cities, In Nature Climate Change, 3, 802–806, Macmillan, London.

(ii) Lancaster University, Royal Academy of Engineering and Institution of Engineering and Technology (2016), Living without Electricity: One City’s Experience of Coping with Loss of Power, Royal Academy of Engineering, London.

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