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Will London Flood in the Future?

The U.K. has had its fair share of floods. Many have been caused by violent and sudden downpours, whereas others have been the final call on an Atlantic storm’s whistle-stop tour.

Perhaps the worst, however, came during the winter of 2013/14, when a series of Atlantic storms caused widespread power cuts, disrupted major transport lines, and destroyed homes. Five years on, the question of where the next major flood will occur remains an open, and disconcerting, question.

One major factor to take into deep consideration is climate change. As global temperatures increase, the risks of tidal flooding become ever-more likely. Significantly, one of the UK’s primary flood risks sits along the Thames Estuary, in England’s capital city. With 1.3 million people and £275 billion worth of property and infrastructure at risk, there is a lot to lose from another flood.

Enter, the Thames Estuary 2100 Plan (TE2100). Published by the Environment Agency in 2012, it sets out how we can manage tidal flood risk in the estuary, from now until the end of the century. Monitoring changes in the estuary and assessing the options available, the Environment Agency and partners hope to minimise the impact of rising sea levels, tidal surges and erosion until the year 2100.

Inspired by the Crystal’s Future of Cities exhibition, and with help from leaders within the Environment Agency who established the Thames Estuary 2100 Plan, we look at how tidal flood risk is being managed in the capital.

Why is London at risk?

The Thames has experienced a number of major floods since the turn of the 20th century. The most disastrous of these occurred in 1953, when water reached ceiling level in coastal homes. Over 100 people lost their lives and the damage to property cost the equivalent of £1.2 billion in today’s money.

This particular storm saw its origins not on land, but in the North Sea. Bands of low pressure (called depressions) moved down the east coast of England, causing the sea beneath to rise and thus create a raised surge of water.

Due to the unique character of the capital, tidal surges typically grow higher as they are squeezed between the coastline and mainland Europe. The result of this is a bottle-neck in the Thames Estuary which, when surge tides take hold, can increase water levels by between 1-3m.

Following the floods of 1953, a government committee devised a new barrier, along with raising flood walls along the estuary, which aimed to prevent similar floods in the area. The Thames Barrier, still the second largest movable flood barrier in the world, opened in 1983 and remains one of the most effective precautions at present.

The Thames Barrier

Spanning 520 metres and standing five-storeys tall, the barrier is designed to prevent North Sea tidal surges from reaching land. Without the barrier and its associated defences, London would have between a 2-10 per cent chance of tidal flooding occurring in any year; with the current defences in place, this reduces to 0.1 per cent chance of tidal flooding occurring in any given year.

In recent years, however, questions have been raised about how the barrier (designed more than 30 years ago) will cope with the growing effects of global warming. For instance, during the winter of 2013/14, the barrier closed 50 times (see: graph) – a huge increase on the infrequent barrier closures of the 80s and 90s.

And it is these climate change trends which alarm environmentalists. They predict that, by the year 2030, the barrier will need to close around 30 times if it is going to block future tidal surges sweeping in from the North Sea. This is something the barrier is not designed to uphold.

“Flood damage could cost London £80bn”

But the threat doesn’t simply start in 2030. In fact, it’s already begun. The high water mark over London Bridge has gone up by over 1.5 metres since 1780. This, coupled with the south of England’s slowly sinking land mass, could therein spell trouble.

To make matters worse, many parts of the capital are built on a tidal floodplain, meaning a flood could impact more than 1.3 million people (around a sixth of London’s population). The cost of this damage, environmentalists and economists predict, could reach £80bn if nothing more is done to protect the capital today.

The Thames Estuary 2100 Plan

To manage tidal flood risk from the Thames, the Environment Agency developed the Thames Estuary 2100 Plan. The Plan looks at the river’s current flood defence systems and sets out an ever-evolving strategy to maintain and improve these defences, with the aim to minimise tidal flood risk in the London area.

Designed to adapt to changes in predictions for sea-level rise and climate factors, the Plan aims to work with nature, rather than against it. Currently, the Plan is based on a relative sea level rise estimate of 90cm by 2100, but is adaptable to differing rates of sea level rise up to 2.7m, and an increase of 40 per cent in peak river flood flows.

There are three phases to the Plan. The first phase, which lasts until 2035, focuses on maintaining and improving current defences, safeguarding areas required for future improvements, and monitoring climate change indicators. The second and third phases of the Plan will put more emphasis on raising defences and determining the future of the Thames Barrier, to enable London and the Thames Estuary to adapt to further increases in sea levels.

“We cannot do this alone”

And, while the Environment Agency takes a lead role in delivering the Plan, Simon Moody, Environment Agency Area Director for London, sees flood defence as a joint effort:

“We cannot do this alone. We need to work in partnership with riverside owners and particularly local councils. Their spatial planning function is key to creating a riverside which can continue to manage the future tidal flood risk to communities and businesses.”

Drainage alternatives

Another major risk to the capital is from surface water flooding. This occurs when prolonged heavy rainfall hits urban areas and does not drain away quickly enough. Areas with high-density development and a lack of green spaces are particularly prone to surface water flooding.

One solution to this is SUDS (Sustainable Urban Drainage Systems). SUDS create soakaways which slow the flow of run-off rainwater, thus reducing the likelihood of flash flooding.

Some councils are already managing surface water flooding in their area with their various actions. For instance, they recommend developers replace impermeable materials, such as tarmac pavements, with permeable materials, such as gravel or grass to allow excess rainwater to seep into the exposed surfaces. This could potentially reduce surface water flooding in high-risk areas.

Here at the Crystal, we are ideally placed to discuss the Thames’ flood defence systems. For more information on flood risks in the U.K., bring your school or university along to the Crystal’s Future of Cities exhibition.

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