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Vulnerability of coastal cities: examples of London and Venice

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Introduction

Many coastal cities are vulnerable to sea level rise and storm events. European examples of cities likely to be affected by climate change include London and Venice.

London and the Thames Estuary

London and the Thames Estuary are vulnerable to sea level rise, storm surge, flooding in the upstream tributaries of the Thames Rivers, and heavy rainfalls. All these factors and potential negative impacts have been aggravated by increased building in the flood plain, decreasing the absorption of rainfall and inadequate sewage and storm water drainage systems. In its period of operation, the Thames Flood Barrier has been used to reduce the impact of upstream flooding as well as tidal surges. An extensive study is now occurring under the Thames 2100 initiative to determine additional flood and tidal surge defence mechanisms that will be needed in the near future to address climatic sea level rise and extreme weather events. London and the Thames Estuary are currently protected to a high standard (generally 1:1000 years or 0.1% at the year 2030). The design of the Thames Barrier allowed for sea level rise but did not make any specific allowance for changes due to climate change in fluvial flows coming down the Thames or the size of storm surges arising in the North Sea. Rising sea level and rapidly increasing development within the tidal flood plain mean that flood risk is increasing and by the year 2030, improved arrangements will be required if flood protection standards are to be maintained at present levels.

Venice and the Venetian Lagoon

The Venice lagoon, the infrastructure and the communities are very vulnerable to sea level rise and storm events, with natural and human-induced vulnerability increased by climatic changes. Venice is not only threatened by high tides, but is sinking through subsidence, at the same time as the Adriatic Sea is rising. The surrounding marshes, which used to break the waves coming into the city, have gradually disappeared, due to the absence of replenishing sediment deposits. Industrial development on the mainland has added to the increased subsidence and pollution.

Venice and the Venetian lagoon, of which the city is one integral part, are vulnerable to both extreme weather events and "normal" flooding, which now occurs up to 10 times in one year. Due to the subsidence of the lagoon (human induced and geological), as well as overall subsidence in the Adriatic Sea, Venice and the Venetian lagoon are also vulnerable to even a 10 centimetre increase in sea level, and will be dramatically affected by a large increase in sea level. The Moses project, which is comprised of 9 barriers, was approved in 2003, is now estimated to cost more than 5 billion euros, and is designed to rise from the seabed to block the inlets of the Venice lagoon from the Adriatic Sea when high tides are forecast. Given the sensitivity of Venice and the overall lagoon to climate change, it could also be considered as a model and indicator for global impacts of climate change for lagoons and coasts.


References

Case Study: Climate Change and European Coast and Beach Management, 2006, Completed by M.A.K.Muir for EU-funded Coastal Practise Network (CoPraNet)
The main author of this article is Magdalena Muir
Please note that others may also have edited the contents of this article.