Current Coastal Flood Defences From Around the World

Coastal flooding is not a new problem and so some defences are already in place to protect human settlements from inundation; this post documents two of the most interesting examples.

Thames barrier, London

Opened in 1982, the Thames barrier is one of the worlds largest movable flood barrier [1], the 520 meter barrier spans the River Thames and protects some 125 square kilometres of London from flooding [1]. 

Such flooding would be the result of a storm surge travelling up the river Thames, the type of which hit London, during the Great North Sea Flood of 1953 and was the actual cause of the construction of the Thames Barrier. The North Sea Flood killed a total of 307 people across the South East of the UK [2], a death toll that would have been much higher, had the force of the wave not been deflected by the Netherlands, on its way to the Thames Estuary. Please see the following video, for a BBC view on the matter.

The use of the barrier, which cost £0.5 billion pound to construct and consists of 10 steel gates that can be raised to prevent high tides and storm surges from inundating London [1], has been increasing on a annual basis, since it became operational [3] (figure 1).

Figure 1: Number of annual closures of the Thames Barrier to protect London [3]

As can be seen from figure 1, apart from a few years of lag, the number of closures have been generally increasing since the beginning of operations. Such a trend raises questions of the barriers ability to protect London in the future and what, if any changes should be made to the protection of the UK's capital. The next post will discuss such matters. 

The Netherlands

The Netherlands is in a unique and hugely compromising physical position, in relation to the sea. 26% of the country is below sea level, 70% of the country would be flooded without coastal defence and 70% of the GDP of the Netherlands is produced in areas below sea level [4]. It is because of this, that the Netherlands coast is lined with man made dykes, sea walls, coastal dams and flood gates, in an effort to stop the sea. 

One example of such defences can be seen in the village of Petten, which is currently protected from the sea by a 13 meter high and 46 meters thick sea wall [5]. This wall has been increased in height by the Dutch authorities, since its construction in 1976 [5] and is another example of the relentless and increasing threat of rising sea levels.

A second example of Dutch coastal flood defences can be seen in the city of Rotterdam; a city that has to compromise between maintaining a prosperous port and preventing the flooding of a vulnerable area. A resolution of this problem was found in a swinging gate system that can be closed across the shipping channels when a storm surge is approaching the city. 

Please see the following video, for a detailed explanation of the system and altered channel floor, I have included Dutch subtitles, for my international fans. 

As the video explains, the efforts that have been taken to prevent flooding of human settlements have advanced, both technologically and in terms of costs. With sea level rise potentially accelerating, we must now ask ourselves how much longer we can hold off the advancing seas.  

The examples given during this post document the extreme lengths governments are willing to go to to protect areas of land from inundation. There is however a growing train of though, promoting managed realignment of coasts to allow natural defences to reform. The next post will document such thoughts and ask what changes, if any, should be made to the current system.

Reference List

[1] The Environment Agency, 2011. The Thames Barrier [online]. Available at:  http://www.environment-agency.gov.uk/homeandleisure/floods/38353.aspx [26.4.2011]

[2] Henry, E., 2007. Sever Flooding 'Could Put Lives at Risk' [online]. Available at: http://www.martinfrost.ws/htmlfiles/nov2007/1953flood.html [26.4.2011]

[3] King, D.A. ,2004. Climate change Science: Adapt, Mitigate or Ignore? Science. 303. 176-177

[4] Waterland Information Network, (n/d). Dutch Flood Control and Protection [online]. Available at: http://www.waterland.net/index.cfm/site/Water%20in%20the%20Netherlands/pageid/E3B3B416-FB4E-0AB8-2FB6E2B271F1BD6E/index.cfm [26.4.2011]

[5] Woodard, C., 2001. Netherlands Battens Its Ramparts Against Warming Climate [online]. Available at: http://news.nationalgeographic.com/news/2001/08/0829_wiredutch.html [26.4.2011]