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ARCHIVE: Tsunami Risk to UK

The policy of successive governments has been to reduce the major risks from tide and weather related events. Coastal flood defences have been hugely improved since the terrible 1953 floods in which 300 people lost their lives. A system of flood warning is in place to warn people in areas at risk and emergency plans are regularly exercised.

The tragedy which occurred on 26 December 2004 when an undersea earthquake caused a tsunami which devastated coastal areas in parts of south Asia heightened public awareness of the possibility of a similar event in the UK. It is important first of all to understand that such an event in the UK is highly unlikely. Nevertheless contingency planning should be carried out in order to try to minimise the effects of rare events - plans which we all hope will never in fact need to be put into effect in a real-life situation. We must of course learn from the Asian Tsunami disaster and ensure that detection and warning arrangements for natural hazards, both globally and for the UK, are as robust as is reasonably possible.

Defra Reports

It was recognised that, although the tsunami threat to UK was assumed to be very low, Defra did not have a comprehensive assessment of coastal flood risk from such events. In February 2005, we therefore commissioned a consortium of leading UK institutions, led by the British Geological Survey, to assess the potential for tsunami-type events originating in all areas of the North Sea and North Atlantic and to consider their potential for generating waves that would be damaging in the UK.

The 2005 report, "The threat posed by Tsunami to the UK", concluded that there are a number of possible, though rare, circumstances in which tsunami-type events with an effect on the UK could be generated by seismic or landslide events. For most scenarios the report suggests that wave heights produced at the coast by tsunami-type events are unlikely to exceed those anticipated for major storm surges. All major centres of development on coasts and estuaries have defences that have been designed to withstand such surge waves.

We accepted the need to carry out further work where some of the uncertainties in this report could be reduced by limited further investigation. A further study, entitled "Tsunamis - assessing the hazard for the UK and Irish coasts", was published in June 2006 and reviews in more detail two of the source Tsunami origins identified in the 2005 report, with their consequence compared to an assessment of hazard.

Further work is under way on improved access to European near-real time tide gauge data for storm surge modelling and Tsunami warning and on development of seismic methods to identify tsunamigenic events and generate data.

You can download the full reports but be aware these are very large files. You are recommended to download sections instead:

The threat posed by Tsunami to the UK (2005)
Tsunamis - assessing the hazard for the UK and Irish coasts (2006)

(All these documents are in Adobe Acrobat (PDF) format. Further information about reading PDF documents can be found on the Defra Help page (see link at bottom of page)).

Emergency Management

The UK's long-established principles of integrated emergency management are applied by all levels of government in planning for disasters. The aim is to ensure that planning arrangements are integrated both within and between organisations and are an integral part of departmental and organisational planning. The UK Reslience website has more information.

Any additional plans for specific detection, warning and forecasting system developments will have to take account of the practical limitations of all warning and response systems in relation to extreme events. These include:

  • The very short warning times likely to be available;
  • The fact that a high degree of probability of identifying extremes necessarily produces a high rate of false alarms. This false alarm rate is greater for more rare events.
  • Major evacuations (if required) inevitably cause significant disruption and severe economic and human consequences (including the potential for loss of life).
  • Any decision to order evacuation in the face of a major disaster is likely to have to be taken by designated duty officials within a relatively few minutes of the initial notification often with very little certain information about the potential outcomes.
  • Such decisions are only likely to be effective if there is clear guidance and well-rehearsed plans, which are difficult to achieve for the full range of potential extremes.

Background

Tsunami are caused by rapid movements of the seabed or of the water column above it, which either lift the sea surface up above its normal level - the usual case- or depress it. The last major earthquake that took place in the central North Sea region took place in 1931 and did not generate a Tsunami.

Risks to the UK from Tsunami-like long wave events differ from the Indian Ocean because of the position of tectonic plates. Whilst they have a relatively low probability, the UK is not immune from the effects of long wave events. There has been a lot of research into the potential for Tsunami type events around the world and the North Atlantic is recognised as one of those areas where such events could happen, and probably have occurred in the last few thousand years. Particular research has identified the possibility of an event originating in the Canary Islands but there are also other potential sources in the area.

Page last modified: 13 November 2008
Page published: 23 March 2005