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JBA and Met Office Winter (2013-14) storms update

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Residential property claims expected to be lower than in 2007

Despite the extreme weather that the UK has been experiencing since December 2013, and the wettest December to January period since records began, claims for flood insurance are expected to be significantly lower than those following the summer floods of 2007.  Current estimates are at around £630 million and could rise to £1 billion.  The figure was nearer to £3 billion in 2007. 

A stream of successive deep lows has resulted in more damage and disruption for areas already feeling the impact of previous storms this winter. The storm surge and wave overtopping experienced during Extratropical Cyclone Xaver at the start of December mainly affected the east coast of England and North Wales, resulting in damage and breaches to some coastal defences. As of mid-January some, but not all, of these defences had been repaired before the February spring tides.

Coastal areas of Cornwall, Devon and Dorset were particularly affected by the storms over Christmas and New Year. Some defences which had been damaged or weakened during late December were still awaiting repair when the most recent storms hit the coast. The repeated cycle of heavy rainfall events on already saturated catchments, both in terms of river flows and groundwater levels, has led to extensive flooding in the Thames Valley.  Since the beginning of December 2013, 5,800 properties have flooded across England. However, 1.3 million have been protected by fixed and demountable defences.



January 2014 rainfall as a % of 1981-2010 average

Meteorological background

The extreme run of frequent winter storms, starting in early December, has persisted throughout January and into February. Hurricane-strength winds and the resulting powerful waves have caused damage along long portions of the South West England coastline. The jet stream has continued to be particularly strong and has remained in a position that is causing deep depressions to cross the Atlantic towards the UK.  In addition, an increase in the intensity of storms can intensify further, the strength of the jet stream. This positive feedback means storms can often cluster together over a period of time.

December was the windiest since records began in 1969, based on the occurrence of winds in excess of 60 kts. Maximum wind gusts of 91 mph were recorded at Berry Head, Devon during the night of 4 February. With sea defences already weakened from Xaver and the successive lows of January, the storms of early February caused serious damage to coastal infrastructure.

In addition to strong winds, the continuous series of deep lows have brought unprecedented rainfall. Figure 1 shows the wettest January for Southern England in at least 248 years . The unusually wet winter has recharged the permeable southern chalk bedrock, leading to persistent and exceptionally high groundwater levels. An Environment Agency flood alert is currently in place for groundwater flooding in Patcham, near Brighton.  Saturated catchments, raised groundwater levels and successive periods of rainfall have resulted in the longest period of high flows on the Thames at Kingston than at any other recorded flood episode. 

Counties affected by January and February storms

South West England coast: protection and damage

The storm of 4 and 5 February caused some localised failures of coastal defences, with 2,000 properties being evacuated in the south west of England. Localised flooding from wave overtopping affected relatively few properties at Dawlish, Perranporth and Plymouth Hoe on 6 February. Whilst damaged defences may not always result in flooding inland, important infrastructure that is protected or built upon defences may be severely impacted. Most notably, around 80m of sea wall was destroyed at Dawlish, causing the railway to remain suspended in mid-air and disrupting travel from London to the South West for several weeks. 

Thames Valley

On 10 February, the Environment Agency issued 14 severe flood warnings along the River Thames in Berkshire and Surrey. Additional rainfall on the already saturated Thames Valley catchment caused significant flooding in villages along the river. Chertsey, Datchet and Wraysbury were particularly affected.  By 13 February, 850 people were evacuated from properties, including residential care homes, by emergency services.

Although the extent and damage caused by flood waters was severe, the number of properties affected is likely to be significantly less than during the 2007 UK summer floods, where 35,000 homes and businesses flooded.  The Environment Agency estimates that for the period 29 January – 12 February, 1,135 homes have been flooded along the Thames Valley, whilst 181,000 properties have been protected by defences. In addition to fixed defences, the Environment Agency deployed 23 demountable defences in communities across the Thames Valley.

Losses

As with other recent storm events, initial estimates of losses are difficult to accurately quantify. 

Fewer properties have been affected than in the 2007 summer floods, where claims cost the insurance industry some £3 billion. For flooding in December and January, early forecasts place losses at £630 million, possibly rising to £1 billion if the rains continue into March and April.  This is still significantly less than 2007.

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