UK Flood and Sinkhole Risk Continues: AIR

February 26, 2014

This winter has been the wettest in the United Kingdom since detailed data was first published in 1910, and the rainfall total for January was the highest recorded since 1766, according to catastrophe modeling firm AIR Worldwide.

Beginning with a powerful storm in late October 2013, a series of severe winter storms contributed to exceptional rainfall accumulation over an extended period and resulted in extensive flooding. Between December 1 and February 19, the UK had 486.8 mm (19.2 in) of rain, with record amounts falling in Wales, east Scotland, and across the south of England. Large areas were hit with more than twice their seasonal average, and many rivers in southern England reached their highest ever recorded levels.

“The flooding crisis deepened with the arrival of yet more severe weather between February 10 and 14, but across much of southern and central England the risk of flooding is now receding as river levels fall,” said Shane Latchman, senior research associate, AIR Worldwide. “Significant flooding issues remain, however, and along stretches of the Thames properties in Windsor and Maidenhead, Surrey, Buckinghamshire, Wokingham and West Berkshire may remain flooded for some time. The wet weather has also created perfect conditions for sinkholes, which are being reported at between five and ten times the normal rate this month.”

As of noon on February 26 there were still 2 severe flood warnings, 15 flood warnings, and 91 less serious flood alerts in place in England and Wales and 6 flood warnings active in Scotland. Both of the severe flood warnings still in place in England are in effect in the Somerset Levels, where a high overall flood risk remains and severe river flooding will continue. The Somerset Levels and Moors, as the region is properly known, covers about 65 square miles and is one of the lowest and flattest parts of the country. Much of the area lies at or below mean sea level and its highest points are only 8m (25ft) above it. The catchment is largely pumped, and relies on man-made interventions and sea defenses. In the country’s largest ever pumping operation more than 65 pumps, some specially imported from the Netherlands, are currently working to remove millions of tons of water from the Levels every day.

The Army has begun a “rapid inspection” of flood defenses to assess the damage to them.

According to AIR, this winter’s storms have caused extensive coastal erosion in the form of crumbling cliffs, shrinking beaches and sand dunes, and breached sea defenses, with some locations reporting several years’ worth of damage in the space of as many weeks. On the coast of Mid-Wales, beach erosion has exposed a forest of Bronze Age tree stumps. Nearby, and in southwestern England it has also exposed some rather more dangerous relics in the form of unexploded World War II bombs and a live World War I mine.

According to the Environment Agency more than 5,800 homes and businesses have flooded since the beginning of December, however 1.3 million properties have been protected by flood defenses. Many thousands of households have been evacuated.

Latchman noted, “The January rainfall in England was greater than the rainfall that induced the devastating floods of July 2007, but it came in the winter, which is generally a much wetter season. The number of homes damaged and the estimated total costs associated with this winter’s flooding are lower than in 2007, for which the Association of British Insurers estimated the insured losses alone to be more than GBP 3 billion.”

Latchman concluded, “Groundwater is continuing to rise and another storm system is expected to strike on Thursday, bringing unusually heavy rainfall to western parts of the UK. With more unsettled weather anticipated, the risk of flooding will be slow to disappear and the flooding in parts of Greater London, Kent, Hampshire, Wiltshire, Somerset, and Dorset will continue. In the Somerset Levels the dredging of key stretches of waterway will begin before the end of March, provided water levels drop and the land is dry enough to support the equipment.”

Source: AIR Wolrdwide

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