Cumbrian flood anniversary

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  • Cumbrian flood anniversary
    19.11.2010 15:49

    A year ago between the 16th and 20th of November 2009, heavy rains and gales hit parts of north-west England. The worst affected area was Cumbria, where, after having already nearly received November’s average rainfall, a record breaking rainfall event fell onto already saturated ground.

    The UK records that were broken were for consecutive rainfall days (0900-0900GMT) with the highest 2, 3 and 4 day totals all broken. In the 2 day period from the 18th to 19th of November, Seathwaite recorded 395.6mm (378mm of which fell in just 34hours), the 3-day period from the 17th to 19th it recorded 456.4mm, and the 4 day period from the 16th to 19th 495mm of rain fell.

    The weather that caused this extreme rainfall event was the result of a deep area of low pressure tracking slowly north-eastwards between Scotland and Iceland. This resulted in a warm, moist south-westerly air flow across the UK along with an associated slow moving weather front that sat over northern England for around 36hours.

    The airmass had tracked north from areas of much higher sea surface temperatures to the south of the Azores, ensuring the air was rich in moisture. As it reached the higher ground in western areas of the UK it was forced over the higher ground. As the air rose over the Cumbrian fells it cooled causing the moisture to condense and fall as rain.

    As the rainfall flowed off the fells and down into the rivers floods were inevitable. A total of 2239 properties throughout Cumbria were flooded, with around 80% of these being residential properties. The worst-hit area was affected by flooding from the River Derwent. In Workington, a police officer died after the A596 road bridge collapsed, leaving the town cut in half as the remaining road bridge in the town had also been severely damaged.

    Cockermouth was also badly affected as the town centre became submerged in over two metres of floodwater. One success was the flood defences in Carlisle which after being built after the floods in 2005, held up against the waters.

    In comparison, the recent flooding in Cornwall was the result of a different kind of weather set up, but again it was from a low pressure that was initially subtropical and the rainfall was also enhanced by the already saturated ground and also topography of the local area. The rainfall totals were nothing like the scale of last year in Cumbria, with the highest total at Cardinham on Bodmin which received 50mm overnight on Tuesday and into Wednesday morning.

    However, 80mm was recorded at an environment agency rain gauge at Collingford reservoir. The rainfall here was as a result of an occlusion moving from the west, but with a locally intense narrow band of line convection which gave 18.8mm in just one hour at Cardinham. The flooding forced over 100 people to be evacuated from their homes.

    The forecast for the coming days brings another area of rainfall and fresh winds across south-western areas on Friday night, some of which could be heavy for a time before easing by Saturday.

    By: Stephen Ellison