UK flood in 2007

Oxford flood.

Source: FLOODsite, IOER

The “exceptional” floods of 2007, are evaluated in the Pitt Review: Learning Lessons from the 2007 floods: what people need. It was caused by extreme rainfall in the wettest summer since rainfall is recorded in the UK (1766!). The official records show that more than double the usual rain fell in the months of May, June and July in England and Wales.

Water bowser.

Source: FLOODsite, IOER

The consequences were severe. Around 7000 people had to be rescued by emergency services, 13 people died. Some 55.000 properties were flooded. The Mythe water treatment works were out of order for more than two weeks. This caused 350.000 people to be without drinking water from the tap. Bottled water and bowsers were used to supply water to these people. Also a power supply plant was shut down, which left 42.000 people without electricity for a day. Around 10.000 people were left trapped on the M5 motor way. Others were left stranded on railway stations, waiting for trains that could not come becuase of flooded rails. The total economic damage is estimated at over 40 billion pound.

In the UK most flood defences are maintained by the Environment Agency. The rest are maintained by local authorities, internal drainage boards, businesses and individuals. These defenses are mostly designed to withstand floods with a 1 in 100 probability of occurence.

The swelling waters affected about 1000 km over flood defenses. About half of them were overtopped because of the huge amount of water flowing through the rivers. A small length of defences breached, but that had a comparatively small effect on the whole.

The rain in May and early June saturated the soil so little water could infiltrate from the rain that fell in June and July. The Environment Agency estimated that a third of the flooding was due to flooding of rivers and other surface waters. The other two thirds are caused by problems with surface water drainage systems.