A river floods when heavy rainfall or melting snow produces more water than the river can hold. A river may also flood if it becomes blockeded.
The River Thames has a history of flooding. When a river floods a lot of damage can be done to homes and the land.
Heavy rain or sudden snow thaw upstream can cause flooding, even in London.
Christmas 1927 saw heavy falls of snow in the Cotswolds where the River Thames has its source. In early January 1928, a sudden thaw doubled the volume of water flowing down the Thames and this, coupled with violent storms, led to London flooding. When the tide turned on 6 January it surged back upstream pummelling the river banks.
In the early hours of 7 January flood waters poured over the top of the Thames Embankment and part of the Chelsea Embankment collapsed. The Flood water destroyed homes and forced local residents to swim for their lives - 14 people were unable to escape and drowned.
The 1928 flood was the last major flood to affect central London and led to the implementation of new flood-control measures, culminating in the construction of the Thames Barrier in the 1970s.
Strong winds can blow sea water up the Thames and cause dangerous floods.
In 1953 a bad storm pushed a lot of sea water into the mouth of the Thames. Around 300 people drowned, as well as 11,000 cattle, 9000 sheep, 2400 pigs, 34,000 poultry and 70 horses. The flooding affected 160,000 acres of farmland, 24,000 houses, 200 major industrial premises, 200 miles of railway, 12 gas works and two large power stations.
Action is needed to prevent flooding.
Thames Flood Barrier
To prevent London flooding the Thames Barrier was built across the Thames at Woolwich at a cost of around £535 million. It became operational in October 1982 and was opened Her Majesty The Queen on 9 May 2004. The Thames Flood Barrier is a tidal barrier which prevents the sea from coming in on really high tides.
The width of the Barrier from bank to bank is about 520 metres (a third of a mile).
Defence Walls in London
London is also protected by 150 kilometres (94 miles) of flood walls and embankments. A high wall runs almost all the way along the Thames in London, except for a few high spots where it’s not needed.
Flood Relief Channel
The Jubilee River is a 7 mile long flood relief channel which was built during the 1990s to divert flood waters from the River Thames around Maidenhead, Windsor and Eton. Despite being man-made, the Jubilee River was designed to look and act like a natural river. It is as big as the Thames and meanders its way along between shallow reed beds. Along the river there are 5 weirs.
Did you know? .....
London is sinking at an estimated 12 inches (30cm) every 100 years.
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