Lesson 6 causes & frequency of flooding
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Transcript of Lesson 6 causes & frequency of flooding
Starter
Person A – Describe how a waterfall is formed.
In pairs
Person B – Describe how meanders and Ox Bow Lakes
are formed.
Do you know what happened here?
http://www.youtube.com/watch?v=ewTVKR_ZFhU
The causes and frequency of flood events.
Aim of the lesson:-
To find out why floods occur and how often they can happen.
By the end of this lesson you
should be able to:-Knowledge
• To know why floods occur.
Understanding
• To understand the different causes of flooding and how they can be grouped into physical and human.
Skill
• To be able to annotate photographs effectively and complete graph work.
Floods occur when a river bursts its banks if it is carrying so much water that it cannot be confined
in its usual course.
Usually big floods occur less often and less severe floods
occur more frequently.
The effects of flooding
The frequency of flood events in the
UK
Are we getting more and more floods in the UK?
Flooding appears to becoming an increasingly frequent event. In 1607, a great flood affected Devon, Somerset and South Wales. Major floods however were infrequent in the UK. In March 1947, major floods did occur, affecting many areas of southern, central and north eastern England, including York, Tewkesbury, Shrewsbury, Sheffield, Nottingham and London, following the rapid melting of snow. The combined effects of storm surge and high tides, contributed to the floods of January 1953 that hit the east coast including Suffolk, Essex and Kent, when huge waves washed away sea defences and 307 people died. In 1968, another great flood affected counties in south east England.
After this time, there is little mention of major floods until relatively recently, when they have regularly made the headlines. Since 1998, floods have been an almost annual occurrence.
Most people agree that the frequency of damaging floods in the UK is increasing
Why??
Some blame climate change for more extreme weather events
Others blame planners for allowing houses to be built on flood plains
Weather experts point out that weather across the British Isles is highly variable; wet summers (like 2008 & 2009) happen when frontal depressions hit the UK by tracking further south than normal.
Flooding 2012
http://www.youtube.com/watch?v=MLqVQoL4JmE
Other flood events in the UK
Morpeth floods 2008In early September the River
Wansbeck, which flows through the town centre, could take no more after a wet summer, & a
particularly wet August was followed by more than the whole of September's rain
falling within 48 hours.
Morpeth, Northumberland 2008
The heavy, persistent rain came from an active area of low pressure, which spent the weekend over
north-east England, moving only a little.
Yorkshire Floods in 2007
The summer floods of 2007 affecting south & east YorkshireA prolonged period of wet weather, much higher than average rainfall, & concentrated periods of heavy rainfall, all of which precipitated the very serious local flood events. A year later, many of the affected households had still not fully recovered.
3 marks
There may be reference to what flooding is – that rivers flood when they burst their banks.
Allow 1 for this, but emphasis should be on underlying causes such as building towns on floodplains and creating an impermeable surface so that water cannot infiltrate and thus flows quickly over surface to river, reducing lag time.
There should be recognition of the factor from the information and this then needs using to explain the sequence of events that cause flooding. May refer to only one cause or two or more.
And the marks scheme says . . .
3 marks
Homework
Learn your key
words for next
lesson.