Transcript Introduction to the London Borough of Lewisham. The London

Introduction to the London Borough of
Lewisham.
The London Borough of Lewisham is
situated in the south east of London,
including the areas of Lewisham,
Deptford, and Catford. A fifth of the area
of the Borough is green space, the rest is
highly urbanised. It is bordered by
Greenwich, Bromley, Southwark, and
Tower Hamlets north of the River
Thames.
Lewisham Key Fact.
There are approximately 21,000
properties at risk of flooding in Lewisham
but over 80 per cent have a low likelihood
of flooding. Over 5,000 of the properties
at risk are signed up to receive the
warnings from the Floodline Warnings
Direct or Extended Flood Warning
services.
Flood risk and Flood zones.
Reasons for risk.
Low lying land.
Many rivers and streams
in a small area a high drainage density.
River Thames – is tidal.
Global warming – wetter
summers and winters.
Impermeable surfaces –
urbanisation – a
population of approx.
250,000.
Steep-sided channel
Increased speed of water flow
e.g. sloping roofs, storm drains
River confluences
(increase amount of
water arriving in a
short time).
Impermeable Drainage Basin –
e.g. concrete in urban areas
Causes of Flooding
Coincidence with
high tide
Land drainage
e.g. for agriculture,
housing
Extreme weather
e.g. a month’s rainfall in
2 hours (Boscastle)
High rainfall previously
saturating ground
Deforestation
Flood risk and Flood zones.
Flood risk and Flood zones.
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In Lewisham there are approximately 21,000 properties at risk of flooding from
river and tidal sources.
This equates to 16 per cent of all properties in the Borough.
For the properties at risk of flooding, 8 per cent are classified as having a
significant likelihood of flooding.
83 per cent which are classified as having a low likelihood of flooding. The
remainder have a moderate likelihood of flooding.
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The London Borough of
Lewisham has some land within
flood zones 2 and 3.
Flood zone 2 represents the 1 in
1000 year probability of flooding.
Flood zone 3 represents the 1 in
100 year probability of flooding.
The area of land within flood
zones 2 and 3 is predominantly
around in the North of the
Borough, where the risk is tidal
flooding from the Thames.
Other areas include the land
around the river Ravensbourne
and river Pool, extending to the
south of the Borough and the
Quaggy, extending towards the
east of the Borough.
Historical floods.
Fluvial (river) and tidal flood
events
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Flooding has not occurred in
Lewisham since 1968, when
there was large scale flooding
through Lewisham and Catford
town centres.
There was also some flooding
around Bell Green, Southend
and Grove Park. This was
flooding from the River
Ravensbourne.
Previous flood events occurred
in 1928 and 1965. In 1928,
there was some overtopping of
the tidal defences by the River
Thames which caused some
flooding in the north of the
Borough.
The event in 1965 was similar
to 1968 but on a much smaller
scale.
Risk awareness.
• Flood warning
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In the Borough of Lewisham there were 5,083 properties registered to receive
flood warnings as of June 2010.
Of these 4,539 properties were identified by the Environment Agency as being in
areas of flood risk. If flooding is expected the residents of these properties will
receive an automatic warning from the Extended Direct Warnings (EDW) service
via their landline telephone.
The residents of the remaining 544 properties registered to receive flood warnings
opted to receive them from Flood Warnings Direct (FWD). The Environment
Agency offers this free flood warning service, which gives advance warning of
flooding via phone, text, email, pager or fax.
• Sign up for free flood warnings at http://www.environmentagency.gov.uk/homeandleisure/floods/38289.aspx