Transcript Carlisle Case Study

Carlisle Case Study
Using an Atlas, describe the location of Carlise.
Using the Key geography textbook pages 81+82; Identify the location of
the River Eden.
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Carlisle Case Study
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Carlisle is situated on the flood plain of the River Eden with three rivers
meeting in the city. The catchment covers approximately 2400km2 and is
home to approximately 244,000 people. The catchment is mainly rural, with
only 1% classified as urban: the main urban areas are Carlisle, Penrith and
Appleby.
Carlisle has a history of flooding with flood events recorded as far back as
the 1700s. In recent years there have been significant floods in 1963, 1968,
1979, 1980, 1984, and recently in 2005.
Across the catchment, the January 2005 flooding affected 2,700 homes. In
Carlisle three people died, 1,844 properties were flooded and there was
significant disruption to residents, businesses and visitors. The cost of the
flooding was estimated at over £400 million. The flooding followed
prolonged heavy rain, and was caused by a combination of floodwater from
the Rivers Eden, Pettereril and Caldew and localised flooding from sewers
and road drainage.
Carlisle Case Study
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The catchment of the River
Eden is in Cumbria, rising in
the hills of the Lake District.
It reaches the sea at the
Solway Firth. The catchment
is made up of the Rivers
Eden, Eamont, Irthing,
Petteril and the Caldew, as
well as smaller rivers and
streams draining into the
Eden estuary.
Carlisle Case Study
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The upper parts of the catchment are dominated by the mountains of Skiddaw and the
surrounding fells. The rocks here are hard and volcanic, soils are thin and the gradients of many
tributaries are steep, so these watercourses have a rapid run-off response to flooding. In the lower
reaches rivers flow through wide, shallow valleys.
The Eden channel itself has a steep gradient upstream of Kirkby Stephen. The head of the
catchment is around 690m, falling rapidly to 160m at Kirkby Stephen. Below Kirkby Stephen, the
Eden's glaciated valley opens out and the channel gradient reflects this change: the River Eden
steadily loses height at around 1.8m per km to Appleby at 123m some 21km downstream.
From Appleby, the Eden continues through the lowland valley to Carlisle, 9m, falling at a fairly
constant rate of 1.4m per km over its 80km journey from Appleby. The valley floor is over 2.5 km
wide in many places. This forms extensive areas of floodplain washlands which are an important
feature of the catchment.
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Hydrology
In the Eden catchment there is a significant contrast in mean annual rainfall between the upstream
and downstream ends of the catchment, related to the topography of the catchment.
In the upland tributaries upstream of Penrith in the Eamont catchment, average annual rainfall
exceeds 2800mm on Helvellyn
Around Carlisle and on the coastal fringe, this is reduced to about 760mm
The average annual rainfall for England and Wales is 920mm.
Carlisle Case Study
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In the steep upper catchments the topography, combined
with the geology, leads to fast responses to rainfall:
In Kirkby Stephen, the River Eden will respond to rainfall in
around 1.5 hours The time taken for rain falling on the top of
Helvellyn, the highest point in the Eamont catchment, to
reach Ullswater Lake is around 2 hours
In the lower catchment, with mainly lower gradients and
deeper soils, the flood responses are slower.
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The January 2005 flood was a major event.
Rainfall was very high for the period 6 to 8
January, during which two months' worth of
rainfall were released in 24 hours. However, it
followed a month of high rainfall in the
Carlisle area, so the ground was saturated
and would no longer allow water to infiltrate,
and surface run-off was excessive. The result
was rapidly rising water levels in a number of
rivers including the Eden.
Affects of the flooding
 http://www.geography.org.uk/download/GA
_FloodingCarlisleDepthSequence.gif
Carlisle Case Study
Carlisle Case Study
Carlisle Case Study
Carlisle Case Study
Hydrograph for River Eden near Carlisle, January 2005
Rainfall in mm
Flow m3/sec
Rainfall mm
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Flow cubic metres/second
60
Tasks
Date
1 Annotate the hydrograph to show you understood these terms: rising limb,
falling limb, peak flow rate, lag time, recessional limb
2
Read the text: What was the hydrology of the January 2005 flood? Then
add text boxes to the hydrograph with brief notes about key aspects of the
flooding - use the dates on the hydrograph to help you.
3
Using the map in the text book, use map evidence, explain the physical and
human factors which may have contributed to the flooding in Carlisle. 6 marks
4
Using the hydrograph and your understanding of the drainage basin
characteristics of the River Eden, describe and account for the flood
hydrograph shown for January 2005. 10 marks
Carlisle Case Study
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Physical Factors
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Low lying flood plain less than 20m
Many tributaries joining the Eden e.g. River Petteril 412564
Lack of evidence of vegetation on the map, this limits interception rates.
Higher than average rainfall
High drainage density
Human Factors
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Homes built on the floodplain (wet point site) Edentown 3957
Levees along river banks may have been artificially strengthened
Recreational activities deliberately built on the floodplain e.g. golf course
414565
Impermeable surfaces increasing surface run-off created by the urban
environment of Carlisle.
Sewage works at 320505