Human Activity & River Landscapes (Edexcel GCSE Geography B)
Revision Note
Written by: Bridgette Barrett
Reviewed by: Jenna Quinn
Human Activity & Storm Hydrographs
There are many human activities which change the river landscape
This impacts on the storm hydrograph, changing the lag time and discharge
Human Factors Affecting Storm Hydrographs
Human Factors | Impact | Effect on Hydrograph |
|---|---|---|
Deforestation | Lack of trees reduces interception and infiltration, increasing overland flow |
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Afforestation | An increased amount of trees increases interception and infiltration reducing overland flow |
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River management | Dams can be used to control the level of discharge downstream |
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Urbanisation | Impermeable concrete and tarmac increase overland flow Water flows into the drains reaching the river rapidly |
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Agriculture | Bare soil and ploughing increase overland flow, especially where ploughing is downslope Replacement of pasture (grassland) with arable crops also increases overland flow |
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Climate change | Rising global temperatures may increase storm frequency and intensity, increasing precipitation Increasing drought which leads to baked soil and periods of extreme cold which freeze the soil which means that water cannot infiltrate |
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Deforestation, urbanisation and agriculture all increase the overland flow
Overland flow reaches the river more rapidly than through flow or groundwater flow
This means that the lag time is reduced
They also increase the amount of water which reaches the river
This increases the level of discharge leading to a steep rising limb
The combination of these factors leads to a storm hydrograph which has a rapid response to a rainfall or storm event
Afforestation increases the time the lag time and increases infiltration so less water will reach the river
Worked Example
Explain two ways in which human activities can affect storm hydrographs
(4 marks)
You will not be awarded marks if you make a point and then for the second part write the opposite. For example, you might refer to deforestation increasing discharge and decreasing the lag time. If you then write about afforestation decreasing discharge and increasing the lag time, you will only be awarded 2 marks
Answer
More urbanisation (1) increases rates of run-off (or equivalent idea e.g. reduces infiltration) and/or more water in the river/higher discharge (1)
Changing agricultural practices/ land use (1) such as ploughing land previously left in grass which will increase runoff (1)
Deforestation/Afforestation (1) affects interception and infiltration rates so changing run-off and thus lag-times (1)
Climate change my increase/decrease storminess (1) which will affect lag-times because of changes in infiltration/run off relationships (1)
Human management of rivers e.g. levees (1) maintains more water in the channel (1)
Examiner Tips and Tricks
In 4 mark answers take care to not simply write the opposite for the second set of two marks. If you do this you are not showing the breadth of knowledge expected and will only be awarded marks for the first part of your answer. See the above worked example which illustrates where this could happen.
Case Study: River Ouse, York
York is a city located in the north of England
The city's population is just over 200,000
York regularly floods: Serious flooding has occurred in 1947, 1978, 1991, 1995, 2000 and 2015
The floods in 2000 were the worst on record
The Ouse rose almost 5.4 meters above its normal level
540 properties were flooded and 320 were at serious risk
18,700 hectares of farmland were affected
The overall cost of the floods was estimated to be over £12 million including lost income from tourism
Causes of 2015 flood
Physical and Human Causes of 2015 Flood
Physical Causes | Human Causes |
|---|---|
Before reaching York the Ouse is joined by a number of large tributaries (Swale, Ure and Nidd) which flow from the Yorkshire Dales | Farming in the Vale of York and grazing in the Yorkshire Dales means interception is reduced due to decreased tree cover and lack of other vegetation |
Annual precipitation levels in the Yorkshire Dales are between 600-1000mm. In 2010 one month's rain fell in just 24 hours | Increased urbanisation around the city with new housing developments, retail parks and industrial areas have increased impermeable surfaces |
Yorkshire Dales are upland areas with steep slopes | Erosion of peat in upland areas reduces the amount of moisture held in the soil |
Land around York is low-lying and flat | Failure of the Foss Barrier increased flooding in the east of the city |
York lies on the confluence of the rivers Foss and Ouse | Deforestation in upland areas |
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