Storm hydrographs and River Discharge

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  • Created by: Helena26
  • Created on: 02-02-13 19:56
What are storm hydrographs?
Storm hydrographs are graphs that show how a drainage basin responds to a period of rainfall.
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Why are storm hydrographs useful?
They are useful in planning for flood situations and times of drought as they show the discharge (amount of water reaching channel via surface run-off, throughflow, and base flow) that originated as precipitation.
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What influences how quickly or slowly river discharge increases after a storm?
Drainage basins all have a variety of characteristics in terms of vegetation, geology, soil type and so on, all of which interact to influence how quickly or slowly river discharge increases after a storm.
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How does the size of basin influence hydrographs and drainage basins?
Size - the smaller the basin the less time it takes for water to drain to the river, resulting in a shorter lag time.
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How does the shape of basin influence hydrographs and drainage basins?
Shape - the shape of basin that lends itself to most rapid drainage is circular. In a long, narrow basin water takes longer to reach the river.
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How does the relief of basin influence hydrographs and drainage basins?
Relief - the steeper the basin the more quickly it drains.
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How does heavy storms (precipitation) influence hydrographs and drainage basins?
Heavy Storms - in such a situation, rainfall is often far in excess of the infiltration capacity of the soil leading to much overland flow, and rapid rises in river levels.
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How does lengthy rainfall (precipitation) influence hydrographs and drainage basins?
Lengthy rainfall - leads to the ground being saturated and overland flow.
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How does snowfall (precipitation) influence hydrographs and drainage basins?
Snowfall - until snow melts, potential discharge for a river is held in storage. Rapid melting can lead to flooding.
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How does temperature influence hydrographs and drainage basins?
High rates of evapotranspiration reduce amounts of discharge, and low temperatures can store water in the form of ice and snow.
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How does land use influence hydrographs and drainage basins?
Important in reducing discharge as it intercepts precipitation and adds to rates of evapotranspiration. Roots of plants take up water reducing throughflow. Interception is less in winter in the UK due the shedding of leaves from deciduous trees.
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What varies within drainage basins?
Rock types.
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Rock types can be what?
Can be permeable (allowing water through) or impermeable (not allowing water through).
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Permeable rocks can be what?
Permeable rocks can be porous such as chalk that store water within them or pervious, such as limestone where water flows along bedding plains.
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Impermeable rocks can be what?
Impermeable rocks encourage grater amounts of surface run-off and a more rapid increase in discharge than permeable rocks.
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How does soil influence hydrographs and drainage basins?
A control on the rate of infiltration, amount of soil moisture storage and rate of throughflow. Larger pore spaces as found in sand, allow for greater water storage and limit the risk of flooding.
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How does drainage density influence hydrographs and drainage basins?
As stated earlier, the higher the density the greater the risk of flooding.
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How does tides and storms influence hydrographs and drainage basins?
High spring tides (illustrated by the Severn Bore) prevent water from entering the sea and increase the risk of flooding.
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How does urbanisation influence hydrographs and drainage basins?
A major impact because of its alteration on the hydrological process.
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Other cards in this set

Card 2

Front

Why are storm hydrographs useful?

Back

They are useful in planning for flood situations and times of drought as they show the discharge (amount of water reaching channel via surface run-off, throughflow, and base flow) that originated as precipitation.

Card 3

Front

What influences how quickly or slowly river discharge increases after a storm?

Back

Preview of the front of card 3

Card 4

Front

How does the size of basin influence hydrographs and drainage basins?

Back

Preview of the front of card 4

Card 5

Front

How does the shape of basin influence hydrographs and drainage basins?

Back

Preview of the front of card 5
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