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16 Cards in this Set
- Front
- Back
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Why do floods happen?
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Rivers burst their banks onto the floodplain. Usually caused by heavy rainfall; the faster the rain reaches the channel, the nature of landscape influence how quickly the rainwater reaches the channel
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Steep sided valley
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River channel that has steep slopes cause fast surface run off
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Lack of vegetation and woodland
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Trees & plants catch water, if there is no vegetation in the drainage basin then the surface run off will be high
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Impermeable rock
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Water cannot percolate through the rock layer, it will run faster over the surface
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Drainage basin in an urban area
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Consist of impermeable concrete which encourages overland flow. Drains, sewers take water quickly to river channel & houses with sloping roofs increase amount of run off
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Management techniques
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1. River engineering
2. afforestation 3. planning controls to restrict urban development on floodplains |
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Impact of flooding
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1. Damage to homes & possessions
2. disruptions of communication 3. deposites alluvium - provides food |
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LEDC & MEDC
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LEDC's effected more because more farms, farming communities attracted to floodplains & don't have resources to prevent or deal with flooding
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Hard engineering
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More expensive & greater impact on river and surrounding landscape
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Soft engineering
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More ecologically sensitive & tables summarise main flood management techniques
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Types of hard engineering
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1. Dam construction
2. River engineering |
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Dam construction
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1.Built along course of river to control discharge. Water is held back & released in controlled way
2.Water held in reservoir behind dam. Used to generate hydroelectric power & recreation purposes 3.expensive 4.Sediment gets trapped turning to erosion 5.settlements & agricultural land may be lost when valley is flooded to form reservoir |
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River engineering
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1.River channel widened or deepened allowing more water. May be straightened so water travels faster.
2.May lead to greater risk of flooding downstream |
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Afforestation
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Trees planted near to river. Greater interception of rainwater & lower river discharge. Low cost which enhances quality of drainage basin
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Managed flooding
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Allowed to flood naturally to prevent flooding in other places
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Planning
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1.Authorities and government introduce policies to control town being built on floodplains. Reduces chance of flooding & risk to damage property
2.Resistance to development restrictions where shortage of housing, harder in LEDC's |
