river engineering Flashcards

1
Q

hard engineering

A

manmade structure put next to a river to prevent flooding

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2
Q

soft engineering

A

the use of sustainable or ecological methods to prevent flooding

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3
Q

What do the C,B,A stand for in the CBA structure used for compare river engineering methods

A

Cost
Benefit
Analysis

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4
Q
  1. how do dams work?

2. CBA for dams

A
  1. Build a wall across a river to control river flow, storing water above the dam in a reservoir to prevent flooding downstream
  2. very expensive
    water in reservoirs can be used as drinking water
    reservoirs store water reducing risk of flooding
    effective at preventing floods
    generate hydroelectric power

But environmental damage, massive impact on local ecosystems and dams could still flood
eroded material is deposited in reservoir and will build up over time reducing carrying capacity

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5
Q
  1. how do embankments work

2. CBA for embankments

A
  1. building walls alongside river banks to prevent flooding when the river levels get too high
    2.it is medium cost
    stops a lot of flooding

but due to extreme weather because of climate change this may not be enough
impact on wildlife as you are modifying the environment

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6
Q
  1. how does channel straightening work

2. CBA for channel straightening

A
  1. straightening the channel (cutting off the meanders artificially) means more water is moved more quickly away from urban areas so pushing flood water downstream
  2. isn’t too expensive in comparison to a dam
    moves water outer of the area quicker so reduces the risk of flooding

but
moving the problem further downstream
more erosion downstream because the water is flowing faster

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7
Q
  1. how does a flood relief channel work

2. CBA for flood relief channel

A
  1. creating a new channel next to the river to direct water away from urban areas. Can also allow extra river capacity to reduce flooding
  2. medium cost
    takes water away from houses preventing expensive damage to property
    but will it be enough climate change more rain more freak weather
    more concrete is just increasing surface runoff and reducing infiltration
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8
Q
  1. how does river restoration work

2. CBA for river restoration

A
  1. returning the river to its natural state, where it is allowed to flood in certain areas or creating wetlands to catch/ slow down flood water naturally
  2. it is very cheap
    more infiltration as there won’t be as many impermeable surfaces
    better for local ecosystems
    less risk of flooding downstream because discharge is reduced
    but
    the environment may never go back to the way it was again
    ruined the soil structure
    level of biodiversity may not ever be reached again
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9
Q
  1. how does flood plain zoning work

2. CBA for flood plain zoning

A
  1. more expensive land use is moved further away to reduce damage and costs of flooding
  2. prevents damage to people’s lives
    risk of flooding is reduced
    impermeable surfaces aren’t created
    impact of flooding is reduced as there is no buildings to damage
    but
    contradicts warning system as why would you have a warning system if no one lives nearby
    expansion of urban areas is limited if there are no other suitable building sites
    doesn’t help in areas that are already at risk of flooding and have been built on
    doesn’t take the local wildlife in an ecosystem into consideration
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10
Q
  1. how does a warning system work

2. CBA for warning systems

A
  1. warning of floods so people can evacuate through tv, radio, newspapers, internet
  2. reduces impact of flooding (gives people time to move possessions, place sandbags, evacuate)
    prevents death as people can be warned then evacuate
    but isn’t doing anything to stop the river flooding and preventing damage to the environment or houses
    people may not hear or have access to the warnings
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11
Q
  1. how does afforestation work

2. CBA for afforestation

A
  1. planting trees in the river valley increases interception and lag time so reduces the risk of flash flooding
  2. not too expensive, no carbon dioxide emissions
    flood risk and river discharge are reduced and vegetation reduces soil erosion in the valley and provides habitats for wildlife
    but this means there is less land for farming which is a problem with a growing population and trees take a long time to grow
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