river engineering

Question 1

hard engineering

Answer 1

manmade structure put next to a river to prevent flooding

Question 2

soft engineering

Answer 2

the use of sustainable or ecological methods to prevent flooding

Question 3

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

Answer 3

Cost
Benefit
Analysis

Question 4

1. how do dams work?

2. CBA for dams

Answer 4

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

Question 5

1. how do embankments work

2. CBA for embankments

Answer 5

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

Question 6

1. how does channel straightening work

2. CBA for channel straightening

Answer 6

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

Question 7

1. how does a flood relief channel work

2. CBA for flood relief channel

Answer 7

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

Question 8

1. how does river restoration work

2. CBA for river restoration

Answer 8

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

Question 9

1. how does flood plain zoning work

2. CBA for flood plain zoning

Answer 9

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

Question 10

1. how does a warning system work

2. CBA for warning systems

Answer 10

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

Question 11

1. how does afforestation work

2. CBA for afforestation

Answer 11

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