4.8 Flashcards
How is global climate change increasing river flood risk?
As glaciers melts all the water will flow into the drainage basin and thermal expansion, from the heat, means that rivers levels will rise leading to higher chance of a flood happening and increase river levels a lot.
How is human activity in drainage basins increasing river flood risk?
As farmers increase and they can cut through other drainage basins and they think that they are doing a good job but they just made water from another drainage basin affect the other drainage basin so an increase is river levels.
Compare how soft and hard engineering schemes work.
Soft engineering works with nature and is more cheap but is less effective and not as permanent and could be expensive over time.
Hard engineering works against nature is more expensive but it is more effective and is mostly permanent and is a one time things half the time.
Explain what each hard engineering scheme is, how they work and the pros/cons
Flood walls
It is primarily vertical artificial barrier designed to temporarily contain the waters of a river.
Depends on the type of wall and material used. They disperse water quickly and can increase flood risk down stream.
These are fairly cheap and ‘one-off’ costs once a wall is built, it’s done.
Levees (embankments)
Are flood walls, building levees increases the capacity of the rivers and are normally built at distance from the river
Up to £1m depending on materials used
Expensive p, but allow people to live beside it.
Dredging and flood relief channel
Dredge the river to increase channel capacity or line it with concrete.
£50000 for a 1km channel in rather than cost £14m in 2008
Dredging needs to be done every year as the channel fills with sediment
Explain what each soft engineering is, how they work and the pros/cons.
Flood plain retention
The level of flood plain is lowered and their surfaces restored.
£1.2 million in total for a 2km stretch
Increased ability to store flood water
River channel restoration
Some meanders were rebuilt.
£1.2 million in total for a 2km stretch.
Improved ecology with a 30% increase in birds and insects within one year.
Afforestation
Planting trees in the upper course of the river intercepts large volumes of water and allows for more evapotranspiration. Surface run-off is reduced as a result and the flood risk is reduced.
Trees (if bought largely grown) are expensive, and if they are saplings (young) they take a long time before they are effective
