EQ5: 4.8 Flashcards
Why is river flood risk increasing? Include global climate change and
human activity in drainage basins
More trees are being cut down for human use and this increases surface run off which increases the risk of flooding. There is more flood risk because there is more and more rainfall occurring. Dredging speeds up river flow which increases the risk of flooding downstream.
Compare how soft and hard engineering schemes work
Hard engineering is made to reduce the risk of flooding long term and to be very effective. Soft engineering is made to reduce the risk of flooding but it wont be as long term and not as effective.
Explain what each hard engineering scheme is, how they work and the
pros/cons
Flood walls- build a high wall alongside a river to increase its capacity to prevent flooding. Pros= useful for city centres where space is limited. “One off costs”. Cons= they disperse water quickly and can increase the flood risk downstream.
Levees- building levees increases the capacity of the river and are normally built at a distance from the river. Pros= allow people to live beside rivers of farm with reduced fear of flooding. Cons= can increase flooding downstream. Can over-topple.
Dredging and flood relief channel- dredging increases channel capacity, or line it with concrete to speed up river flow. FRC creates extra channels to divert excess water from city centre. Pros= concrete lining is cheap to maintain. Protects built up areas. Cons= dredging needs to be done every year as the channel fills with sediment. Increases flood risk downstream.
Explain what each soft engineering scheme is, how they work and the
pros/cons
Flood plain retention- level of flood plains lowered and their surfaces restored to shrubs or grassland, so they retain water over a period. Pros= increased ability to store floodwater. Cons= £1.2 million in total for a 2km stretch.
River channel restoration- some meanders were rebuilt, lengthening the river and slowing water down. Banks lowered to make river flood parks instead of towns. Concrete and other hard materials stripped away, replaced with sediment. Pros= improved ecology with a 30% increase in birds and insects, within 1 year. People like more natural look. Cons= £1.2 million in total for a 2km stretch.
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. Pros= natural way of reducing flood risk which improves the view in an area. Increases natural habitats for wildlife too. Low maintenance required.
