Flooding (causes and management) *

Question 1

What are the three physical causes of flooding?

Answer 1

• precipitation (rain/snow/sleet etc.)
• geology (type and nature of rocks)
• relief (gradient of land)

Question 2

How does the amount of precipitation effect the likeliness to flood?

Answer 2

heavy rainfall means less water is soaked up by the soil (infiltration) so there is increased surface run-off
the faster the water reaches the river, the more likely it is to flood

Question 3

How does the duration of precipitation effect the likeliness to flood?

Answer 3

prolonged rainfall means that the soil becomes saturated until the water table reaches ground surface meaning that the ground is unable to absorb any more water
means there is an increased surface run-off -> the faster the water reaches the river, the more likely it is to flood

Question 4

How does snow melt effect the likeliness to flood?

Answer 4

when the temperature warms, the snow will melt
this can be a few days worth of precipitation and overwhelms river levels, resulting in flooding

Question 5

How does the permeability of rocks effect the likeliness to flood?

Answer 5

valleys made from impermeable rocks (do not allow water to pass through them) have a higher chance of flooding
this is because there will be decreased infiltration, therefore increased surface run-off
the faster the water reaches the river, the more likely it is to flood

Question 6

How do steep slopes effect the likeliness to flood?

Answer 6

steep slopes mean that water moves across land more quickly
this leads to decreased infiltration, therefore increased surface run-off
the increased volume of water reaching the river means it is more likely to flood

Question 7

How does low lying land effect the likeliness to flood?

Answer 7

low lying land is at risk of flooding as they don’t have enough gradient for water to move
this risk increases when the soil has a higher content of impermeable materials
this results in decreased infiltration and increased surface run-off

Question 8

What are the two human causes of flooding?

Answer 8

• urbanisation (development of towns and cities)
• deforestation (the cutting down of trees)

Question 9

How does urbanisation effect the likeliness to flood?

Answer 9

the growth of urbanisation has led to the increase of buildings and roads which are impermeable surfaces
this results in decreased infiltration and increased surface run-off

Question 10

How does deforestation effect the likeliness to flood?

Answer 10

cutting down trees increases the flood risk because trees intercept precipitation
trees also absorb water from the soil allowing greater infiltration
this means that eventually infiltration will decrease without trees, and surface run-off will increase

Question 11

What is soft engineering?

Answer 11

when the natural environment is used to reduce the risk of flooding

Question 12

What is hard engineering?

Answer 12

involves building artificial structures which try to control natural processes to help reduce the risk of flooding

Question 13

What are the four soft engineering strategies?

Answer 13

• flood plain zoning
• flood warnings and preparation
• planting trees
• river restoration

Question 14

What is flood plain zoning?

Answer 14

when land in a river valley is used to minimise the impact of flooding

Question 15

What are two pros and cons of flood plain zoning?

Answer 15

pros:
- low cost
- by restricting building on flood plains, impermeable surfaces don’t increase so the risk of flooding is reduced

cons:
- has limited impact as many UK cities have already built over active flood plains
- habitats are destroyed due to increased building in other areas

Question 16

What are two pros and cons of flood warnings and preparation?

Answer 16

pros:
- very cheap
- if people are warned in advance they can protect their valuables easier

cons:
- possible loss of agricultural land near rivers
- not always the most effective or practical strategy

Question 17

What are two pros and cons of planting trees?

Answer 17

pros:
- reduces amount of water flowing downstream as shelter belts of trees can reduce surface run-off
- more CO2 absorbed

cons:
- changed appearance to countryside
- loss of potential grazing land

Question 18

What are two pros and cons of river restoration?

Answer 18

pros:
- creates new wetland habitats which increases biodiversity
- increased water storage areas reduce the risk of flooding downstream

cons:
- possible loss of agricultural land
- can be expensive

Question 19

What are the three hard engineering strategies?

Answer 19

• dams and reservoirs
• embankments
• flood relief channels

Question 20

What are two pros and cons of dams and reservoirs?

Answer 20

pros:
- boosts tourism
- promotes new habitats which develop around dams and reservoirs

cons:
- expensive
- soils downstream can become less fertile through lack of sediment from floods

Question 21

What are embankments?

Answer 21

artificially raised river banks

Question 22

What are two pros and cons of embankments?

Answer 22

pros:
- safer from flooding , the channel has an increased carrying capacity
- cheap

cons:
- higher maintenance costs, needs constant monitoring and repair
- stops people from having easy access to the river for fishing etc

Question 23

What are two pros and cons of flood relief channels?

Answer 23

pros:
- removes the risk of flooding from a designated area
- can provide new habitats

cons:
- people living in the path of a relief channel have to be moved
- expensive