Flooding - Paper 1

Question 1

What are the 7 stages going downwards on the left hand side of the drainage basin hydrological cycle?

Answer 1

-Precipitation
-Interception
-Surface storage
-Infiltration
-Soil moisture
-Percolation
-Groundwater.

Question 2

What does interception of precipitation lead to?

Answer 2

Evaporation and transpiration.

Question 3

What is infiltration?

Answer 3

Water sinking into soil/rock from the ground surface.

Question 4

What is percolation?

Answer 4

Water seeping deeper below the surface.

Question 5

What is groundwater?

Answer 5

Water stored in the rock.

Question 6

What does surface storage lead to?

Answer 6

Surface run-off (overland flow)

Question 7

What does soil moisture lead to?

Answer 7

Throughflow.

Question 8

What does groundwater lead to?

Answer 8

Groundwater flow.

Question 9

What 2 things does surface runoff lead to?

Answer 9

-Evaporation
-River carrying water to a lake or sea.

Question 10

What 4 physical factors increase flood risk?

Answer 10

-Depressions passing over the UK at frequent intervals
-Sudden bursts of heavy rain
-Prolonged light rainfall
-Sudden snow melt.

Question 11

How can bands of depression passing over the UK at frequent intervals increase flood risk?

Answer 11

It results in continuous heavy rainfall which may saturate the soil, meaning the soil can no longer store water so surface runoff is increased. Rainwater will therefore enter the river quicker resulting in high discharge and floods.

Question 12

How can sudden bursts of heavy rainfall increase flood risk?

Answer 12

They often result in the infiltration rate being too slow to cope. This may occur after a period of drought that has baked the soil hard. Surface run off occurs, discharge increases quickly and flash floods occur.

Question 13

How can prolonged light rainfall increase flood risk?

Answer 13

If there has been a lot of previous rainfall which has saturated the soil.

Question 14

How can sudden snow melt increase flood risk?

Answer 14

It causes a release of stored water that flows over the ground as surface runoff.

Question 15

Where are 2 places that geology can increase flood risk there and why?

Answer 15

-The type of rock found in mountains is usually impermeable such as slate, which does not allow water through it. The rock is often bare with thin soils and little vegetation to intercept rain.

-Low-lying areas often contain an impermeable clay soil. It’s usually vegetated, but the soil is so compacted that is it difficult for infiltration to occur.

Question 16

Where is flooding much less likely because of its geology and why?

Answer 16

In areas of permeable rock such as chalk or limestones, as water passes through these rocks.

Question 17

How does relief in mountain sides increase flood risk there?

Answer 17

Steep slopes means that surface runoff occurs on mountain sides before rain has had time to infiltrate the soils. Therefore a valley floor with steep sides has a high flood risk.

Question 18

How does relief of floodplains increase flood risk there?

Answer 18

Low-lying, flat floodplains do not have a big enough gradient to remove the water. The flood risk is increased further by impermeable clay soils

Question 19

What is relief rainfall?

Answer 19

When high relief causes on-shore winds to rise, and as the air rises it cools and condenses to form rain.

Question 20

What are the 6 human causes of flooding?

Answer 20

-New infrastructure
-New houses
-Disappearing gardens
-Forestry
-Farming
-Disappearing fields.

Question 21

How does new infrastructure increase flood risk?

Answer 21

Urbanisation leads to growth of towns and cities. Population growth means new roads, shopping centres, school, leisure centres etc are built. The greater the area covered by buildings and roads (with impermeable surfaces), the greater the potential flood risk.

Question 22

How do new houses increase flood risk?

Answer 22

With increased demand for houses in the UK, thousands of new homes are built each year, many on greenfield sites. Large areas of flood plain are now covered with impermeable tarmac roads and concrete pavements. Cities therefore have few natural areas in which to store excess water. Water runs quickly through gutters, drains and culverts and this leads to a speedy rise in river’s discharge - hence the increased flood risk.

Question 23

How does disappearing gardens increase flood risk?

Answer 23

The growth of impermeable surfaces is becoming worse in our larger cities, where people pave over gardens to save mowing the lawn or to accommodate their cars with an absence of a garage and little ‘on road’ parking.

Question 24

How does forestry increase flood risk in 2 ways?

Answer 24

-Reduces interception and roots no longer take water from the soil. After felling, the soil soon gets saturated, runoff occurs, river discharge increases quickly and so does the risk of flooding.

-Also causes exposed soil to wash into the rivers, building up their beds. This reduces the capacity of channels, so rivers are more likely to flood.

Question 25

How does farming increase flood risk in 3 ways?

Answer 25

-Since WW1 hedges have been pulled out to make way for huge fields that are more efficient for high mechanised arable farming. Loss of hedges means less interception.

-Farming has become more intensive. Once crops have been harvested, they leave the soil bare in winter. this means there is no vegetation to intercept rainfall.

-When fields are ploughed up and downhill, furrows create channels for water to flow down easily. More soil is transported into the rivers, raising their beds and so increasing flood risk.

Question 26

What are 5 reasons of fields disappearing which increase flood risk?

Answer 26

-Fields intercept rain and soak up excess water through infiltration.
-Some fields may be sold to developers, while others may be converted to riding stables
-As large-scale factory farming increases , fields have also been replaced by huge sheds and concrete yards
-Pastures have been over grazed
-To extend the growing season of fruit and vegetables, vast areas of polythene cover fields of crops.

Question 27

Between 2001 and 2011, there was in increase in how much in the average density of new dwellings in England?

Answer 27

72%

Property developers are squeezing several houses into a plot formerly occupied by only one house.

Question 28

How can rural land increase flood risk?

Answer 28

Changing land use and farming practises can increase flood risk.

Question 29

How much precipitation would a dense forest use up and what does this mean?

Answer 29

Impact of felling is considerable as a dense forest uses up 40% of precipitation.

Question 30

What is the result of pastures being over-grazed?

Answer 30

This has compacted soil and degraded pastures, resulting in muddy runoff into rivers and increased risk of flooding

Question 31

How does covering areas of field with polythene (to extend growing season) increase flood risk?

Answer 31

Although there may be some interception and evaporation from the poly tunnels, the ability of the area to soak up water is reduced.

Question 32

A river’s discharge can depend on what 3 factors about precipitation?

Answer 32

Amount, type and intensity.