Flood

Question 1

What is a flood?

Answer 1

When water overflows its bank and spreads out onto the surrounding land

Question 2

Why are the physical causes of flood?

Answer 2

Heavy rainfall
Climate
Snowmelt
Steep sided channel 
Impermeable rocks(doesn’t allow water through)
Vegetation

Question 3

What are the human causes of flooding?

Answer 3

Urbanization - towns and cities have more impermeable surfaces

Deforestation - removing tress reduce the amount of water intercepted and increases run-off(when rainwater flows over the surface of land)

Question 4

What is river discharge?

Answer 4

The volume of water flowing through a river channel

Question 5

What is river surface run-off?

Answer 5

Water flows over the land surface

Question 6

What is a steep sided channel

Answer 6

A river channel surrounded by steep slopes

Question 7

What is a storm hydrograph?

Answer 7

A graph to show how and when a rainfall event affects the discharge of a river

Question 8

What is lag time?

Answer 8

Time taken between peak rainfall and peak discharge

Question 9

What is rising limb?

Answer 9

Increase in discharge on a hydrograph

Question 10

What is base flow?

Answer 10

The normal discharge of a river

Question 11

What is peak discharge?

Answer 11

Maximum amount of water held in the channel

Question 12

What is peak rainfall?

Answer 12

Maximum amount of rainfall

Question 13

What is falling limb?

Answer 13

Return of discharge to base flow

Question 14

What are the factors that for influence lag time?

Answer 14

Size of drainage basin
Vegetation
Valley side steepness
Soil type

Question 15

What unit is river discharge measures in?

Answer 15

Cumecs

Question 16

How do steep valley sides affect the flood hydrography?

Answer 16

They increase the peak discharge

Question 17

how are people in MEDCs and LEDCs affected differently by flooding?

Answer 17

People in LEDCs cannot afford home insurance so they lose everything

Question 18

How is climate a cause of flooding?

Answer 18

If the climate of an area has high temperatures, this will mean more water is lost through evaporation, resulting in less overland flow and less water reaching to the river, causing a lower river discharge. And the warmer air will hold more rainwater, making rainfall more likely.

Question 19

how is a steep sided channel a cause of flooding?

Answer 19

A river channel, surrounded by steep slopes, causes fast surface run-off.

Question 20

How is vegetation decrease flooding?

Answer 20

The more vegetation there is in an area, the greater the amount of rainfall that is captured and the less water there is available to flow over the surface

Question 21

How is impermeable rock a cause of flooding?

Answer 21

if a drainage basin consists too many impermeable rocks, this means that water cannnot pass through the rock layer so it will run faster over the surface.

Question 22

how is geology affects flooding?

Answer 22

The geology(rock type) influences the speed and quantity of water that reaches a river. Rocks that are permeable allow water into them (this is called percolation) and slowly flow through them, meaning less water gets to the river and at a slower rate, reducing the discharge of a river.

Rocks that are impermeable do not allow water into them, so they cause a faster run off. As a result, rainwater gets to the river quicker, causing the discharge of the river to be higher.

Question 23

What are the types of impermeable surfaces found in urbanised areas?

Answer 23

Roof tops, pavements, roads, street

Question 24

Why does a greater amount of rainwater get to the river channel in an urbanised area?

Answer 24

Because there is more impermeable surfaces built everywhere, decreasing the chances of infiltration and percolation and more over-land flow reaching the river channel quickly

Question 25

How is deforestation a cause of flooding?

Answer 25

Because if there is less vegetation, roots and plants, they will not be able to absorb the water reducing interception. Therefore, this increases the chances of over land flow and with less water taken up by the trees, a greater volume of water reaches the river, causing a greater discharge.