Flooding & Climate Change

Flooding & it's impacts

Multiple Choice

What is a flood?

• When too much water falls from the sky

• When lots of water reaches the land

• When a river bursts its banks

• When a river meets the sea

Multiple Choice

A cause of flooding is when more rain falls than the river channel can hold and water flows over the banks onto the flood plain.

• true

• false

Flooding

Flooding happens when more rain falls on an area that the river can cope with. The river will burst it's banks and the floodplain will be covered with water.

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​Flash floods usually happen after sudden heavy rainfall. There is a delay between peak rainfall and peak river discharge as the water has to travel to the river.

Vocabulary recap​

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Water Cycle

Multiple Choice

Water that falls from the sky is called...

• Condensation

• Precipitation

• Infiltration

• Interception

Vocabulary

Precipitation - water falling from the skay as rain, snow, sleet or hail.

Infiltration - water slowly moving into the soil and moving below ground towards a river or the sea.

Run-off - water moving accross the surface of the land into a river or the sea.

Interception - precipitation that does not directly hit the ground due to tress and plants intercepting the flow.​

Multiple Choice

Runoff is...

• water falling from the atmosphere as rain, hail, sleet or snow

• rainwater soaking into the ground

• evaporation of water from leaves

• rainwater moving over the ground surface

Multiple Choice

Trees and plants acting as an umbrella to stop rain hitting the ground is called...

• infiltration

• interception

• runoff

• impermeable

Multiple Choice

Infiltration is...

• water flowing down a road

• water flowing onto a flood plain

• water sinking into the soil

• where a river meets the sea

Humans and flooding

When trees are removed from the environment this increases the risk of flooding. There is less interception so precipitation falls directly onto the ground.

If natural areas are replaced with roads and buildings, the risk of flooding also increases as there is less infiltration and more run-off. Run-off is a more direct ​route and happens faster.

Multiple Choice

What pairs of factors are human causes of flooding?

• Heavy rainfall & urbanisation

• Steep slopes & deforestation

• Urbanisation & deforestation

• Snow melt & urbanisation

Multiple Choice

Which one of these will reduce the risk of flooding?

• cutting down trees

• building more roads

• planting trees

• building more houses

Flooding & Climate Change

By Lucy Brown

Extreme weather

As we discussed yesterday, climate change is leading to more extreme weather events.

This in turn can lead to more flooding as storms and precipitation are more powerful and more water is moved around the planet.​

Case Study - China

Flooding in China

​Sourced from BBC News

Many parts of eastern China experienced severe flooding in June and July in 2020.

​The Yangtze river saw the heaviest rainfall since 1961, with a 79% increase in June and July compared to the average for the period over the previous 41 years.

​Several dams across the country's largest fresh water lake, Poyang, burst.

​33 rivers had reached record highs.

​140 people are reported to have died and millions were evacuated.

July 2020

Open Ended

Why is it significant that dams have burst? What would be the impact of this?

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What happened?

Scientists say that a rapid drop in emissions because of Covid played a key role in record rainfall in China in 2020.

The decline in greenhouse gases and small particles called aerosols caused atmospheric changes that intensified the downpours.

" In a new study, authors show that over the past four decades summer rainfall over eastern and central China has decreased significantly due to the increase in the number of aerosols in the atmosphere. These particles, often associated with the burning of coal, can reduce the occurrence of large-scale storms which resulted in lower rainfall." 

Prof Yang Yang from Nanjing University

"There was heating over land due to aerosol reductions but also cooling over the ocean due to a decrease in greenhouse gases, which intensified the land/sea temperature difference in the summer,"

"This in turn, increased sea level pressure over the South China/Philippines sea and intensified the winds bringing moist air to eastern China which then saw intense precipitation."