Lesson 8 - Physical Causes of Flooding

Question 1

What is surface water flooding?

Answer 1

Flooding that occurs when intense rainfall has insufficient time to infiltrate the soil, so flows overland. Common when the area has been urbanised and there are impermeable surfaces.

Question 2

Define the term groundwater flooding?

Answer 2

Flooding that occurs after the ground has become saturated from prolonged heavy rainfall.

Question 3

Define the term flash flooding?

Answer 3

A flood with an exceptionally short lag time - often minutes or hours.

Question 4

Define the term jokulhaup?

Answer 4

A type of glacial outburst flood that occurs when the dam containing a glacial lake fails.

Question 5

Explain how shallow soils can increase the risk of flooding?

Answer 5

Shallow soils means that less infiltration will take place and more surface runoff will occur. This means that there is an increased risk of flooding.

Question 6

How does the steepness of the slope impact the risk of flooding?

Answer 6

The steeper that the slope is, the greater the risk of flooding is. Steeper slopes means that there is less infiltration and more surface runoff. This means that there is a shorter lag time and therefore an increased risk of flooding.

Question 7

Explain how the rock type impacts the risk of flooding?

Answer 7

Impermeable rock increases the risk of flooding as there is less percolation and therefore more surface runoff. This means that the lag time is shorter, therefore increasing the risk of flooding.

Question 8

Explain why deforestation increases the risk of flooding?

Answer 8

The removal of trees via deforestation will reduce the amount of interception, therefore increasing the amount of surface runoff. This means that the lag time is lower and the risk of flooding is higher.

Question 9

State five physical causes of flooding?

Answer 9

• Prolonged heavy rainfall
• Seasonal monsoon rainfall
• Tense storms
• Snow and ice
• Local conditions