Physical And Human Cause Off Flooding

Question 1

Summarise physical causes of flooding

Answer 1

Steep sided channel causes fast surface run off
Lack of vegetation - more surface run off
Drainage basin formed of impermeable rock- water cannot percolate through the rock.
Heavy rainfall- saturated soil
Long periods of rainfall - saturated soil
Snowmelt - particularly when soil is frozen because infiltration capacity is decreased.
Compacted or bone dry soil
Climatic hazards such as cyclones.

Question 2

Human causes of flooding (summarise)

Answer 2

Urbanisation
Deforestation
River management
Climate change

Question 3

How does urbanisation contribute to flooding?

Answer 3

• More people living in towns and cities.
• Population growth and urbanisation has led to demand for land to build on - floodplains are flat and are used for housing.
• concrete and Tarmac, used for roads and pavements, are impermeable. Precipitation cannot infiltrate.
• less interception as vegetation is removed so precipitation gets into the river more quickly.
• bridges over rivers can constrict rivers, slow discharge and reduce the carrying capacity of the river.

Question 4

How does deforestation contribute to flooding?

Answer 4

• No vegetation, there is greater risk of soil erosion as the precipitation is not intercepted.
• flood damage is greatest near the mouth of a river because wide, flat floodplains are most susceptible to damage. The volume of water is greatest here because many tributaries have joined the river.

Question 5

How does river management contribute to flooding?

Answer 5

Main aim of river management is to reduce the likelihood of flooding. However, in some circumstances it can actually increase the risk: Bangladesh: flood embankments have built along some river channels. They are designed to increase river capacity but at times prevented floodwater draining back into rivers.

Question 6

How does climate change contribute to flooding?

Answer 6

• global warming blamed for increasing frequency of flooding.
• average sea temperature have raised and this rise has been blamed for the increasing frequency and severity of tropical revolving storms in the Caribbean because such storm bring heavy rainfall and storm surges along the coastlines of some countries.
• higher temp- greater precipitation- more flooding, especially since floodplains have become highly urbanised over last two centuries.
• global warming has also been linked to an increased frequency of El Niño events. El Niño is caused by reversal in ocean currents in the Pacific Ocean. Normally cold current encourage high pressure condition, in El Niño low pressure weather dominates in increased rainfall and flooding to west coast of America.
• global warming- lead to melting ice caps- rise in sea level - food plains lying close to present sea levels would be at risk of flooding.