Now that you have completed this study session, you can assess how well you have achieved its Learning Outcomes by answering these questions.

Explain how each of the human activities described in (1) and (2) can increase the risk of flooding:

  • (1) constructing roads and urban areas on land previously used for agriculture
  • (2) deforestation.

Explain how each of the human activities described in (3) and (4) can increase the risk of droughts:

  • (3) population pressure
  • (4) deforestation

Show answer

  1. Urbanisation increases the risk of flooding because the paved surfaces and concrete constructions are impermeable and prevent rainfall from soaking into the soil as it used to do when the land was used for agriculture.
  2. Deforestation increases soil erosion because bare soil is more easily washed away by heavy rain when not held together by tree roots. Soil washed off the land builds up in reservoirs and rivers, significantly reducing their water-holding capacity, so they overflow during intense rainfall and flood surrounding areas.
  3. Population pressure increases the risk of droughts because there is increasing demand for water as the population increases, especially when concentrated in urban areas, where water is required for additional uses in industry and to meet rising expectations of piped water and sanitation.
  4. Deforestation increases the risk of droughts because forests reduce the loss of rainwater through evaporation from the surface of bare soil, they increase groundwater storage by reducing run-off, and they add moisture to the atmosphere through transpiration.

Explain how each of the extreme weather events listed in (1) to (3) can affect water quality :

  1. floods
  2. droughts
  3. wildfires.

Show answer

  1. Floods affect water quality by washing animal, human, agricultural and industrial waste into streams, rivers, lakes and reservoirs, contaminating the water with infectious organisms, chemicals and other toxins so it is unsafe for domestic use.
  2. Droughts affect water quality by concentrating contaminants such as infectious organisms, chemicals and other toxins in environmental water sources as they shrink due to evaporation.
  3. Wildfires affect water quality because burning vegetation generates smoke, debris, ash and toxic chemicals, which are washed by rain into water sources.

Last modified: Monday, 3 October 2016, 7:27 AM