Summary

In this Study Session, you have learned that:

• Extreme weather is weather that departs from the normal range of climate conditions.
• Floods, droughts, heatwaves and wildfires are common extreme weather events.
• Flash floods develop rapidly and are due to the run-off of intense rainfall collecting in a localised area, usually for a short time. River floods occur when the water level rises and spills over the river banks; the build-up is generally slower than in a flash flood, but the extent is greater and the duration is longer.
• Floods cause major damage to basic facilities such as water supplies, sanitation and waste disposal systems; they contaminate water sources by flushing pathogens, soil and toxins into rivers, lakes, ponds and wells.
• Drought is the absence of rain for extended periods, often for a season or more. The frequency of droughts has increased over time in many parts of the earth.
• There are many contributing factors to floods and droughts, including population pressure, deforestation, climate change and the occurrence of natural climate cycles due to El Niño and La Niña currents in the Pacific Ocean.
• Drought has a significant effect on water resources and WASH; it causes water scarcity which in turn may lead people to use unsafe water sources.
• A heatwave occurs when the daily maximum temperature on more than five consecutive days exceeds the average maximum temperature by 5 °C.
• Climate change is expected to increase the intensity and frequency of drought in many parts of the earth, in turn causing more severe and frequent heatwaves and wildfires.
• When debris and ash from the wildfires enter the atmosphere, they can cause respiratory problems; when they are washed into water sources by rain they can significantly reduce water quality.