Floods
Floods are a naturally occurring event that have an integral part in many ecosystems but with many natural flood plains or drainage systems being turned into farmland and many areas being built up into cities, floods can’t take their natural course and as a result, they can often cause massive devastation to communities and infrastructure.
What causes floods?
Floods are usually caused by heavy rains but this alone is not enough to cause flooding because water naturally has ways to flow away. Naturally, water would flow through rivers, disperse over flood plains, or seep into the ground but if natural watercourses have been altered by humans, or if ground is already water-logged, the water will have nowhere to go and as a result, the area will flood.
In coastal areas, flooding could also have a number of other causes including cyclones, tsunamis, extreme high tides, or dam failures; which could also happen inland.
In coastal areas, flooding could also have a number of other causes including cyclones, tsunamis, extreme high tides, or dam failures; which could also happen inland.
Floods are usually caused by heavy rains but this alone is not enough to cause flooding because water naturally has ways to flow away. Naturally, water would flow through rivers, disperse over flood plains, or seep into the ground but if natural watercourses have been altered by humans, or if ground is already water-logged, the water will have nowhere to go and as a result, the area will flood.
In coastal areas, flooding could also have a number of other causes including cyclones, tsunamis, extreme high tides, or dam failures; which could also happen inland.
In coastal areas, flooding could also have a number of other causes including cyclones, tsunamis, extreme high tides, or dam failures; which could also happen inland.
How common are floods?
In comparison to other natural disasters, floods are a relatively common event in Australia and with an average of over 1.5 major floods per year (7) They are the second most common extreme weather event to occur in Australia, outnumbered only by cyclones, and there have been over 50 recorded floods just since 1980.
What are the different types of floods?
There are three main types of floods: Slow onset floods, rapid onset floods, and flash floods (8).
Slow onset floods are slow to start and usually occur in the more inland areas of Australia, west of the Great Dividing Range when river levels slowly rise until they break their banks and the water slowly spreads over large flood plains. They can last for long periods of time and can often cause whole communities to be isolated (8).
Rapid onset floods usually occur in mountain or coastal areas because most rivers in these areas are steeper and flow faster. As a result of the higher strength and speed of the water flows, rapid onset floods can cause greater damage to property but they only last for a couple of days at the most (8).
The third major type of floods are flash floods which are usually in low lying areas and are caused by sudden bursts of extreme rain or storms. They don’t last long but they are much more powerful than other types of floods and as a result, they can cause more damage (8).
Slow onset floods are slow to start and usually occur in the more inland areas of Australia, west of the Great Dividing Range when river levels slowly rise until they break their banks and the water slowly spreads over large flood plains. They can last for long periods of time and can often cause whole communities to be isolated (8).
Rapid onset floods usually occur in mountain or coastal areas because most rivers in these areas are steeper and flow faster. As a result of the higher strength and speed of the water flows, rapid onset floods can cause greater damage to property but they only last for a couple of days at the most (8).
The third major type of floods are flash floods which are usually in low lying areas and are caused by sudden bursts of extreme rain or storms. They don’t last long but they are much more powerful than other types of floods and as a result, they can cause more damage (8).
Where are floods most likely to happen?
Because floods can have so many different causes, they can occur almost anywhere but most floods occur in coastal areas and almost none occur in the dry, arid centre of Australia. The reason for this is that floods are usually caused by heavy rain and in Australia’s deserts, there isn’t much moisture in the air that could possibly cause rains heavy enough to bring floods, while in coastal areas, water is evaporated from the ocean in large enough amounts so rain is much more common.
When are floods most likely to occur?
In the north of Australia, there is a very high chance of flooding during summer while that risk is almost non-existent during winter (3), however in other regions such as the southern most parts of Western Australia and the area around Adelaide, there is a Mediterranean climate which means they have lots of rain in winter and not much rain in summer (9). The occurrence of floods are also highly affected by the Pacific Ocean, meaning that during El Niño years, Australia’s east coast will experience dryer conditions while La Niña years will cause significantly higher moisture and therefore a heightened risk of floods (10).
What impacts do floods have?
Floods have massive impacts but these can be summed up as impacts on the environment, the economy, and society.
Since floods are a natural phenomenon and have been happening for millions of years, many plants and animals have adapted to them and as a result, some ecosystems rely on floods to survive such as Lake Eyre or Barmah–Millewa Forest. Plants are mostly benefitted because floods help to spread nutrients over flood plains that may otherwise have been very barren while many species of animals can only breed or have their eggs hatch during floods.
Floods can also help to clean out many natural watercourses by removing algae or salt but they can also have very negative effects on the environment in various ways. These include causing contamination of drinking water or natural watercourses, destroying and killing plants and animals, and they can also cause immense amounts of erosion, destroying landscapes and uprooting trees and other plants.
Another area that floods have an affect on is the economy. They can do damage to farms by waterlogging crops and killing animals, and could also cause large-scale destruction of houses and infrastructure. It cost the Australian economy about 10 billion dollars to recover from the 2010-11 Queensland floods and that is just one event (12).
The final major area that floods have an impact on is society. Despite the obvious problems that floods cause to people’s houses and property, as well as the other infrastructure that people rely on to live their lives, floods also impact society through loss of life and the increased risk of outbreaks of water borne diseases.
Since floods are a natural phenomenon and have been happening for millions of years, many plants and animals have adapted to them and as a result, some ecosystems rely on floods to survive such as Lake Eyre or Barmah–Millewa Forest. Plants are mostly benefitted because floods help to spread nutrients over flood plains that may otherwise have been very barren while many species of animals can only breed or have their eggs hatch during floods.
Floods can also help to clean out many natural watercourses by removing algae or salt but they can also have very negative effects on the environment in various ways. These include causing contamination of drinking water or natural watercourses, destroying and killing plants and animals, and they can also cause immense amounts of erosion, destroying landscapes and uprooting trees and other plants.
Another area that floods have an affect on is the economy. They can do damage to farms by waterlogging crops and killing animals, and could also cause large-scale destruction of houses and infrastructure. It cost the Australian economy about 10 billion dollars to recover from the 2010-11 Queensland floods and that is just one event (12).
The final major area that floods have an impact on is society. Despite the obvious problems that floods cause to people’s houses and property, as well as the other infrastructure that people rely on to live their lives, floods also impact society through loss of life and the increased risk of outbreaks of water borne diseases.