Why do floods occur?

The Australian Government introduced a standard definition of flood for certain insurance policies. For this purpose, a flood is defined as:

The covering of normally dry land by water that has escaped or been released from the normal confines of: any lake, or any river, creek or other natural watercourse, whether or not altered or modified; or any reservoir, canal, or dam.

Floods can bring welcome relief for people and ecosystems suffering from prolonged drought, but also are estimated to be the most costly natural disaster in Australia.

Why do floods occur?

Flooding occurs most commonly from heavy rainfall when natural watercourses do not have the capacity to carry excess water. However, floods are not always caused by heavy rainfall. In coastal areas, water inundation can be caused by a storm surge as a result of a tropical cyclone, a tsunami or a high tide coinciding with higher than normal river levels. If a dam fails, triggered for example by an earthquake, the downstream area will flood, even in dry weather conditions.

Other factors which can contribute to flooding include:

  • volume, spatial distribution, intensity and duration of rainfall over a catchment
  • the capacity of the watercourse or stream network to carry runoff
  • catchment and weather conditions before rainfall
  • ground cover
  • topography
  • tidal influences.

The average annual cost of floods is $32 Bilion (measured in American dollars). Since the year 2000 floods have cost the U.S economy an estimated $850 bilion.

How does a flood event occur?


River floods

Flooding can occur when flow rate exceeds the capacity of a river channel, causing waterways to overflow and damage surroundings.


Flash flooding

Low lying areas are prone to dangerous floods, with high volumes of water causing fierce flooding.


Severe Storms

Hurricanes and thunderstorms cause excessive rainfall, leading to an accumulation of water in low-lying regions.



Ocean-borne earthquakes and volcanic eruptions can lead to large, destructive waves, resulting in large-scale damage and loss of life.


Ice melting rising tides

Melting glaciers increase overall water levels & with no place to contain it, submerge large parts of land mass.

Global flood events are on the rise

Would you know what to do when disaster strikes?

Section1 Section2 Section3 Section4 Section5 Section6 Section7 Section8 Section9

Like to learn more about the Krisis Flood Bag?

Scroll to Top