WHAT IS A FLOOD?

A flood results from days of heavy rain and/or melting snows, when rivers rise and go over their banks. Floods occur when water covers land that is normally dry. The main cause of floods in Australia is heavy or long-lasting rainfall, which can make rivers exceed their capacity and overflow. In coastal areas flooding can be caused by tsunamis, very high tides, or tropical cyclones, which cause surges of seawater.

WHAT IS A FLASH FLOOD?

A flash flood is sudden flooding that occurs when floodwaters rise rapidly with no warning within several hours of an intense rain. They often occur after intense rainfall from slow moving thunderstorms. In narrow canyons and valleys, floodwaters flow faster than on flatter ground and can be quite destructive.

 

WHAT CAN MAKE FLOODS WORSE?

– Trees maintain the soil structure, while deforestation increases erosion and makes the land less ‘permeable’ (less able to soak up water). The less water that soaks in, the more will sit on top and may cause flooding. 

– Straight rivers speed up water descent, while meandering ones slow it down. If you have more straight rivers then water will collect in low lying areas faster and may cause flooding. 

– Plants hold the water back, while water rushes off concrete or paved built-up areas. The fewer plants in an area, the more likely it is to flood if there is a lot of water in a short amount of time.