A flood is an overflow of water beyond the normal limits of a watercourse such as a lake, river, or creek. It can also happen when water is released from a reservoir, canal, or dam. The most common cause of flooding is heavy rainfall.  

Flooding poses a significant challenge to communities across the country, and effective management requires a combination of infrastructure improvements, early warning systems, and ongoing adaptation to climate change's impacts. 

Water released from Wivenhoe, Somerset, and North Pine Dams is often mentioned when we think about floods, but it represents only one of many sources of flooding.  

Types of flooding 

River flooding 

River flooding in Australia often results from intense or sustained rainfall events that cause rivers to overflow their banks. In regions like South East Queensland, river flooding can be a regular occurrence, especially during wet seasons or La Niña weather patterns, which bring heavy rainfall across eastern Australia. As we know, the Brisbane River is particularly vulnerable to flooding. 

Coastal Flooding (Storm Surge and King Tides) 

Coastal flooding is caused by high tides, tropical cyclones, or storms pushing seawater onto coastal areas.  

Australia's coastline is prone to storm surges, especially during tropical cyclone seasons (November to April). When cyclones make landfall, strong winds can push seawater onto coastal areas, causing significant storm surges. "King Tides" is a term used to describe the highest tides in a year. They are part of the natural tidal cycle but can also lead to coastal flooding, especially when they coincide with storm events or heavy rainfall. 

Flash Flooding 

Flash flooding is a result of intense, short bursts of heavy rainfall over a small area in a short amount of time. It is particularly common when storms develop rapidly due to a combination of intense heat, moisture, and atmospheric instability. 

Tropical Cyclone-Induced Flooding 

Tropical cyclones produce strong winds and intense rainfall, which can cause widespread flooding by dumping heavy rainfall over large areas.

For more information:

• Get Ready Queensland - Floods https://www.getready.qld.gov.au/getting-ready/understand-your-risk/types-disasters/flood
• Bureau of Meteorology - Understanding floods http://www.bom.gov.au/australia/flood/knowledge-centre/understanding.shtml