Severe thunderstorms and flash floods in Victoria
Flash floods occur when soil absorption, runoff or drainage cannot adequately disperse intense rainfall. The most frequent cause of flash flooding is from slow-moving thunderstorms. These systems can deposit extraordinary amounts of water over a small area in a very short time. Flash floods are extremely dangerous weather events as water in creeks, drains and natural watercourses can rise very rapidly.
The radar animation above is from the Melbourne Flash Flood that occurred 3rd December 2003 (see recent examples below)
The strong updrafts of air within thunderstorms can suspend huge amounts of rain before releasing a deluge onto the ground. Such rain can reach intensities of more than 100 mm per hour, provided the environment is humid enough to feed sufficient moisture to the storm. Often topography acts to focus thunderstorm development over a particular location, further accentuating rainfall accumulation.
Recent examples of flash flooding in Victoria include: