'Freak’ rain event drove flash flooding

Last Thursday’s rainfall was extraordinary, so extraordinary that it was rated a 'freak' occurrence in some sections of the Sunshine Coast.

The Bureau of Meteorology recorded falls of up to 351mm over a six hour period. Sunshine Coast Council Executive Director for Infrastructure Services, Andrew Ryan, said the significant flooding that occurred on some major roads was a direct result of the severe rainfall.

"The heavy rainfall on the afternoon and evening of 22 March exceeded the design capacity of many council and state controlled roads," he said.

"For the period of this extraordinary downpour, local drainage infrastructure was overwhelmed and this resulted in the significant flooding that was seen along major roads like the Nicklin Way and Alexandra Parade.

"The majority of the rainfall fell in less than six hours which produced flash flooding simply because the rain was so intense that it had nowhere to escape."

Bureau of Meteorology recorded the following rainfall amounts between 1:30pm and 7:30pm on Thursday 22 March:

• Parrearra Weir (351mm)
• Bundilla Blvd, Mountain Creek (324mm)
• Meridan Plains (286mm)
• Sugarbag Rd Caloundra (285mm)
• Maroochydore Depot (261mm)
• Picnic Point Maroochydore (218mm)
• Dixon Rd Mountain Creek (196mm)

Mr Ryan said council surveyors have already started taking measurements of the flood heights from the recent flooding events that occurred in February and March.

"This information will assist council’s flood engineers in producing a flood map for this event which will show the extent of the flood," he said.

"Council’s flood engineers will also produce similar maps for the floods that affected Pomona, Cooroy and Cooran at the end of February.

"These maps will be made available to the public later this year."

An advisory message will be posted on council’s website when the maps are available for public viewing.