The flooding of the south-east Queensland city of Ipswich in January this year was partially the result of water releases from the giant Wivenhoe Dam and the incessant heavy rain over 5 days on the district.
However, the performance of the dam during the January flood event is said to be more complex than simply assigning flood causation to “dam releases”.
This is a preliminary finding of the Insurance Council of Australia sponsored Hydrology Panel Report on Ipswich Local Government Area (LGA) in the panel’s multi-part examination of flooding in the Brisbane Catchment Area. It was released today.
The report names 4 factors that affected and exacerbated the nature of the flooding in the Ipswich City Area from January 9 to 14.
The factors were intense rainfall on catchments upstream of Wivenhoe and Somerset dams, a “wet” catchment area that caused large volumes of floodwater into Wivenhoe and Somerset, significant releases from Wivenhoe over January 11 and 12 and outflows from Lockyer Creek and Bremer River.
High tail water levels in the Brisbane River and tributary creeks led to backflows up piped drainage systems that led to waterway floodwaters of low-lying areas normally drained by the system.
This 153-page latest of 4 reports – after earlier Brisbane and Toowoomba hydrology reports – says: “It may be more appropriate to assign flood causation to ‘succeeding storm events over the catchment area of the dam (Wivenhoe), each characterised by exceptionally heavy rainfalls and massive surface runoff volumes’.”
Insurance industry personnel working in the insurance recovery and claim handling in the region will not yet have a definitive conclusion of the flood situation of the region.
source: John Heath – InsuranceNewsAustralia.com
