South East Queensland
17.5 Overbank flood spilling

Supporting Information

a. Overall

This process occurs in the South East Queensland (SEQ) region, but the volume could not be quantified in a way that is complete, neutral and free from material error due to the lack of both data and a suitable quantification approach.

b. Flood summary

Significant flooding occurred within the SEQ region in January 2011, with devastating effects upon the community. Record river heights occurred in the Lockyer Creek, and unprecedented flash floods caused significant damage and deaths in a number of towns. Flooding occurred throughout a number of Brisbane suburbs, including the central business district when the Brisbane River broke its banks and reached heights not seen in 30 years (Queensland Floods Commission of Inquiry 2011). The Bremer River flooded and inundated the Ipswich central business district, also reaching heights not seen in 30 years (Queensland Floods Commission of Inquiry 2011).

Despite the overbank flood spilling and return to river channel being significant in volume during these floods, the volume was not able to be quantified. However, as neither the overbank flood spilling nor return to river channel could be quantified, the impact of these omissions on the water balance of the surface water store is considered to not be material. Although some flood waters would have replenished groundwater within the region, and evaporation or other losses of flood waters would have occurred, most of the overbank flood spilling would have returned back to the river channels.