Ten Years on: Brisbane’s Compounding Flood Risk

Abstract

It is over 10 years since Brisbane experienced the devastating 2011 flood. Reaching 4.46 m AHD in the Central Business District (CBD) at its peak, the flood was estimated as equivalent to a 1 in 100 (1%) Annual Exceedance Probability (AEP) event. Despite the catchment’s hydrological history recording four larger floods since British settlement in 1824, the 2011 event caught many residents off-guard, with the community expressing shock at the consequences of a major flood event in this sub-tropical catchment. Media reports, community folklore and the Queensland Floods Commission of Inquiry revealed the deep-seated myth that Wivenhoe Dam had “flood-proofed” Brisbane. The findings of the subsequent class action further reinforced the misconception that flood events can be largely prevented by dams. In doing so, development of the region’s flood prevention, preparedness and resilience strategies was impeded, and urban areas continued to expand. The hazard compounded. This chapter uses the 10-year anniversary of those floods to benchmark the present and future flood risk in the Brisbane River floodplain. Already identified as the most flood-impacted catchment in Australia, without management, future development and continued population growth will increase the flood risk. This challenge is intensified further by the anticipated changes in rainfall and sea level from climate change. Current modelling indicates that by 2050 a 1 in 100 AEP event will be between 1.2 m and 2.5 m higher in Brisbane’s CBD. The 2011 floods proved a catalyst for change prompting research and new policy and legislative initiatives in Queensland over the last decade. This chapter asks, can this increased knowledge overcome the compounding risks in this complex catchment and better prepare the region for the next major flood?