ALM UNDP

Summary:

Executive Summary

Australia is experiencing extreme climatic events of many types: rainfall and associated floods, drought and associated bush fires, extreme temperatures and associate health risks are just three prominent examples. Underlying all extreme climatic events is the climate data. In the case of extreme rainfall events there are very few examples of examination of multiday extreme precipitation events applying both historical data and future General Circulation Model projections of climatic change. The recent Brisbane flood event of early January 2011 offered the opportunity to assess a multiday extreme precipitation event. The planning and decision making as an outcome of the floods makes the analysis of such multiday events critical so as to inform the process.

The flooding event of January 2011 is viewed in light of the 1974 flood event as it led to a risk assessment and the investment in infrastructure, the Wivenhoe dam, to limit the risk of a similar event. In fact, the Somerset dam, built in 1953 was also designed to reduce the risk of flooding. The assessment of the seven day rainfall of the recent flood exemplifies the trend toward greater magnitude rainfall events with the passage of time. The analysis also points to a shift in extreme rainfall regime from the pre-1980 period to a post-1980 period and when general circulation models are applied the trend toward more intense extreme precipitation events into the future is reinforced. The shortening of return periods for extreme precipitation events and greater intensity of such events has implications for planning and decision making of durable infrastructure along with emergency services planning, landuse regulation and building codes. This relates not only to possible flood mitigation strategies such as the potential need for additional flood mitigating infrastructure but also for the current built environment. The outputs generated through the application of SimCLIM modeling of extreme rainfall events can be integrated with hydrological and flood models so that risk scenarios can be constructed for future time periods. The risk posed by extreme rainfall events is clearly evident socially, economically and environmentally. A climate and climate change assessment as exemplified in this report can provide the foundation for other sectoral risk assessments.

Source: Analysis of the January 2011 extreme precipitation event in the Brisbane River Basin, A CLIMsystems Technical Report. Prepared by: Dr Peter Urich, Dr. Yinpeng Li, Dr. Peter Kouwenhoven, Dr. Wei Ye, 2011.

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