Meteorologists anticipate the risk of severe rainfall. Hydrologists summarize this rainfall into predictions about what the flood will be like in terms of depth, flow, and speed. Engineers plan roads, bridges, and buildings to endure the likely conditions, while planners ensure that new development is compatible with flood risks.
No step in this procedure is easy, and the maximum is getting harder. Climate change is deteriorating because a hotter atmosphere can carry more water vapor which supercharges clouds. A hotter climate delivers more energy to lift wet air high into the atmosphere, where it cools, transforms to liquid, and forms extreme rainfall. In Australia’s north, the intensity of heavy rainfall events has risen by 10% since 1979.
It’s tough to predict the risk of extreme storms like those that caused devastating flooding in parts of New South Wales and Queensland this year. Because of these storms, the past is not a good guide to the future. Those floods occurred from a “rain bomb” which released 60% of southeast Queensland’s average annual rainfall in only three days.
Australia has strong guidance available to predict flood risk. The federal government’s Australian Rainfall and Runoff guidance is world-leading. However, to utilize this properly, one needs to undertake high-quality analysis, detailed physical modeling, and thoughtful uncertainty analysis. This can be costly, requiring specialized software, well-trained experts, and enough data and time. That’s why many planners in Australia and globally still turn to more straightforward procedures of flood assessments like the Rational Method.