Flood Mitigation and Feasibility: Lessons Learned Across South-East Australia

Abstract

Floods are the most expensive natural disaster in Australia and are responsible for an estimated $660 million of damage each year on average. Recent decades have seen some of the more severe floods in Australia’s history, with the floods of 2010/2011 being the most damaging in our history with damage costs estimated at over $14 billion (tangible and intangible costs). The assessment of flood mitigation, including the feasibility of such options, is a key skill of floodplain engineers. When considering the feasibility of structural mitigation options there is extensive analysis that typically feeds into a feasibility assessment. This includes undertaking or interpreting accurate modelling on which to base an assessment of impact, undertaking an estimate of flood damages (under existing and mitigated conditions) and estimating realistic construction and maintenance costs. Flood mitigation studies must also have consideration for environmental, heritage and planning implications. This paper will examine key lessons learned from the delivery of numerous flood mitigation studies across NSW, Victoria and Tasmania. It will present key considerations and tips in the areas of modelling, concept design and feasibility assessment. The paper considers a range of structural mitigation options including levees, bridge/culvert upgrades and channel works including the oft suggested option – “clean out the damned creek”. The paper concludes with practical advice on how to improve the likelihood of successful outcomes when undertaking or commissioning flood mitigation projects.