Regional flood estimation in Australia : past, present and future

A major portion of Australia’s population, infrastructure, and industry is located in flood-prone areas. Furthermore, in Australia, floods account for nearly 30 per cent of Australia’s natural disasters. The series of floods that hit Queensland in the summer of 2010-11 killed 28 people, caused $2.3 billion in property damage, and reduced Australia’s gross domestic product by an estimated $30 billion. These estimates, however, neglect the real costs associated with loss of personal possessions, shattered lives and battered communities. There is no doubt, it seems like damaging floods have been in the news daily over the last few years. In 2011 alone, the global flood damage was estimated to be worth $70 billion. While, engineers cannot stop floods from occurring, strategies should be put in place to reduce the risk of large economic losses, environmental damage, and loss of life. Development of economically efficient and floodplain management plans requires good estimates of the risk of flooding. In Australia, the risk computation is done following guidelines in Australian Rainfall and Runoff (ARR) Book 4 “A Guide to Flood Estimation”, for which the latest update was published in 1987. That update included the Probabilistic Rational Method and various local methods for design flood estimation published over 30 years ago. ARR 1987 has served the nation for over 30 years and has also been guide for flood estimation for many other countries. Indeed, it is a remarkable document that has stood the test of time. But it must be recognised, given the long-standing problems associated with some of the methods in the document, recent advances that address those problems, and the current national interest in new design flood estimates, the time has arrived to update Book 4 to maintain the statistical credibility of the national guidelines and to provide accurate risk and uncertainty assessments. The purpose of this paper is three-fold, firstly we present an overview of previously adopted regional flood methods in Australia, we then discuss the scope and status of the research in relation to the upgrade of the ARR and finally we provide some useful information and insights on future directions in regional flood estimation.