2015 Floodplain Management Association National Conference 1 REVISION OF AUSTRALIAN RAINFALL AND RUNOFF – THE INTERIM CLIMATE CHANGE GUIDELINE Bryson C. Bates 1 , Duncan McLuckie 2 , Seth Westra 3 , Fiona Johnson 4 , Janice Green 5 , Jo Mummery 6 , Debra Abbs 1 1 bryson.bates@csiro.au CSIRO Oceans and Atmosphere Flagship, Wembley WA 2 Office of Environment and Heritage, Newcastle, NSW 3 University of Adelaide, Adelaide, SA 4 The University of New South Wales, Kensington, NSW 5 Bureau of Meteorology, Canberra, ACT 6 University of Canberra, Canberra, ACT Abstract This paper describes the Interim Guideline for Climate Change for Australian Rainfall and Runoff (ARR). The Interim Guideline outlines an approach to address the risks from climate change in projects and decisions that involve estimation of design flood characteristics. It draws on the most recent climate science, particularly the release of the Intergovernmental Panel on Climate Change Fifth Assessment Report in September 2013 (IPCC, 2013) as well as the new climate change projections for Australia (CSIRO & Bureau of Meteorology, 2015). The Interim Guideline is intended to be applied to the design standard for the structure or infrastructure of interest. While its primary application is for current-climate rainfall intensities (or equivalent depths) within the range of probability of one exceedance per year or annual exceedance probabilities (AEPs) from 50% to 1%, it provides guidance for situations where the Probable Maximum Precipitation is the basis for design. At the time of writing (March 2015), the Guideline was still open for public comment and thus subject to revision. Introduction Australian Rainfall and Runoff (ARR) is a national guideline document for the estimation of design flood characteristics in Australia. ARR is currently being revised to incorporate an additional 25 years of data since its last publication (1987/1999), to fill knowledge gaps with particular reference to the growth of computerised techniques, and to take into account the effects of climate change. Climate change is expected to have an adverse impact on heavy rainfall intensities (or equivalent depths) which could increase the risk of flooding over time at many locations. The Interim Guideline for Climate Change draws on the most recent climate science, particularly the release of the IPCC Fifth Assessment Report (IPCC, 2013) as well as the new climate change projections for Australia (CSIRO & Bureau of Meteorology, 2015). It outlines an approach to address the risks from climate change in projects and decisions that involve design flood estimation. This paper is organised as follows: first, a review of relevant scientific literature is presented; second, present approaches for incorporating climate change into design flood estimation in Australia, New Zealand and the United Kingdom are described; third, the rationale and structure of the Interim Guideline is described; fourth, a simple