Effectiveness of the flash flood warning value chain: case study analysis of three recent high-impact events in Australia

Flash flooding presents a significant and increasing risk to public safety across many regions of Australia. This type of flooding, which typically occurs over small spatial scales within 6 hours of the onset of rainfall, is often classed as "high-impact, low probability" and is generally difficult to predict. This is because of the uncertainties in forecasting the intensity and spatial-temporal distribution of rainfall and the resulting landscape response. The short timescales associated with flash flooding also mean that there is limited opportunity to warn communities and trigger protective actions during an event.

The flash flood warning value chain is complex and involves several inter-related components (from forecasts, observations and warnings through to communication, decisions and response). There are multiple organisations involved, with differing roles and responsibilities, and information flows through the value chain via various channels.

In order to identify strategies to improve it is important to understand what is working well in the current service and where there are opportunities for development. This requires significant collaboration with partner agencies to identify pain points with the current approach and needs for a future service.

In Australia, the primary responsibility for flash flood warnings lies with the states and territories through emergency services agencies and local councils. The Bureau of Meteorology's role is to provide forecasts, nowcasts and observations for severe weather conditions and to issue warnings for heavy rainfall that may lead to flash flooding.

This study will evaluate the effectiveness of the warning value chain through case studies of three recent high-impact flash flood events in Australia: Adelaide, South Australia, November 2023; Hunter Valley, New South Wales, July 2022; Hobart, Tasmania, May 2018. The case study approach will follow the guidelines used in the World Meteorological Organisation (WMO) World Weather Research Programme (WWRP) High Impact Weather Warning Value Chain project. This project uses a multidisciplinary approach combining physical and social science with practitioner perspectives to examine the end-to-end function of the warning service.

The outcomes of the analysis will include recommendations to help frame how future services and products can be developed to provide usable and useful intelligence to emergency services agencies and to the broader Australian community during flash flood events.