[+] NSW Flood Planning Evolves as Crisis Unfolds

NSW is in the middle of the largest flood response operation in the history of the state, with flooding this week in the central west expanding the scope of that recovery. With these disasters set to become more, not less, frequent as climate change rips up the flooding rule book, property sector stakeholders are calling for flood-risk mapping to undergo a step-change. Forbes and surrounding areas in the state’s central west were evacuated for the second time in a fortnight, while Gunnedah was evacuated because of a sixth major flood this year. For the first time in its history, the SES has called in international support, receiving defence and other emergency support as it evacuated towns by helicopter and boat. But flood experts and property stakeholders say that extreme inundation levels of recent years need to be planned for, not planned around. The current level of technology, and the frameworks around modelling future flood risk, are not yet fit for purpose, according to planners, researchers, and other property players. As the climate continues to change in coming decades, the regions that will be newly exposed to flood risk have not yet been identified. Planning Institute of Australia policy national policy manager John Brockhoff told The Urban Developer, “We’re planning for floods in a changing climate”. “We’re also managing strong growth in regional Australia. Those two things together, if we’re planning for it, mean more uncertainty around the climate and natural environment, bushfires and floods,” he says. “We’ve got to take a more conservative approach to the way we do our long-term planning, so that we’re not putting lives and property at risk.” ▲ Floods need to be planned for, not planned around, say experts. Future flood risk to worsen More work is needed to determine where future floods will occur, and the extent of their impact, but it’s certain that they are likely to be more extreme, researchers say. Dr Chiara Holgate, a research fellow at the ARC Centre of Excellence for Climate Extremes, says that “our research shows that rainfall in eastern Australia is maximised when a particular set of climate drivers act in concert”. “Of course, while the number and extent of floods this year seem unusual in the context of recent decades, it is my understanding that the extent to which it is actually unusual has not yet been scientifically established.” Research recently undertaken with the support of the water infrastructure industry has revealed that current rainfall models need to be updated to account for climate change. The paper estimates that rainfall catchment by 546 large dams across Australia is expected to increase between 14 and 38 per cent under a changing climate. Under the current flood risk mapping model, the increase in rainfall already observed over the past 20 years is not taken into consideration, let alone future increases. Johan Visser of UNSW’s Sydney’s Water Research Centre, the lead author on the paper, says that “under any future scenario, our estimate is that the [Predicted Maximum Precipitation] will increase”. “The observational data shows that atmospheric moisture has been increasing over the historical record, and when you also factor in future climate projections from climate models, then you see that it’s projected to increase even further into the future. “Dam owners regularly review the safety performance of their dams under a wide range of failure scenarios, and this research reinforces the importance of ensuring that in the future these reviews consider the implications of a warming climate on extreme floods.” ▲ Dam performance is crucial to planning for future flooding events. Co-author Professor Ashish Sharma of UNSW’s School of Civil and Environmental Engineering says that anybody planning to build a large dam “needs to think 50 to 100 years ahead”. “This research makes clear that future planning now needs to consider the future impacts of climate change on the plausible upper limit of rainfall extremes.” Spatial science can help FrontierSI is a not-for-profit company that provides research and advice to government and industry on spatial science and infrastructure. The company recently released a report investigating how urban planners and the property sector can integrate earth observation (or satellite) data into their practices. In terms of flood-risk mapping, that information can be used to understand, for example, runoff flows in urban networks, or the impermeability of land surfaces over large, or more granular, scales. Under the right applications, it can also be used in projecting future flood risk. FrontierSI industry engagement manager Dr Serryn Eagleson says that “there’s increased availability of satellite data, coupled with machine learning and AI and sensor data. What we need to do now is better co-ordination across all these different data streams”. According to Eagleson, many urban planners are also currently relying on off-shore providers of expensive data. Mapping Australian flood risk will require more high-resolution imagery available at reasonable cost. But one of the major sticking points, and a current focus for FrontierSI, is in awareness and understanding within the property sector. ▲ The spatial and property sectors need to get on the same page. “One of the things we’re trying to do is talk about language. People in spatial science and people in the property sector, speak a different language. So we need to get together, we need to train the next generation,” Eagleson says. “We need models that we trust, we need data in the conversation…we need to deal with awareness and training in this data because it’s quite new. “What it’s really about is how do we embed up-to-date data science into the planning process, from day one.” Planners call for clarity, consistency Brockhoff argues that the NSW government needs to take a larger role in assisting planners and councils to map future flood risk, and is pleased by indications that it’s moving in that direction. “It falls on the resources of individual councils, which have different degrees of resources, to do the mapping, apply the right parameters and assumptions, and to update the model with new information and new technology,” he says. “Where state government can play a role is in providing some of the common parameters, common briefs, common data requirements and formats, and common assumptions for the models. That will play a role in driving greater efficiency, so local governments don’t have to reinvent the wheel each time.” While financial assistance and common guidelines are important, according to Brockhoff, the state government also needs to provide a clear framework for decision-making around flood risk. New flood planning, recovery body In response to years of flooding turmoil in the state, planning minister Anthony Roberts introduced a Bill for a NSW Reconstruction Authority on November 9. The establishment of the authority was a recommendation of the independent inquiry established in response to the 2022 Northern Rivers floods. ▲ The NSW Reconstruction Authority was a recommendation of the independent inquiry after 2022 Northern Rivers floods. A DPIE spokesperson told The Urban Developer that the authority will “be responsible for facilitating disaster prevention, preparedness, recovery, reconstruction, and adaptation for the impacts of disasters in NSW”. “Some of the authority’s key responsibilities will be to develop a state disaster mitigation plan, carry out flood modelling, and set new flood planning levels, particularly for high-risk catchments. Flood modelling and other evidence-based data will help to improve land-use planning decisions.” However, specifics of how the authority will undertake flood modelling, and co-ordinate flood planning, are not yet clear. The Bill also provides the planning minister with wide-ranging powers to declare an area or project a disaster zone, or potential disaster zone. Declarations will be made on ministerial discretion, and are not statutorily required to take any particular information or process into account. The DPIE spokesperson says that the Bill includes “broad powers and functions for both the authority and Minister for Planning to ensure affected communities can better prepare for and recover more quickly from the impact of natural disasters, including the ability to work with communities through councils to develop local adaptation plans and, in certain circumstances, declare projects to deliver them faster when needed”. The NSW Reconstruction Authority Bill 2022 has passed into the senate, and the government’s intention is to pass the Bill into law this year. However, with only a handful of sitting days left in the year, and a caretaker period expected before the March 25, 2023, NSW state election, the timeline for passage of the Bill, and the authority’s establishment, remains unclear. Planning Minister Anthony Roberts was approached for comment. You are currently experiencing The Urban Developer Plus (TUD+), our premium membership for property professionals. 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[+] NSW Flood Planning Evolves as Crisis Unfolds

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