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BAMOS August 2025
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Gloucester River, Hastings River, Wollombi Brook, Macleay River, Paterson River, and Williams River.
Homes destroyed and schools closed
The prolonged nature of the system resulted in significant impacts. Emergency services responded to hundreds of flood rescues throughout the event. More than 50,000 people were isolated in the impacted region, with many rescued from their roofs when stranded in flood waters. There were 4 direct fatalities.
Major road and rail links were closed due to flooding, debris, or landslides, including parts of the Pacific Highway, Oxley Highway, Waterfall Way, as well as the Hunter, Central Coast / Newcastle, and Southern Highlands rail lines. Many regional schools were closed for several days, with thousands left without power for more than 24 hours. Agricultural and livestock losses were substantial.
What can we expect in the future?
While east coast troughs are a regular feature of Australian weather, they can result in catastrophic impacts due to their interaction with blocking high-pressure systems and their potential to deliver high rainfall totals over multiple days.
Similar flooding events have occurred in eastern New South Wales in the past. Notably, along the Hawkesbury & Nepean Rivers in March 2021 and 2022, and the Wilsons River at Lismore in March 2022. These events have highlighted the vulnerability of east coast communities to slow-moving rain-bearing systems.
Looking ahead, the State of the Climate 2024 report states:
" Climate change may affect the drivers of, and processes involved in, multi-day rainfall extremes. These include atmospheric rivers which are responsible for the transport of large quantities of moisture, the behaviour of El Niño and La Niña, and persistent blocking highs( strong high-pressure systems that remain almost stationary for an extended period of time, blocking the eastward progression of weather systems across southern Australia) in the Tasman Sea. The details of these effects are subject to ongoing research."
Figure 1: Mean Sea Level Pressure( MSLP) analysis chart at 10 am AEST on 22 May 2025( left) and 23 May 2025( right). Credit: Bureau of Meteorology
Figure 2: Total accumulated rainfall between 19 and 23 May 2025. Credit: Bureau of Meteorology