East Coast Lows strike again: NSW’s battle with flooding
The Mid North Coast and Hunter regions in New South Wales faced extensive flooding in May 2025. Prolonged intense rains filled major rivers like the Manning and Gloucester rivers and brought record-breaking 24-hour rainfalls to Taree and Port Macquarie. The main cause of this event was an East Coast Low (ECL) that met with a stationary front to the south, which formed an atmospheric river system. East Coast Lows have consistently caused major flood events in the largest cities in Australia.
East Coast Lows and their threat to Australia
East Coast Lows are low pressure systems that develop from a deep trough in the upper atmosphere over eastern Australia (Figure 1). These low pressure cells often interact with high pressure systems, drawing their energy from strong ocean temperature gradients, coastal convergences (where winds meet near the coast), and moist sub-tropical air at the surface (Harper & Granger, 2002). Strong interactions between pressure systems can result in torrential rainfall, severe windstorms, and large waves, which cause extensive flooding and coastal erosion (National Environmental Science Programme, 2021). These ECLs can develop quickly, causing them to be one of the most dangerous weather phenomena on Australia’s east coast (BOM, n.d.).
ECLs pose a significant threat to Australia’s population. Given that 70% of Australia’s population resides in active ECL regions, namely, southern Queensland, New South Wales and eastern Victoria (Australian Bureau of Statistics, 2024), ECLs can cause major losses across large swathes of Australia. JBA’s Australia Flood Model shows that half of the market exposure at risk of flooding in Australia is on the east coast. Furthermore, 8 out of 10 of the most at-risk local government areas (LGAs) identified by the Insurance Australia Group are in New South Wales, while the remaining most at-risk LGAs are in Queensland (IAG, 2020).
Meteorological development of the May 2025 event
In May 2025, an intense coastal trough developed off eastern Australia. Further south, a static area of high pressure channelled a stream of moist air from the Tasman Sea into the trough, known as an atmospheric river (ABC News, 2025f). Low pressure at the trough uplifted the warm, humid air to produce dense cloud systems and heavy rains over New South Wales.
The Bureau of Meteorology (BoM) reported that the system produced extreme precipitation over a 4-day period from 18 May to 21 May, due to the static nature of the system. This resulted in rainfall of 533mm at Careys Peak, 463mm at Taree and 354mm at Port Macquarie, with the latter two sites recording 24-hour accumulation records (ABC News, 2025f; SBS News, 2025).
From 22 May onwards, the trough deepened into an East Coast Low which brought intense rainfall as the system tracked southwards along the NSW coast (ABC News, 2025f). This mechanism fuelled additional downpours into 23 May, affecting areas further south (including the Lower Hunter, Blue Mountains, and Southern Highlands) before the rain finally eased with the low’s southward departure (ABC News, 2025a). The Manning River at Taree peaked above 6.3 m, surpassing a flood record that had stood since 1929 (BBC, 2025a). The combination of already saturated catchments and intense rainfall led to major and prolonged flooding in multiple river basins.
Climate change is likely to affect the frequency and intensity of ECLs. In a warmer climate, projections show that there will likely be fewer ECLs overall, but an increase in maximum rain intensity and the number of ECLs associated with heavy rainfall (Pepler et al., 2016). For every degree Celsius of warming, rainfall intensity associated with ECLs could increase by 7% for widespread or long duration extreme rainfall events, and 15% for short-lived localised extreme rainfall events, having significant consequences for Australia’s flood risk (Dowdy et al., 2019). This effect is more evident in ECLs nearer to the coast as interactions with ocean currents and the sea surface temperature fuel higher rainfall intensity (National Environmental Science Programme, 2021).
May 2025 flood impacts and damages
Severe flooding submerged residential neighbourhoods and rural communities across parts of NSW’s Mid North Coast and Hunter area, leaving 50,000 people stranded at the peak of the event. By 22 May, 153 flood warnings were active statewide, including major flood warnings for the Manning, Gloucester, Hastings and Macleay Rivers (ABC News, 2025a). A state natural disaster declaration was made on 21 May to mobilise funds and assistance for affected regions, with over 2,200 emergency service personnel involved in this flood event (ABC News, 2025c). Despite the strong effort by the NSW State Emergency Services (SES) to respond to over 535 flood rescues in the first 24 hours of the event, which saved over 300 people (BBC, 2025a), five lives have been lost in the floods (CNA, 2025a).
Across the flooded districts, thousands of hectares of pasture and crops (such as dairy, beef, and horticulture farms) were underwater, which will likely impact agricultural output in the coming months. Farmers around Taree and Kempsey reported devastating livestock losses as cattle and other livestock were swept away by torrents, some ending up on Old Bar Beach after being carried by the Manning River (ABC News, 2025g). Feeding the herd that survives will be a key issue for farmers due to the loss of pastureland in waterlogged grounds and the compromised hay production due to droughts in Western Australia (ABC News, 2025g). The NSW government has provided emergency fodder drops, veterinary care and management advice to affected farmers (CNA, 2025b), but many are hoping for further government support as they were still reeling from the impacts of Ex-Tropical Cyclone Alfred earlier this year and the 2021 and 2022 historic floods when this event struck (The Guardian, 2025a).
An estimated 10,000 properties have been damaged on the NSW Mid North Coast, and preliminary damage assessments by authorities declared almost 800 properties uninhabitable (The Guardian, 2025b). While the loss reserve for the event has not been reported yet, the Insurance Council of Australia (ICA) has declared this an “Insurance Catastrophe”. As of 29 May, insurers have received more than 7,300 claims from the event since 17 May, with nearly 80% of the claims related to home damage (ICA, 2025a). New South Wales State Emergency Services has also completed 12,020 damage assessments on impacted properties, where at least 300 had previously been confirmed to have been damaged beyond repair (NSW SES, 2025a and NSW SES, 2025b).
Past events and lessons learnt
Residents of NSW have experienced numerous large flood events, with farmers and businesses still recovering from the 2021 and 2022 floods. The cause of the 2021 and 2022 floods is notably similar to the current event. In the wider climatological context, the previous two events occurred during periods of La Niña, which is usually associated with higher rainfall in Australia. However, the present event comes after the La Niña season has ended, making this a single extreme weather event rather than part of a multi-month wet period.
As communities continually build experience in coping with flood events, there has been commendable effort by the NSW government, farming organisations and other groups in fostering resilience to flood events since the NSW 2021 floods. For example, the Storm and Flood Industry Recovery Program was launched by the Department of Primary Industries after the NSW 2021 floods to help farmers better prepare, respond and build competencies to tackle future floods better. The Insurance Council of Australia is also pushing for AUD 30.15 billion Flood Defence Fund to help the most flood-prone states - Queensland, New South Wales and Victoria - strengthen their flood defences and implement government buy-back schemes to mitigate losses to future floods (ICA, 2025b).
Reflections
Australians living along the eastern coast have faced a challenging year in terms of flooding, with multiple significant events occurring in succession. This has made recovery efforts difficult and strained the distribution of resources. According to a report released by the Treasury of Australia two months ago, the nation’s 2025–26 Contingency Reserve has already been reduced by AUD 1.2 billion by the end of March due to recent natural disasters (Treasury of Australia 2025). Weather data shows that Australia experienced an exceptionally wet start to the year, with several catchments in Queensland receiving rainfall that exceeded the annual total in 2024 (Figure 2).
These conditions highlight the increasing financial and logistical pressures posed by climate-related events. As extreme weather becomes more frequent and intense, proactive investment in disaster resilience, infrastructure, and emergency planning will be essential to mitigate future impacts. JBA Risk Management has produced event footprints for the recent Australian floods:
1. North Queensland Floods in February
2. Ex-Tropical Cyclone Alfred in March
3. Mid North Coast and Hunter Floods in May
Across these three events, our model estimates a combined insured loss of nearly AUD 3 billion. All loss estimates are generated from JBA Risk Management’s new Australia Inland Flood Model which includes fluvial and pluvial flood perils. This report is accompanied by a flood footprint for the event, detailing extents and depths of the flooding in areas affected in North Queensland. Download it via our Client Portal or request a copy by emailing eventresponse@jbarisk.com.
