The Hawkesbury-Nepean Valley has some of the most dangerous floods in the region. The valley covers approximately 425 square kilometres in Western Sydney from Bents Basin near Wallacia to the Brooklyn Bridge.
The last major flood was in 1990. Five of the biggest floods in the past 150 years have occurred since 1961. Most floods have occurred after a period of drought.
It’s important you understand your flood risk. These maps show you the impact of the worst flood on record in the region. Get to know how your area could be affected.
The map on the right shows the extent of the worst flood on record.This flood has a 15% chance of happening in an 80-year lifetime. It is also referred to as a 1 in 500 chance per year flood. It last occured in 1867.
Downstream of Cattai Creek near Ebenezer, the Hawkesbury River enters gorge country which continues all the way to Brooklyn. Along these gorges, flooding can occur between the river bank and the valley sides.
Communities and recreational / caravan parks close to the river in this area are at risk from flooding, including Sackville, Cumberland Reach, Lower Portland, Webbs Creek, Lower Macdonald, Wisemans Ferry, Gunderman, Laughtondale and Spencer.
Due to the steep gorges, roads in the Lower Hawkesbury are often close to the river and are cut by relatively small floods.
While every flood behaves differently, the flood descriptions here have been developed from the latest flood modelling and mapping.
The map on the right shows the extent of the worst flood on record.This flood has a 15% chance of happening in an 80-year lifetime. It is also referred to as a 1 in 500 chance per year flood. It last occured in 1867.
The Richmond/Windsor floodplain covers a large area including Windsor, South Windsor, Bligh Park, Londonderry, Agnes Banks, Clarendon, Richmond, parts of North Richmond, McGraths Hill, Oakville, Mulgrave, Pitt Town, Hobartville and parts of Wilberforce. To the east, it includes parts of Maraylya, Cattai and Ebenezer.
Even in frequent floods, there is extensive flooding of low-lying areas between Richmond and Pitt Town. The Yarramundi, Windsor and Richmond bridges go under water in floods with almost a 100% chance of occurring in an 80-year lifetime.A flood this size is also referred to as 1 in 5 chance per year flood.
In a flood with a 98% chance of occurring in an 80-year lifetimeA flood this size is also referred to as 1 in 20 chance per year flood. the Richmond/Blacktown railway line would be closed.
In a flood with a 55% chance of occurring in an 80-year lifetime,A flood this size is also referred to as 1 in 100 chance per year flood. there would be widespread flooding creating flood islands including Pitt Town and Windsor.
Many evacuation roads would be cut including the Hawkesbury Valley Way at the Jim Anderson Bridge. When this road is cut residents from Windsor and South Windsor will not be able to evacuate. McGraths Hill would be fully submerged. See detailed information about evacuation routes.
If the worst flood on record happened today, flood depths would be nearly 2.5 metres higher, reaching around 19 metres above normal river level at Windsor. A flood this size happened in 1867 and has a 15% chance of occurring in an 80-year lifetime. A flood this size is also referred to as 1 in 500 chance per year flood.
A very large number of properties would be directly impacted in the suburbs listed above, as well as in Bligh Park, Richmond and Hobartville.
Electricity supplies would be cut within the region and some properties outside the floodplain could be without power for days or even weeks. Evacuations would be necessary for flooded areas affected as well as for other areas that may also become isolated or lose their services/utilities.
While every flood behaves differently, the flood descriptions here have been developed from the latest flood modelling and mapping.
The map on the right shows the extent of the worst flood on record.This flood has a 15% chance of happening in an 80-year lifetime. It is also referred to as a 1 in 500 chance per year flood. It last occured in 1867.
The Penrith/Emu Plains floodplain includes parts of Penrith CBD, Thornton Estate, South Penrith, Regentville, Jamisontown, Emu Plains, Emu Heights, Leonay, Penrith Lakes, Castlereagh and parts of Cranebrook. It includes the recreational areas adjacent to both banks of the Nepean River.
During a flood with a 55% chance of occurring in an 80-year lifetimeA flood this size is also referred to as 1 in 100 chance per year flood, floodwaters escape the banks of the river, flooding parts of Emu Plains and areas adjacent to Peachtree and Boundary creeks in Penrith. The Western Motorway (M4) at South Creek could be closed by local flooding.
If the worst flood on record occurred today much of Emu Plains would be inundated and floodwaters would extend east as far as Woodriff Street in Penrith. A flood this size happened in 1867 and has a 15% chance of occurring in an 80-year lifetime.A flood this size is also referred to as 1 in 500 chance per year flood.
In such a flood, there would be road closures including the Great Western Highway. Evacuations would be in place for large parts of the floodplain. Buildings and low-lying carparks in parts of Penrith’s CBD would be impacted. Thousands of homes are likely to be without power and other essential services would be impacted for days or even weeks. See detailed information about evacuation routes.
While every flood behaves differently, the flood descriptions here have been developed from the latest flood modelling and mapping.
The map on the right shows the extent of the worst flood on record.This flood has a 15% chance of happening in an 80-year lifetime. It is also referred to as a 1 in 500 chance per year flood. It last occured in 1867.
Floodwaters from the Hawkesbury River can back up into South Creek and Eastern Creek causing flooding in adjacent suburbs.
In a flood with a 55% chance of occurring in an 80-year lifetime, A flood this size is also referred to as 1 in 100 chance per year flood. the floodwaters would inundate properties in Windsor Downs, Berkshire Park, Shanes Park and Llandilo. The Richmond Road evacuation route would be cut at South Creek Bridge. Along Eastern Creek, backwater flooding would impact properties at Vineyard, Riverstone and Schofields. See detailed information about evacuation routes.
If the worst flood on record occurred today, the backwater effects would be higher and extend further, impacting more properties including Marsden Park. A flood this size happened in 1867 and has a 15% chance of occurring in an 80-year lifetime. A flood this size is also referred to as 1 in 500 chance per year flood.
Flooding from the local catchments could inundate land further upstream beyond the influence of Hawkesbury River backwater.
While every flood behaves differently, the flood descriptions here have been developed from the latest flood modelling and mapping.
The map on the right shows the extent of the worst flood on record.This flood has a 15% chance of happening in an 80-year lifetime. It is also referred to as a 1 in 500 chance per year flood. It last occured in 1867.
The Wallacia floodplain includes parts of Wallacia and Greendale, rural parts of Mulgoa, and Bents Basin State Recreation Area.
This floodplain is in a small and confined valley, and it has the potential for deep flooding. Floodwaters from the Nepean and Warragamba rivers back up as it cannot flow freely downstream due to narrow gorges between Wallacia and Penrith.
Key roads can be cut off by flooding. Silverdale Road, the road from Wallacia to Warragamba, is cut by floodwaters at Blaxlands Crossing in frequent floods that have almost a 100% chance of occurring in an 80-year lifetime.A flood this size is also referred to as 1 in 5 chance per year flood.
The Park Road evacuation route from Wallacia to the east is cut in a flood that has a 98% chance of happening in an 80-year lifetime.A flood this size is also referred to as 1 in 20 chance per year flood.
If the worst flood on record happened today all key evacuation routes would be cut. A flood this size happened in 1867 and has a 15% chance of occurring in an 80-year lifetime.A flood this size is also referred to as 1 in 500 chance per year flood. Hundreds of homes are likely to be without power and other essential services would be impacted for days or even weeks. See detailed information about evacuation routes.
In an extremely rare flood (the probable maximum flood), the village of Wallacia would be completely inundated.
While every flood behaves differently, the flood descriptions here have been developed from the latest flood modelling and mapping.
Floodplain profile
It’s a fact that floods in the Hawkesbury-Nepean can be some of the most dangerous in Australia.
The maps above give you an idea of the extent of flooding that can happen in the valley. If a flood similar to the largest flood on record happened in the valley now, more than 90,000 people would need to be evacuated and more than 12,000 homes would be impacted by floodwaters.
The information below will help you understand why floods are so dangerous here, the impacts of past floods, and importantly how to understand the meaning of risk and likelihood when it comes to flooding.
First you need to understand your flood risk, then take the next steps to prepare for floods now.
View this video to understand why floods are so deep and dangerous in the Hawkesbury-Nepean Valley. Learn how the ‘bathtub effect’ causes floodwaters to back-up and cause deep and dangerous flooding.
The Hawkesbury-Nepean Valley has a long history of damaging and dangerous floods. Five of the 10 largest floods since the record flood of 1867 have occurred since Warragamba Dam was completed in 1960. The last major flood was in 1990. View remarkable footage of the impacts of these significant floods.
Know your risk
Understand where to go
Know who to call
Prepare a home emergency kit 
Check your insurance
Know when to act during a flood emergency
