Nepean river flood study

Contact us for any help on browser support. Consultation has concluded. This page will be updated as the study progresses. Council recently completed the Nepean River Flood Study and exhibited it for public comment.

You can view the final study in 2 volumes here:. In response to the findings of that study we are now preparing a Floodplain Risk Management Study and Plan for the Nepean River and its floodplains. This Study and Plan will tell us what flood management measures are required and help us plan for and manage known flood risks. In November we sought your input, as your local knowledge and personal experience are invaluable in helping us plan for and develop effective floodplain risk management measures.

Thank you to everyone who participated. Thank you to everyone who gave us feedback. This is the latest study to be completed and put on public exhibition as part of Council's ongoing floodplain management program. The study aims to establish the mainstream flood behaviour and inform future risk management planning. Continuously updating flood modelling and Council's management plan is essential to ensure the safety and resilience of the community in times of natural disaster.

The Nepean River Flood Study covers Continue reading. IE10 and below are not supported. Google Chrome Mozilla Firefox. Toggle navigation. Search Search. Nepean River Flood Study. Project Updates Consultation has concluded. Draft Flood Study Exhibition.Our department is responsible for surface and groundwater management including ensuring water security for NSW. We ensure the equitable sharing of surface and groundwater resources and that water entitlements and allocations are secure and tradeable.

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nepean river flood study

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Environmental water Learn about water for the environment and what we are doing to improve its management.The flood mapping tool above shows you the flood risk for different suburbs in the valley. If a flood similar to the largest flood on record happened in the valley now, more than 90, people would need to be evacuated and more than 12, 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. The Hawkesbury-Nepean Valley has a long history of damaging and dangerous floods. Five of the 10 largest floods since the record flood of have occurred since Warragamba Dam was completed in The last major flood was in View remarkable footage of the impacts of these significant floods.

Floods are often described in terms of the chance that floods of a certain size might occur. If you live in, work in or visit the Hawkesbury-Nepean Valley you can follow these simple steps NOW to prepare for floods. Make sure you talk with your family and friends about what you will do in a flood so that everyone knows what to do and what to expect. Just a little preparation can save lives. The interactive flood mapping tool provides information at a suburb level.

For more detailed information on risk related to your property or street, please contact your local council. Explaining flood likelihood - graphic. There are three main floodplains in the Hawkesbury-Nepean Valley linked by the river.

If your house or work is within the probable maximum flood PMF area, you are within the floodplain. The PMF is what flood experts have determined is the largest possible flood for the area. Like droughts, fires and storms, floods are unpredictable, damaging and dangerous. The Hawkesbury-Nepean floodplain was created by floods over thousands of years.

More floods will happen and we need to be prepared. Recent research points to a cycle of flood-dominated and drought-dominated periods across the region.

This would suggest we are currently in a drought-dominated period which has included the Millennium Drought. A flood-dominated period is likely to follow this drier cycle. Even in a long drier period, we can still experience a rain event that can cause a flood. The same could happen during the current drought. If you live in the Hawkesbury-Nepean Valley, or even in nearby suburbs, you might be affected by flooding the valley.A large part of Emu Plains extends onto the flood plain but Penrith is located on relatively flood free land.

The lower parts of Penrith can be flooded when water from the Nepean River backs up into various small creeks. Settlers were attracted to the Nepean district by good prospects for agriculture. However, periodic floods which built up the fertile soil along the river banks, at times, caused disastrous losses of crops and buildings.

The first flood on record — apparently a small occurrence — was in Others followed inand The devastation caused by flooding in February, prompted Governor Macquarie to issue a notice exhorting settlers, in the strongest possible terms, to build their residences above the established flood levels. The most devastating flood occurred in Junethe Nepean River being estimated to have reached a height of about This flood carried away the approaches to the recently rebuilt Victoria Bridge.

Emu Plains, Castlereagh and the lower parts of Penrith were all under flood, causing immense loss of property. Many houses were carried into the river by landslides. Many residents were forced to take refuge in public buildings such as the Penrith Hospital and the public schools.

The flood depicted in the Sydney Morning Herald on 24 June There have been other notable floods since — particularly that of July and March Again there was much flooding of streets and loss of houses and property along the river. It called for liaison between local councils and relevant state government authorities in order to reduce flood losses, improve the environment of flood plain areas and collect information and promote research in the area of flood mitigation.

The 1 in year flood level used by Penrith Council is The increased magnitude and frequency of flooding at that time imposed a demand for some protection of flood plains. Geomorphology of the Hawkesbury-Nepean River system. For more information on the history of floods in the Penrith area please visit the Local Studies Room at Penrith Library. Alternatively, have a look at the following websites. For more information on Floods in the Penrith City area:. Email Address. Penrith City Local History.

Skip to content. The flood depicted in the Sydney Morning Herald on 24 June There have been other notable floods since — particularly that of July and March Search Search for:.The Nepean River and its associated mouththe Hawkesbury Riveralmost encircles the metropolitan region of Sydney.

The river flows north in an unpopulated water catchment area into Nepean Reservoirwhich supplies potable water for Sydney. North of the dam, the river forms the western edge of Sydney, flowing past the town of Camden and the city of Penrithsouth of which flowing through the Nepean Gorge.

The river supplies water to Sydney's five million people as well as supplying agricultural production. This, combined with increased pressures from land use change for urban development, means the river has been suffering significant stress. There are eleven weirs located on the Nepean River that significantly regulate its natural flow.

The river has been segmented into a series of weir lakes rather than a freely flowing river and is also impacted by dams in the Upper Nepean catchment. The first Australian fishsteps were built when the current concrete weir was built at the beginning of the Nepean Gorge, an anticendant entrenched meander caused by the slow uplift during the Blue Mountains orogeny carved down through the fifty-million-year-old Hawkesbury sandstone.

These dams and weirs have had a potent effect, blocking migratory native fish like Australian bass also locally commonly known as perch from much of their former habitat, and reducing floods and freshets needed for spawning. The luscious banks of the Nepean River provide a natural haven for local flora and fauna and a quiet location for local residents to relax. At Emu Plains, the western bank of the river provides a location for outdoor theatre productions on warm summer nights. The eastern bank at Penrith provides barbecue facilities and children's play equipment, as well as a wide pathway running for several kilometres for strolls along the riverbank.

The eastern bank is also the home of the Nepean Rowing Club. Aboriginal people used the river regularly and their fish traps could be seen at Yarramundi before sand and gravel mining redirected the river. Charles Darwin also wrote of people at Emu Fordcommenting on their skill with spears, while Watkin Tench of the Royal Marines also noted their use of spears, lines and nets to capture fish. The people of the Nepean region also regularly traded with people of the western plains via a route that Bell followed when he laid down an alternate route over the mountains, now called Bells Line of Road.

Near Penrith, since numerous Aboriginal stone tools were found in Cranebrook Terraces gravel sediments deposited by the Nepean River 40, to 50, years ago, according to repeated, revised and corroborated radiocarbon and thermoluminescence dating.

If you live or work in the Hawkesbury-Nepean Valley you are at risk of flood

At first when these results were new they were controversial. More recently in and dating of the same sediments strata has revised and corroborated these dates. Karskens et al. Meanwhile, Lieutenant Watkin Tench set off to walk inland, west of Sydney. Nepean river was also one of the pivotal sites of the Hawkesbury and Nepean Warsa series of civil wars between the Kingdom of Great Britain and the resisting Indigenous clans in the late s and early s. During the s, the Nepean district's most famous early settler, the landowner and physician Sir John Jamison —erected a Georgian mansion, called Regentville House, on the model estate which he had established on a rise overlooking the river, not far from the present-day city of Penrith.

A fire devastated the house in the s. Jamison is considered one of early Australia's most important political and agricultural pioneers. Despite forming the effective western and south-western boundary of the metropolitan region of Sydney for its entire length, there are very few fixed crossings of the Nepean River.You may want to upgrade your browser.

We have detected you are using Internet Explorer 10 or earlier. It is recommended that you update your browser to the latest version to get a better user experience. Find out more. This study will provide a better understanding of the potential impacts of floods across most of the city.

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nepean river flood study

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nepean river flood study

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Obtaining approval to build Expand sub menu. Development Certification Expand sub menu.The streams investigated in this study included the Flood behaviour was defined using a computer based hydrologic model of the Upper Nepean catchment and a hydraulic model of the streams. The hydrologic model was based on the RORB runoff routing program and was initially calibrated to recorded rainfall and streamflow data. The records at the gauging stations on the Upper Nepean River were reviewed and flood frequency analyses carried out using a range of annual and partial duration series approaches.

The results are described in Appendix B. Design storms were applied to the RORB model to generate discharge hydrographs within the study area as described in Section 5. These hydrographs constituted the upstream inputs to the hydraulic model. The results of the flood frequency analyses of Appendix B were used to assist with the selection of design RORB model parameters for the major flood events. The largest of the floods available for calibration had a frequency of only 15 years ARI.

A fully dynamic network hydraulic model was adopted for the hydraulic analysis to account for the time varying effects of flows from the tributary streams and the routing effects of the floodplain storage. A one-dimensional link-node model, MIKE 11, was chosen which allowed for the interaction of flows between the channel and the floodplain, flow through culverts and flow over road embankments. This model was calibrated to recorded streamflow and flood level data, as discussed in Section 4.

The hydraulic model was then used to produce water surface profiles and flows in the Upper Nepean River for the design events. The results are described in Section 6. Water surface profiles are shown on Figure 6. Figures 6.

It will flood again

The flood plain storage upstream of Theresa Park Weir, in conjunction with the throttling effects of the gorge between that location and Bents Basin, resulted in a considerable attenuation of the peak discharge, Peak flows at various locations along the valley are shown on Table 6.

Sensitivity studies showed that flood levels between Bents Basin and Wallacia were sometimes influenced by concurrent high water levels in the Warragamba River. The influence of Warragamba River water levels on backwater effects between Bents Basin and Wallacia was more pronounced for minor floods on the Upper Nepean River.

For major Upper Nepean flooding, design levels below Bents Basin were controlled by the constriction between Wallacia and the junction with the Warragamba River, so that the height of Warragamba River water levels had less influence upstream of Wallacia. The results described in this study apply for the long duration storms lasting a few days which are required to maximise floods levels in the Upper Nepean River.

The 48 hour storm was critical for floods up to year ARI. For the PMF, the 12 hour storm was critical in the upper reaches of the model between Menangle and Camden, while the 24 hour storm was critical downstream. It was found that river flooding controlled flood levels for a considerable distance up the tributaries. Local runoff will, however, control flooding near the upper limits of the hydraulic modelling. In order to define peak water levels in those areas it will be necessary to investigate the effects of shorter duration storms.

The models have been set up to allow for more detailed investigations of tributary flooding, although that is outside the scope of the present study. Similarly, the models are capable of modification in future studies to evaluate potential floodplain management strategies and may also be used by Councils to evaluate the effects of development proposals.

Flood study. Report only, no other data. Legacy data; may have been superseded.


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