Flood Study Update

Storm - Moulder Park - National Avenue Orange - 26 Dec 2010 (Photo - John Kich)

Orange City Council is updating an earlier flood study, which aims to identify areas of potential flooding.

On this site you can :

  • find out more about the study, as well as how and why it was produced
  • learn about the main types of flooding that are being identified
  • look at maps which show the areas of Orange which the study identifies as being potentially affected by flooding.

On this site you can also :

  • find out more about the connections between the flood study and Orange's Planning & Development processes
  • leave a comment, or learn how to make a formal submission
  • ask a question


Orange City Council is updating an earlier flood study, which aims to identify areas of potential flooding.

On this site you can :

  • find out more about the study, as well as how and why it was produced
  • learn about the main types of flooding that are being identified
  • look at maps which show the areas of Orange which the study identifies as being potentially affected by flooding.

On this site you can also :

  • find out more about the connections between the flood study and Orange's Planning & Development processes
  • leave a comment, or learn how to make a formal submission
  • ask a question


CLOSED: This discussion has concluded.

  • A question regarding floor inundation levels. Volume 2 of the flood study identifies houses that it considers to be at risk of above-floor inundation, yet the document itself states that this is based on 'a drive by survey' and that these are 'indicative only'. Is this not an irresponsible action to take? Council is publicly identifying properties as potentially subjected to above-floor inundation during a 1% flood, based on driving past the property. Such significant characterisation will have a major impact on those residents house prices and insurance, based on seemingly little evidence or formal process. I'd also note that surely in such a situation where there is a chance of being affected by overland flow, council bears significant responsibility due to the primary cause of this being stormwater systems that are insufficient. What steps will council take to rectify such systems?

    Neil asked 3 months ago

    Thanks for your question. This Q & A feature is about providing information rather than community debate. If you want to raise concerns about the way the study was completed, the best way forward is to make a formal submission addressing your concerns and/or making a comment online in the comment section. The deadline for submissions in 26 August.

    Here is some further information about the topics you raise.

    Floor inundation : The flood study was conducted according to standard industry practices to produce maps which accurately map the depth of flood levels across the whole of the community. While it was not within the scope of the study to visit every one of more than 16,000 residential properties in Orange to measure individual floor heights, online images were viewed of the streetfront of each property in a flood zone to obtain an indication of floor heights. This is what the term ‘drive-by survey’ means in the context of the study.

    If property owners want to engage a qualified surveyor (at their expense) to measure individual floor heights, that information can be compared with potential flood depths. If this finding changes the way individual properties are listed, the flood study maps can be updated.  

    Stormwater systems: An important reason for conducting the study is to qualify for government funding to continue to work on improving the capacity of stormwater systems. As grants are made available, stormwater systems will be upgraded.


  • In the event that I have to evacuate my property, should I turn off all electricity/gas etc, and will the ses advise me when to leave, and does water flow into my property thru the drains in my bathroom/laundry etc, and where should I go to and what about my pet ( which is a cat)

    elsa asked 3 months ago

    Thanks for your question. Orange City Council's updated flood study looks at the likelihood that areas of Orange will experience flooding after a heavy storm.

    It helps emergency service organisations like the SES plan for which areas may be affected by flooding.

    The topics you ask about are important, but they aren't covered by the study.

    In the event of a flood, emergency services teams like the SES, the Police and NSW Fire & Rescue would communicate about these matters with affected residents.   

  • Q.1. Now that council has improved knowledge on potential flooding in and around Orange, will council be applying for funding for retention basins upstream of these flooding areas to reduce flows? For example at Moulder Park and Ridley Oval to reduce flows in Blackmans Swamp Creek and Orange Creek. Q.2. Will Council be looking at better and/or more stormwater drains in areas where roads currently have inadequate drainage, for example along Williams Street and McLachlan Street, to help prevent water build up in these areas prior to potential flooding?

    asked 3 months ago

    Thanks for your questions. Yes, the study lets the council do the work.

    Q. 1 Yes, the NSW Government requires councils to complete flood studies like this. Producing the detailed information about local needs, is a key step towards qualifying for government grants for a range of mitigation work i.e. projects that are aimed at preventing and/or minimising the impact of flooding. A good example that’s already been built along Blackmans Swamp Creek is the detention basin in Pilcher Park upstream from Moulder Park.

    Q. 2 Yes, in recent years, Orange City Council has been upgrading stormwater channels in along East Orange Creek. By increasing the capacity of the channels, that’s already reduced the impact of flooding on properties in, say, Autumn Street. As the council qualifies for more funding, plans to upgrade the next sections of that channel across McLachlan Street can be implemented.


  • I attended the public forum on 1August and asked what the relevant RL was for the overland flow effected lands and where in the document was it provided. Anyone wishing to develop would need this basic data to prepare appropriate plans. There was no specific answer provided just an indication that the data was accurate to within 30mm and council would have contour mapping. From the general engineering perspective this is possibly suitable however, from a planning and development perspective it is absolutely unacceptable. The proposed DCP and LEP amendments if not stipulating at least a base RL for depicted land should not and must not be adopted inclusive of isolated pockets of overland flow without more detailed and specific mapping of the sites at the expense of Council as onus of proof rather than relying on the LIDAR interpolation which in several circumstances appears anecdotal at best. The potential impact on land owners, land values and the impact on insurability was covered, but glossed over. The Engineering presentation and detail for the overall benefit of risk management and reliable data for funding and grant applications is not disputed and is to be congratulated. The problem with the proposal is the inception of the proposed amendments to the LEP and DCP which will unduly impact land owners and developers with additional onerous justification requirements based on poor mapping. It should be a case of if in doubt leave it out. Will Council be running a similar public forum presenting the planning perspective and implications?

    Wayne McDonald asked 3 months ago

    Thanks for your questions. The answers to these matters are technical and complex.

    The design flood height of Overland flow affected land relative to the existing surface level of the allotment can be derived by using the thermal scale on Sheets 1-7 of Figure 6.6 of the Flood Maps, An appropriate floor height (base RL) for a development can also be given at a pre development meeting. From a planning and development perspective it is quite acceptable and normal with every council within NSW to attend a free of charge pre development meeting prior to the development of Development Application plans.

    Using LiDAR, and the latest 2D flood modelling software, generates extremely high quality flood mapping that is not in doubt.

    The anticipated flood levels are relative to the surface level at any given point, therefore to provide a definitive RL would not be accurate beyond a single point on the map. The current LEP mapping follows the same approach and the LEP and DCP amendments seek only to move the mapping from the LEP where it is time consuming to update, into the DCP where updates can be undertaken more readily, such as when future reviews of the flood study may occur.

    Currently applications for development on unmapped land have to be reviewed internally to determine any risks and appropriate responses. The lack of mapping may therefore cause delays in assessment and additional costs in redesign to address the level of risk. Providing mapping up front alerts developers of the need to seek advice earlier in the design process and thereby reduces costs and delays. We therefore do not agree that the amendments impose any additional burden or constraint on land owners or development.

    At this stage, Council doesn’t intend to run a public forum for planning implications as the DCP was discussed at the forum.

    You are encouraged to come into council and allow the engineers to discuss with you how to read and derive data from the maps.

    As well as asking questions and making comments on line, you may wish to consider making a formal submission to council about these matters.


  • In reassessing flood prone land how will this then impact on property insurance premiums. I like on Ploughmans Creek (Between Sieben Drive & Nicole Drive Orange) and have never seen the water come close to my yard area so do not want Council to jeopardise the insurance coverage by this action

    Coxle asked 3 months ago

    Thank you for your question.

    The flood study has been produced by independent expert consultants, based on industry-standard scientific methods of analysing the movement of floodwater overflowing from a waterway such as Ploughmans Creek in the event of a major storm.

    By completing this flood study at the request of the state government, Orange City Council has only mapped the existing potential flood conditions. It has not added to the risk of flooding.

    The council is not an expert on insurance and any inquiries about premiums should be directed to insurance companies.

    If you wish, a good way to explore these questions further is by arranging to meet a council staff member, or to come to the face to face information session at the Civic Theatre forum on Thursday 1 August at 6pm.