What has informed the flood modelling undertaken?
A range of sources and inputs were relied on to inform the model including but not limited to:
- Rainfall, stream flow and climate data from the Bureau of Meteorology, Department of Environment, Energy and Climate Action (DEECA) and other sources which assisted to inform current and future climate scenarios;
- Previous studies, LiDAR and topographic survey data, information provided by community organisations, emergency services, and community members assisted to inform the model calibrations and validations undertaken; and
- Drainage data, details of infrastructure acting as hydraulic structures and controls, land use information, identified Council flood hotspots assisted to inform hydraulic model development, validation and model sensitivity assessments.
Hydrological modelling software RORB was relied on for the hydrological assessment. TUFLOW was relied on for the hydraulic assessment.
Hydrological and hydraulic modelling including model calibration, validation and sensitivity assessments have been undertaken on a catchment scale in accordance with the Australian Rainfall and Runoff Guidelines 2019. Furthermore, the hydrological and hydraulic modelling has been peer reviewed by an industry leading expert.
What is a 1% AEP flood event?
A 1% Annual Exceedance Probability (AEP) flood is a level of flooding that has a 1% chance of occurring in a given year. The 1 in 100 year flood is technically referred to as the 1% AEP* flood. If an area experiences a 1 in 100 year flood in a certain year, it does not mean that another 1 in 100 year flood will not occur for another 99 years, it is an average only. A 1% AEP flood is considered to be a very large flood and is used as the minimum design standard for new development in Victoria.
* Average Recurrence Interval – is the likelihood of occurrence, expressed in terms of the long-term average number of years, between flood events as large or larger than the design flood event. For example, floods with a discharge as large as or larger than the 100 year ARI flood event will occur on average once every 100 years.
*Annual Exceedence Probability – is the likelihood of occurrence of a flood of given size or larger occurring in any one year. AEP is expressed as a percentage (%) risk and may be expressed as a reciprocal of ARI* (Average Recurrence Interval)
Why can’t you include information from the October 2022 flood event in this study?
Flood modelling was completed prior to the October 2022 flood event. It should be noted that the model has been calibrated to the 1993, 2010 and 2011 historical flood events which is considered appropriate for this study.
Why has it taken you this long to come back out to the community with this report?
An initial draft flood study report was presented to Council in October 2020. Since this time, the project has faced delays due to a number of factors including the COVID-19 pandemic and the October 2022 flood event.
What will you do with any feedback provided in this community consultation period?
Information previously provided by community organisations and community members assisted to inform the model calibrations and validations undertaken.
The purpose of this consultation period is to inform the community of the findings and results of the study. Any feedback obtained through this consultation period will help inform any next steps to be taken to support the management of flood risk in Woodend.
What if I can’t make the information session or the drop-in session – can I still ask questions/provide feedback?
Feedback can be provided on the Woodend Flood Study by emailing engineeringservices@mrsc.vic.gov.au or for more information, contact Benup Neupane on (03) 5421 9611.
Will you adopt all the recommendations outlined in the Woodend Flood Study?
Council will take into account all feedback received during the consultation period to help inform the next steps including whether the recommendations detailed within the study will be adopted.
Upon this study being adopted by Council, for any follow-on work recommended to be taken forward this will need to incorporated into future Council plans and budgets. It is possible that external funding may be required to implement this work.
What can I do to be flood prepared?
The Victorian State Emergency Service’s website provides an array of information on preparing for, responding to and recovering from a flood event.
Will the outcomes of the study affect my property value?
As stated above, North Central CMA is generally aware of the extent of flood inundation in Woodend due to historical information and previous flood study findings.
Prior to the completion of this study a prospective buyer of your property could already access information regarding the potential flood risk associated with a property by making the appropriate enquiries to North Central CMA or Macedon Ranges Shire Council. The new information will provide a more accurate analysis of a property’s susceptibility to flooding from a range of flood events compared to previous findings.
Any effects on land value associated with any changes to flood mapping at a given property could only be determined by a thorough analysis in conjunction with other competing market forces. This should be undertaken by appropriately qualified individuals.
Will my insurance premium increase if my property is deemed subject to flooding?
As with any type of insurance cover, a premium is applied for flooding based on an analysis of the flood risk as it applies to your property.
A flood study can assist an insurance company to properly understand the risk posed by flooding to any given property within the study area. This ensures that an appropriate premium is applied to reflect the likelihood of the property being affected by flooding and also ensures that the property is not under-insured.*
*The above statement is intended as advice only; contact your insurance provider to discuss any details of your own personal circumstances and insurance policy.