Rochester Flood Study 2025 Update

A Flood Study Reference Committee (FSRC) has been established as a local level advisory committee to act as a sounding board in support of the flood study and development of the associated floodplain risk management plan. In summary, its role is to ensure all important aspects of the study are considered, provide a focus for discussion of technical, social, cultural, economic, environmental and ecological issues and provide a link to the community in relation to flood risk and management issues.

Membership is distributed over the Rochester urban and business community, residents and property owners within the broader flood plain between Eppalock and upstream of Echuca and those with an interest in the water resources of Lake Eppalock and the Campaspe River in view of consideration of the lake Eppalock study outcomes as part of potential flood mitigation measures.

The Committee’s inaugural meeting was held on 25 June where it was briefed on its role, the study methodology, program and proposed community communications program. We are also seeking any flood related information members may be able to source from the community. 

Council has actively engaged the community in the Rochester Flood Study, issuing over 2,500 invitations to property owners and residents from Axedale to just south of Echuca. The response was overwhelming, with more than 100 individuals and small groups contributing valuable flood information and photographs during the sessions held on 16 and 17 July. This collective effort has provided a comprehensive range of data spanning the entire floodplain, which is instrumental in refining our flood models.

We encourage the community to continue sharing their insights by uploading photographs here. For those with videos to contribute, please reach out directly for a specialised upload link, as the website has limited capacity for video submissions.

Our team is diligently working on gathering all necessary LiDAR data to cover the area between Lake Eppalock and Echuca, ensuring a thorough topographic survey of the floodplain. Concurrently, we are collecting information on local infrastructure, including bridges, culverts, channels, and drainage structures, to integrate into our hydraulic model. This meticulous process is essential for the accuracy of our flood predictions.

The next steps involve seeking quotations for additional surveys, including the Campaspe River channel and floor level surveys across the floodplain, which will provide a more detailed analysis of Rochester township. These surveys will also incorporate flood marks identified during the community sessions.

Our flood engineers at HARC are compiling hydrological data to develop a comprehensive hydrologic model, which, along with the hydraulic model, will enhance our understanding of rainfall and runoff patterns across the catchment.

We acknowledge the complexity of this endeavour and appreciate the patience of our Community Reference Committee as we work towards presenting the initial modelling results. The upcoming meeting in late October aims to showcase the calibration process using historical events as benchmarks.

For ongoing updates and inquiries, please stay connected with us. Your contributions and engagement are crucial to the success of the Rochester Flood Study.

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A bathymetric survey of the Campaspe River channel between Campaspe Weir and the Waranga Western Channel syphon downstream of Rochester is planned. Property occupiers on the Campaspe River floodplain downstream of Eppalock will be notified within the next week, seeking their cooperation for the survey activities over the next 5-6 months. These activities include:

• Surveying bridges and structures along the Campaspe River, including Campaspe Weir, the syphon, and several extended river cross sections.
• Surveying floodmarks submitted by the community at over 60 properties.
• Conducting floor level surveys of significant buildings on the floodplain downstream of Eppalock to Echuca (approximately 350 buildings plus Rochester Township).
• Performing external building surveys of all residential, commercial, industrial, and community buildings in Rochester (approximately 1600 sites) to prepare cost estimates for flood proofing. Entry into buildings will not be required.

This survey work will be costly and time-consuming. Priority will be given to surveying river structures and flood marks essential for calibrating flood models, followed by floor level and building surveys.

Accurate calibration of the flood models is crucial for the project's success, as all mitigation options need testing in the model to understand their benefits and potential adverse effects. The assessment of mitigation options, including house raising and Eppalock alterations, will follow the development of the flood model and documentation of the river and floodplain's existing behaviour.

The development of both the hydrologic model (streamflows and rainfall inputs) and the hydraulic model (floodplain topographical model) is ongoing. Matching and verifying aerial survey data sets (LiDAR), assessing information from over 100 groups at drop-in sessions, and reviewing and inserting thousands of public authority drainage and bridge structures is proving to be a significant task. The model calibration is scheduled for completion by May 2025. The Community Reference Committee will be consulted as this work progresses and new information becomes available.

We have received numerous flood mitigation suggestions. Until we complete the first stage of the project, which involves developing an accurate flood model and documenting flooding characteristics under standard design events (20% AEP to PMF) and assessing damages, we cannot evaluate the performance and benefits of these suggestions. However, we are documenting all community suggestions for future assessment.

Current suggestions include:

• Operational and infrastructure changes for Lake Eppalock as identified in the Lake Eppalock Technical Assessment Report.
• Levee banks and flow diversion schemes.
• Upstream retarding basins above and below Eppalock.
• House raising, building flood proofing, and individual property flood walls.

Every suggestion will be thoroughly investigated once the project reaches the appropriate stage.

Survey progress and community involvement

In our previous update on 8 November 2024, we shared the progress of our surveyors in collecting flood marks identified by the community, floor levels across the floodplain, Rochester building details, and river structure details including bridges, Campaspe Weir, and the Waranga Western Channel Syphons. We are pleased to announce that the survey work was completed just before Christmas 2024, incorporating many additional flood marks pointed out by the community during the surveyors' site visits. The community's cooperation and support have been greatly appreciated.

Data collection and model calibration

The collected information, along with structure records from VicRoads, Goulburn Murray Water, VicTrack, and Council records, provides the flood engineers (HARC) with most of the data needed to complete the calibration of the hydraulic model. Some minor survey work may still be required to resolve any discrepancies between the flood records and the model's output.

Model calibration progress

The calibration of the model, which ensures it accurately represents the floodplain's behaviour, is progressing well. The model is being calibrated to reproduce the 2011, 2022, and January 2024 flood events based on historical stream flows, rainfall, and floodplain features. Once the community agrees with the results, the model will be used to map flooding behaviour for a range of 'design' flood events, from a 20% chance of exceedance in any year (20% AEP or 5 Year ARI) to less than 0.1% chance of exceedance in any year (greater than 1000 Year ARI).

Upcoming reviews and community involvement

Significant progress has been made with the latest survey information, resolving issues related to long run times and the modelled 2022 event around Rochester. We expect to have accurate modelled results for the 2011, 2022, and January 2024 events along the Campaspe River downstream of Lake Eppalock available for the Community Reference Committee (CRC) to review in early to mid-February 2025. A full public review of the draft calibration mapping will follow, with adjustments made to correct any discrepancies identified by the CRC. This may require further field surveys to accurately identify floodplain features.

Next steps and further updates

The community process is expected to commence around April-May this year. Calibration of the model is the most critical component of the project, as it underpins the study, including the design flood mapping and assessment of various flood mitigation measures. Once the model is calibrated and the design events mapped, we will begin examining all possible mitigation options, expected to start around May-June.

Further updates will be provided as the study progresses. Updates will continue to be added to this page and community members may also register their email address below by clicking the ‘Subscribe to this page’ button to receive notifications whenever the site is updated.

The Community Reference Committee (CRC) have reviewed the initial computer model calibration runs in Rochester. The CRC generally supported the work so far, noting that the modelling is fairly accurate, though some adjustments are needed.

The Project Control Group continues to meet with HARC every three weeks to ensure the study stays on track. The project is currently in the hydraulic model calibration phase, which is crucial for the study's reliability.

• Hydrology (river gauge) calibration for 2011, 2022, and 2024 events is accurate.
• First hydraulic model calibration runs for the 2022 event are complete.
• CRC agrees the hydrology and hydraulic model is producing reasonably accurate inundation maps for 2022 calibration runs.
• Ongoing work to resolve discrepancies identified by the CRC and others.
• Further calibration improvements are being made.

Next steps:

• Update and calibration mapping will be added to the Campaspe Shire website in late February.
• Further CRC briefing in late March with preliminary 1% AEP design mapping.
• Community consultation for feedback on draft final calibration runs and flood mitigation suggestions is schedule for late March/early April.
• Mapping of design flood events will start around mid to late April, following successful calibration.

Consultants HARC continue to adjust and calibrate the hydraulic model to match observations and information provided by the Community Reference Committee (CRC) and field inspections with various landholders along the river upstream of Rochester.

The model is producing generally good matches with recorded flood marks, however there remains room for improvement to achieve better matches within the Rochester township.

Calibration of the hydraulic model is taking slightly longer than initially planned. Its accuracy is critical to understanding the behaviour of the floodplain and for testing the various mitigation works that the community and consultants identify. Investment in the small amount of additional time to ensure it is as accurate as reasonably possible will prove invaluable later in the study.  

The project remains in the hydraulic model calibration phase, with the Project Control Group meeting with HARC every three weeks to keep the project on track.

Next steps:

• Update and calibration mapping is now planned to be added to the Campaspe Shire Council website in early April.
• Further CRC briefing in mid-April with 2011, 2022 and 2024 calibration and preliminary 1% AEP design mapping.
• Community consultation for feedback on draft final calibration runs and flood mitigation suggestions is scheduled for mid to late April.
• Mapping of design flood events will start around mid to late April, following successful calibration.

You can submit your flood marking evidence and photos to the Rochester Flood Study team to assist in calibrating the computerised flood model to make sure it is accurately replicating past events. Please note the Flood Study Team are seeking evidence of flood markings only - not photos of flood damage. The Flood Study team are particularly interested in photographs and flood marks relating to 2011, 2022 and January 2024 flood events.

If you have drone or video footage, complete the form but do not upload the video. A member of our team will be in touch to arrange a copy of the footage from you.

You can submit your flood marking evidence photos by completing and attaching photos to the form below.

Click here to complete.

If you need assistance, please contact us on 1300 666 535 or visit any of our Service Centres or the Recovery Hub in Rochester.