FAQ

A number of studies have been completed to date to assist with our understanding of impacts of a levee on the Seymour Township and its surround environment including;

• Economic ‘Benefit Cost Analysis’;
• Flood modelling;
• Ecological Investigation;
• Flora and fauna assessment;
• Cultural heritage Investigations and Management Plan;
• Social impacts;
• Preliminary alignment plans
• Land acquisition investigation;
• Constructability Review.

These reports and studies undertaken by Council provide certainty that the project is viable and that it has significant community benefits.

View an executive summary document of the reports and studies completed to date.

The proposed levee will protect more than 300 individual properties from being inundated during a 1-in-100-year flood event. A 1 in 100 year flood has a 1% chance of occurring in any given year. 

For comparison purposes, the 1974 flood that occurred in Seymour is considered to be approximately equivalent to a 1-in-30-year flood event. This type of flood event has a 3 per cent chance of occurring in any given year.

The protection provided by the levee will reduce the annual average flood damage in Seymour from $1.17 million dollars to $56,000. This is one of the primary benefits of the project.

The levee will also enable a review of the many planning controls relating to flooding for the area that it protects. The review of these planning controls could result in the removal of flood zoning and the flood overlays from some properties which would result in improved development options and increased land values. This increase in land value is estimated to be as much as $2.5 million; an average increase of 20 per cent. 

For people and properties in Seymour that are not directly impacted by the reduction in flood levels, there are a number of indirect benefits. 

These include:

• Reduced disruption to shops and services within the town centre as a result of flooding no longer occurring;
• Improved emergency response and public safety during a flood event;
• Protection of public assets, including roads, schools, parks and recreation facilities; and 
• Increased economic activity and business confidence in the township, both from the direct impact of the levee works and benefits from the possible rezoning of land and improved development options.

The benefit-cost ratio for the works is 2.5 to 1, meaning that for every dollar spent, there is two and half dollars in benefit to the community.

We have examined the impact on the levee on flood levels in Seymour and the surrounding area through the use of detailed computer modelling. The models provide the best indication of the expected flood behaviour after the levee has been constructed.

The modelling found that the levee causes the following flood impacts:

• 1.0m increases in flood levels in the Goulburn River near the connection to the rail embankment of the western edge of Seymour. 
• 0.4m increase in flood levels in the Goulburn River where the levee crosses Emily Street on the Melbourne side of Seymour.
• 0.1m increase in flood levels in the Goulburn River near Robert Street. 
• Near Bolton Street, levels in the Goulburn River are effectively unchanged from the existing conditions
• Downstream of levee, there are minor reductions in flood level in the vicinity of the Whiteheads Creek confluence.
• On Whiteheads Creek, increases in flood level as a result of the levee are no greater than 0.1m with the majority of flood level changes being less than 0.03m. 
• 0.04m (40mm) increase in flood levels in the Whiteheads Creek near High Street. Existing properties in this area are subject to existing flooding conditions.
• No additional properties along Whiteheads Creek will be exposed to inundation as part of this project.

To ensure that all flood impacts are properly identified, we are also currently undertaking a flooding assessment of the entire Whiteheads Creek catchment to better understand the flooding behaviour in the waterway and any impacts on this waterway caused by the levee.

When rainfall occurs over Seymour, the storm water runoff is collected by the existing drainage network of pipes and pits throughout the town and discharged to the Goulburn River.

When the levee is constructed, these pipes that discharge storm water under the levee to the Goulburn River will need to be fitted with special devices, (known as back-flow prevention devices or one way valves) that prevent floodwaters entering these pipes and travelling back up into the town and causing flooding.

If a rainfall event occurs over Seymour when the Goulburn River is in flood, storm water will not be able to discharge freely to the river due to the back-flow prevention devices being activated.  Instead a system of temporary pumps will be deployed across the town to pump storm water out of the underground pipes and over the levee to avoid a build-up of storm water within the town.

Under normal condition when the Goulburn River is not in flood, the storm water will continue to be discharged to the Goulburn River via the existing storm water outfall drains.

During the detailed design phase an analysis of the storm water drainage network throughout the town will be undertaken to determine and performance of the existing drainage network and any improvements that need to be made as part of the levee construction process. This analysis will also confirm the number and size of any temporary pumps that will need to be deployed in a flood event.

The effect on the environment and ecology of the proposed levee was assessed using qualified ecologists. They undertook site investigations and surveys to identify the local flora and fauna that could be impacted by the levee and how any impacts could be minimised. The findings included:

• A Flora and Fauna Guarantee Act permit will be required for the project
• 75 flora species were recorded in the project area; no species of significance were identified
• 50 fauna species were identified; no significant fauna species were recorded
• The project is in proximity to suitable habitat for the growling grass frog. Targeted surveys recorded no instances of the frog during breeding season
• No Flora and Fauna Guarantee Act ecological communities were recorded in the study area
• Some native vegetation will be removed as a result of the project. An offset area that must be protected and replanted with equivalent vegetation will be required

The analysis included a number of mitigation measures that will be included in the design of the levee and recommended actions to occur as part of the construction process. Council is committed to implementing these actions as the project progresses.

Council has commissioned reports that assess the impact of the project on the cultural heritage values and archaeological sites of significance in the vicinity of the proposed works. This includes the development of a Cultural Heritage Management Plan for the works that has been completed with the significant consultation and involvement of representatives from the Taungurung Clans.

The investigations found:

• A number of sites in proximity to the alignment were noted as archeologically significant including a vacant Lot Between Royal hotel and Hanna Street; the Site of the River Goulburn Brewery/Butter Factory (Hanna Street); Seymour Park Pilings; Stone and Brick building on Robert Street; and a Eucalypt at 2 Hanna Street.
• Five areas of Aboriginal Cultural Heritage to be included on the Victorian Aboriginal Heritage Register (VAHR), including three artefact scatters and two low density artefact distributions. 
• The proposed levee cannot be completed in such a way to avoid harm to the five identified VAHR areas.
• The design of the proposed levee can minimise the harm to the VAHR locations
• The report makes specific recommendations for each of the VAHR sites identified to minimise harm. These include construction methods and design considerations.
• Works on the levee, not associated with the key of the levee, are unlikely to disturb artefacts, as the excavation depths are expected to be no more than 0.1 metres.

The analysis included a number of mitigation measures that will be included in the design of the levee and recommended actions to occur as part of the construction process. Council is committed to implementing these actions as the project progresses.

Based on the preliminary design report, a detailed costing and construction methodology has been developed for the project. 

This includes an analysis of the expected construction methods for various aspects of the proposal, the type of equipment used, the project timeline and schedule and estimates of the material quantities for the levee. 

The reports indicate that there are no issues that would prevent construction of the levee, generally in accordance with the preliminary design.

The proposed methodology for the project includes splitting the levee into a number of separate stages, enabling the greatest flexibility in the delivery of the project. The methodology also limits the width required to construct the project, reducing the required area for land acquisition.

The estimated cost of the works is $7.32 million dollars (+/- 25%) as at December 2015.

Where possible, the levee alignment is in public land or on undeveloped land but some land will be required to facilitate appropriate maintenance and ownership of the levee. 

Council will soon commence a process of developing a Planning Scheme Amendment to introduce a Public Acquisition Overlay for land in private ownership that will be required to be purchased for the levee.

Based on the preliminary design, and after a technical review of the available information, the general extent of the Public Acquisition Overlay will be a 30 metre wide corridor along the path of the levee. The land to be acquired includes provision for an access track on the landward side of the levee.

A small number of properties will need to be acquired in full as the levee will block access to these properties and/or cover a significant portion of the property. The exact area of land to be acquired will be finalised as part of the detailed design process of the levee. Council is committed to reducing the area of private land acquired to as small as practically possible. The estimated cost of the land acquisition is approximately $2 million.