NCCMA, Melbourne Water and Goulburn Broken are the Floodplain Management Authorities by delegation from the Minister responsible for the Water Act 1989.

Consequently, NCCMA is responsible for determining the potential inundation of land from rivers and creeks within the North Central region including Kyneton, Carlsruhe, Tylden, Malmsbury and Lauriston.

Council is responsible for the provision and maintenance of localised drainage and the management of any stormwater overflows from its drainage system.

Flooding is a natural process to all waterways. Flooding occurs periodically due to heavy rainfall within a catchment when storm runoff exceeds the capacity of a waterway’s bed and banks or the local drainage system.

The first stage in managing floodplain risk for a particular catchment involves a flood study, which is a comprehensive technical investigation of flood behaviour for that catchment.

These flood studies show the distribution, extent, levels and velocity of floodwaters across sections of the floodplain for a range of different possible flood events.

Flooding is a significant community issue throughout the whole of our state and country. The average annual cost of damages from flooding in Victoria alone is greater than $100 million.

It is widely accepted that the best way to mitigate against the effects of flooding is through land use planning. Flood studies help us to properly understand flood risk so we can prepare accurate maps, which are used to create flood overlays in the Macedon Ranges Planning Scheme.

The new flood studies represent the best available data to inform planning scheme mapping extents and controls. The existing flood overlay extents are now considered to have a very low or uncertain reliability.

Significant advances in computer technology and industry guidelines mean that the available flood data can be used to more accurately represent catchment conditions and predict flood levels for a range of possible flood events.

A 1 in 100-year ARI* flood is a level of flooding that has a 1% chance of occurring in a given year. It is considered to be a very large flood and is used as the minimum design standard for new development in Victoria.

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. The 1 in 100-year flood is technically referred to as the 1% AEP** flood.

*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 Exceedance 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.

The primary purpose of the studies are to recommend an update to flood overlays within the Macedon Ranges Planning Scheme using advanced flood mapping techniques. The study will improve future land use planning and development decisions to minimise the risks to the community from flooding.

Flood related overlays are a form of flood mitigation. An overlay uses a precautionary approach to reduce potential impacts on people, property, infrastructure and the environment through the appropriate siting and design of development.

The study is not a mitigation plan, but will assist in understanding local flood issues, provide information for future investigations into flood mitigation and assist the prioritisation of works through thorough cost-benefit analysis.

No works are currently proposed as a direct result of this study. However, it will provide information to ensure that future land use planning will be far more effective.

As stated above, NCCMA is generally aware of the extent of flood inundation throughout the Kyneton and Carlsruhe area due to historical information and previous localised 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 Council.

The new information will provide a more accurate picture of a property’s flood risk compared to previous findings. Any effects on land value associated with changes to flood mapping at a given property could only be determined by a thorough analysis alongside other competing market forces. This should be undertaken by appropriately qualified individuals.

A flood overlay is a non-structural flood mitigation tool in the form of a map in the Planning Scheme that shows where land is at risk of flooding. The map corresponds to the relevant planning provisions in the Planning Scheme.

The LSIO is a planning tool applied to land designated as being subject to inundation in the event of a 1% AEP flood. It triggers the need for a planning permit, so that development proposals can be designed in a way that takes flood risk into account.

To find out if your property is either currently in or proposed to be in an area subject to inundation, view the online mapping portal via the link in the 'Updating mapping' section.

The FO is applied to land designated as being subject to inundation in the event of a 1% AEP flood. When a development proposal requires a planning permit approval, the FO ensures that it be designed in a way that takes flood risk into account.

The FO is applied to areas that displays high hazard levels through higher water velocities and greater depth of flooding than the LSIO.

Several factors are considered when development is proposed in areas subject to flooding. Under these overlays, there are buildings and works that do not require a permit.

NCCMA is generally aware of the extent of flood risk. However, the results of the study will provide accurate levels based on the current catchment conditions.

For more information on how to apply for a planning permit under the flood provisions, please contact Council.

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; please contact your insurance provider to discuss any details of your own personal circumstances and insurance policy.

Floodplain management and development assessment is undertaken as part of the planning permit process under the Planning and Environment Act 1987.

Council currently uses the LSIO, and under the proposed changes, the FO to assess development against potential flood risk. Applications are then referred to NCCMA for specialist advice on what development is considered appropriate and any conditions that may apply to the development.

Most new development is required to be constructed 600mm above the applicable flood level which is known as the ‘freeboard requirement’. This ensures that new development is protected from wave action and provides an allowance for changes to flood levels and rainfall information over time as a result of advancements in technology and accuracy.

If the results of the new flood study are different to the existing LSIO extent, development assessed via the planning permit process may still be afforded a high level of protection from flooding due to the freeboard requirements imposed on previous planning permits.

Please contact NCCMA or Council if you have any concerns regarding your individual circumstances.

The Victorian State Emergency Service’s website provides an array of information on preparing for, responding to and recovering from a flood event. Please visit www.ses.vic.gov.au for more information.