Flood Studies

All levels of government have their own responsibilities in flood preparation and prevention.

For example:

• The Australian Government is responsible for national flood management programs and flood forecasting.
• The Victorian Government is responsible for state flood policy and funding for state flood management programs.
• Local councils regulate development through their planning schemes, co-fund flood studies and manage flood mitigation infrastructure.

Local government authorities (LGA's) handle land use planning and development applications in flood-prone areas and must identify areas at risk of 1% Annual Exceedance Probability (AEP) floods in their planning schemes.

Goulburn Broken Catchment Management Authority (GBCMA) lead the development and implementation of regional floodplain management strategies. They work in consultation with local stakeholders and communities and provide flood advice to municipal councils and landholders. 

Landowners are accountable for flood management on their own property. Local knowledge and experience can play a key role in flood preparation and reduce damage from flooding.

For more information about preparing flood or storm in our area, to stay safe, the hazards of returning home and who to ask for help to recover from a storm or flood emergency visit Floods and Storms.

Flood studies must consider all sources of flooding in the study area, as well as the interactions between them.

To identify this information, hydrologic data (or information related to water resources) is collected such as: 

• precipitation (rainfall or snowfall)
• streamflow
• evaporation
• transpiration
• groundwater
• soil moisture

Available data from past floods is used to create accurate computer models to scientifically investigate flooding in specific areas, often river catchments, to predict where water will go and how deep it might get during modelled flood events.

These models help predict:

• flood flows, levels and speeds
• the chances and impacts (hazards, potential damages) of floods of various sizes
• the likelihood of similar-sized floods happening again
• overall flood risk

The results of flood modelling are then shown on flood maps, illustrating different flooding scenarios, considering factors like terrain, water catchments, historical data and flood marks, to assess the likelihood of floods in the studied area. 

This information guides planning rules and building regulations.

When completing a study, agencies may consult with local communities to take advantage of local knowledge.

This includes capturing resident's experience and knowledge of floods and ensuring Indigenous people's cultural values are considered. 

When assessing new developments or land use changes, LGAs need to:

• determine if the proposed use or development is appropriate given the flood risk and identify the necessary level of flood protection
• evaluate whether the development will increase flood risk for surrounding areas
• seek advice from catchment management authorities and Melbourne Water, who require detailed flood data (extent, depth, and speed) to provide accurate guidance

Flood zones and overlays can affect a property's:

• value
• insurance rates e.g. flood impact premiums
• permit requirements when constructing a building

Governments use flood studies to identify flood-prone areas and regulate development to mitigate risks.

Strategic land use planning can:

• prevent or reduce hazard impacts
• improve community resilience
• save costs compared to other measures

The Planning and Environment Act 1987 supports regulating development in hazardous areas.

By understanding flood-prone zones, authorities can guide residents on how to prepare their emergency plans, including evacuation routes.

For example, the Victoria State Emergency Service (SES) hosts Local Flood Guides for communities to better understand, prepare and respond effecitvley to their flood risk. 

This proactive approach helps communities become more resilient and better equipped to handle potential flood events, ultimately reducing the impact on lives and property.

Access an extensive catalogue of multisource, standardised flood data up to 2018:

• The Australian Flood Risk Information Portal (AFRIP)
• Australian Rainfall and Runoff (ARR)

For an example of a flood study, read the Goulburn and Broken Rivers Flood Study.

Where available, flood risk mapping can assist with planning for floods and can be found on the Digital Twin Victoria platform.

Water Victoria has several documents outlining how flood studies work. 

For more information, you can read: 

• Victorian Floodplain Management Strategy Parts 1 to 5
• Victorian Flood Data and Mapping Guidelines