Creek flood mapping

Properties that are not in creek flood risk area’s may still be vulnerable to overland flooding. It is important to remain aware that flood risks exist beyond what is represented in creek flood maps. For more information about overland flow flooding please visit Stormwater or roofwater drainage.

The covering of normally dry land by water that has escaped or been released from the normal confines of:

• any lake, or any river creek, or other natural watercourse, whether or not altered or modified;
• or any reservoir, canal, or dam.

Flood mapping visually depicts areas that may be prone to flooding under different scenarios. These maps help predict how floodwaters might spread due to various weather conditions. The RCC flood mapping focuses on the different types of storm tide, overland flow and waterway or creek flooding.

This flood mapping shows key waterways of the region and the potential effects of flooding. Creek flooding occurs when heavy rain falls over a creek catchment and causes flood levels to rise in the creek/waterway and overtop the creek banks which results in flooding. Floodwater from the creek can rise quickly and be very fast moving, and then recede quickly.

Flood maps support the following crucial purposes:

• Risk assessment: Understanding flood risk allows individuals and communities to make informed decisions about property, infrastructure, and development. 
• Emergency preparedness: Flood maps help the community, Council, and emergency services plan evacuation routes, identify potential rescue areas, and allocate resources effectively.

The release of flood mapping was a recommendation from the Queensland Flood Commission of Inquiry. This mapping represents the most recent creek mapping data available to Council.

The Commission of Inquiry into the 2010–2011 Queensland floods, was an investigation into the devastating floods that struck Queensland in late 2010 and early 2011. The enquiry played a crucial role in identifying areas for improvement in Queensland's flood management strategy. Its many recommendations included undertaking an update of flood mapping and for Councils and the Queensland Government to publicly share commissioned or adopted mapping with the community.

A flood model is a numerical computer-based model used to create flood mapping. Flood models estimate flood levels from rainfall information sourced from the Bureau of Meteorology (BoM). Key parameters that influence the development of the flood maps include:

• Rainfall and storm event information
• Mapping of land contours, hills, and waterway locations
• Studies of local catchments
• Assessment of various rainfall events and the potential volume of water
• Hydrological assessment of the amount of rainfall expected in modelled events

Flood maps are a valuable tool, but they are not perfect. They represent a predicted outcome and may not account for every eventuality. Factors like extreme weather events or changes in land use can influence actual flooding.

Annual Exceedance Probability (AEP) refers to the probability of a particular flood event occurring in any year. The probability is expressed as a percentage and is determined by undertaking a flood model for a site or area.

A flood event with an 1% AEP is a flood that is calculated to have 1% chance of occurring in any one year.

While the 1% AEP flood event is commonly used for urban planning purposes as the line of acceptable risk to protect people and new buildings, there is always a possibility of rainfall beyond that contemplated by the 1% AEP event that may exceed the defined flood event.

Each flood is different and can have a different impact in different areas. These flood maps present flood risk (i.e., what could happen) in a 1% AEP event. The flood maps are developed using accepted flood studies, current standards, policies and the best modelling and information available at the time.

It is important to note that they do not represent any specific actual flood event that has impacted the city, although historic floods are considered in the flood studies.

The purpose of flood maps is to highlight potential flood risks, helping individuals stay informed, prepared, and make more informed decisions to reduce the future impact of floods on our community.

If you have lived in the area for a long time, you may have experienced or seen different flood events throughout the region and noticed they were considerably different. This is because the size and behaviour of a flood in a particular location will vary depending on many things such as:

• how dry or wet the soil is before it rains
• where the rain falls within the catchment
• how intense the rain is, that is how much the rain falls, and for how long
• if the landform has changed since the last flood for example reduced vegetation from recent flooding, bushfire, or land use.

This is why the historically significant flood events throughout the region for example those which occurred in 2011 and 2022 are different.

This can be due to a number of reasons, which include:

• New development: Since the commencement of the flood mapping studies, there has been significant development in the city. Lots newly developed after the completion of the flood mapping studies will not be captured or portrayed on these maps or reflected in the models.
• Outside of the flood risk map: Your property is situated outside of the flood risk area based on model predictions.
• Additional investigation needed: Your property is outside of the existing extent of the flood mapping studies. Additional investigations of these specific areas are required. Areas suspected of being subject to occasional flooding may need to be further investigated for inclusion in future mapping.

No, flood maps do not indicate increased risk, to properties; it simply provides owners with more detailed information about the risks already present.

No, the maps do not introduce new legal requirements or restrictions on your property. They are for informationpurposes designed to assist with planning and preparation.

The mapping is for awareness only and to highlight a potential area or form of flood risk (creek) in the city. Awareness mapping can be amended and reviewed without the need of a formal City Plan amendment process. Further flood data may be incorporated in the City Plan in the future.

While local and state Governments are responsible for identifying and publishing flood data, property owners need to contact their own property insurer, a private valuer, or real estate agent to determine what effect the flood information may have on their interest in individual properties.

The insurance industry has developed and licensed the National Flood Information Database (NFID) to assist insurers in assessing flood risk for individual properties, in collaboration with state and territory governments.

NFID is an address database containing 13.7 million property addresses, integrated with government flood mapping data to indicate known flood risk levels. Due to commercial licensing agreements between governments and flood risk experts responsible for compiling the flood maps, NFID is not publicly accessible.

Insurers typically utilise NFID to evaluate flood risk for individual properties and determine premiums based on this risk, along with factors such as building type, location, and claims history.

However, insurers retain discretion in determining which criteria to use for assessing flood risk. They may analyse data from various sources, including local government flood maps, historical flood records, terrain data, and insurance claims data.

Insurers assess how often a property is expected to flood, how severe the flooding may be, and how deep the flood can get.

For more information, please refer to the Insurance Council of Australia.

Flood models are based on flood studies conducted in various catchmentareas carried out in different time periods. There could be some gaps in flood data or missing information in the maps because of flood model extent limits. Council is continually working on updating flood models and maps. More updates will be released as the information becomes available.

Due to the rigorous and complex data processes used in designing flood models, individual requests for review or reassessment of individual property flood risk in the mapping cannot be accommodated. However, property owners with specific concerns might consider engaging a Registered Professional Engineer Queensland (RPEQ) to undertake flood analysis specific to their needs.

There are several measures you can take, such as ensuring proper drainage around your property, using water-resistant building materials, and staying informed about flood preparedness guidelines.

Council will periodically update the maps to reflect new data and changing conditions. Updates will be communicated to the community.

In case of a flood, you should follow the emergency response guidelines provided by the Council, which include evacuation routes and safety measures.

Council has emergency response plans in place to assist residents during flood events. Visit our website for more information on available resources and support.

Council is currently working on preparing new flood mapping for overland flow and updating existing mapping to enhance overall flood resilience in our city.