Flood

What is a flood?

To put simply flooding is water where it is not wanted.

In November 2011, the Australian Government introduced a standard definition of flood for certain insurance policies. For this purpose a flood is defined as:

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.

Floods can have both positive and negative impacts. They can bring welcome relief for people and ecosystems suffering from prolonged drought, but also are estimated to be the most costly natural disaster in Australia.

Why do floods occur?

Flooding occurs most commonly from heavy rainfall when natural watercourses do not have the capacity to carry excess water. However, floods are not always caused by heavy rainfall. In coastal areas, water inundation can be caused by a storm surge as a result of a tropical cyclone, a tsunami or a high tide coinciding with higher than normal river levels. If a dam fails, triggered for example by an earthquake, the downstream area will flood, even in dry weather conditions.

Other factors which can contribute to flooding include:

  • volume, spatial distribution, intensity and duration of rainfall over a catchment
  • the capacity of the watercourse or stream network to carry runoff
  • catchment and weather conditions before rainfall
  • ground cover
  • topography
  • tidal influences.

Where do floods occur in Australia?

Riverine flooding occurs in relatively low-lying areas adjacent to streams and rivers. In the extensive flat inland regions of Australia, floods may spread over thousands of square kilometres and last several weeks, with flood warnings sometimes issued months in advance. In the mountain and coastal regions of Australia, flooding can happen rapidly with a warning of only a few hours in some cases.

The Great Dividing Range which extends along the length of eastern Australia provides a natural separation between the longer and slower westerly flowing rivers and the shorter, faster easterly flowing coastal rivers. In some cases, natural blockages at river mouths, including storm surge and high tides, can also cause localised flooding of estuaries and coastal lake systems.

Flash flooding, otherwise known as overland flooding, can occur almost anywhere there is a relatively short, intense burst of rainfall such as during a thunderstorm. As a result, the drainage system has insufficient capacity or time to cope with the downpour. Although flash floods are generally localised, they pose a significant threat because of their unpredictability and normally short duration.

Just because an area has not flooded in the past, does not mean it will not flood in future. Similarly, just because an area flooded during one event, does not mean that it will necessarily flood during the next one.

The Bureau of Meteorology maintains the Australia Rainfall and River Conditions which contains up-to-date rainfall and river information for all catchments within Australia.

Talking about floods

The use of consistent terminology is important for improving the quality and consistency of flood information. Geoscience Australia uses the following flood related terms when talking about floods and flood research.

The most costly summer for floods in Australia was 2010-11, with extensive flooding in the Lockyer Valley, Ipswich and Brisbane in January 2011. This flooding resulted in a cost of A$6.64 billion (2013 Australian dollars, including deaths and injuries but excluding most indirect losses). There were 35 deaths and 20,000 people were made homeless. Between 1967 and 2013, the average direct annual cost of flooding has been estimated at A$943 million (excluding the cost of deaths and injuries).

References:

Ladds M, Keating A, Handmer J and Magee L (2017) How much do disasters cost? A comparison of disaster cost estimates in Australia. International J of DRR. 10.1016/j.ijdrr.2017.01.004

Ladds, MA, Magee, L, Handmer, J (2015) AUS:DIS - Database of losses from disasters in Australia 1967-2013. https://github.com/liammagee/sealand

John Handmer, Monique Ladds and Liam Magee (December 2016), Disaster losses from natural hazards in Australia, 1967-2013. (Report with AGD)

What is Geoscience Australia's role in reducing risk to Australians from flood?

Geoscience Australia is committed to support Australia's capability to managing the impact of natural hazards, including flood. Geoscience Australia:

  • develops an understanding of natural hazards and community exposure to support risk mitigation and community resilience
  • provides authoritative, independent information and advice to the Australian Government and other stakeholders to support risk mitigation and community resilience
  • maintains and improves systems for effective natural disaster preparedness, response and recovery
  • contributes to Australia's overseas development program.

In particular, Geoscience Australia:

  • provides a central access point for stakeholders to share flood information through the Australian Flood Risk Information Portal
  • provides the national access point for public good satellite data, which enables Geoscience Australia to provide satellite imagery and derived flood extent products
  • supports Emergency Management Australia to understand what is exposed to floods before, during and after events
  • develops national-scale datasets that supports the understanding of flood hazard and risk
  • supports national efforts to reduce the risk of flood, for example through participation in the National Flood Risk Advisory Group
  • increases the national flood guidance available to support the development of consistent and robust flood studies and risk assessments through mechanisms such as the revision of Australian Rainfall and Runoff
  • collaborates nationally to enhance flood hazard, impact and risk tools and models
  • conducts post-disaster surveys to understand how flood impacts the built environment
  • develops vulnerability models for assessing flood damage
  • undertakes research into household resilience to flood.

The Australian Flood Risk Information Portal (the portal) enables flood information, currently held by different sources, to be accessible from a single online location. The portal includes a database of flood study information and metadata (the Australian Flood Studies Database). The portal provides access to authoritative flood maps and flood studies, as well as information about surface water observations derived from the analysis of satellite imagery.

The portal incorporates tools that enable users to search, display and retrieve information. The data management tools and standards that have been developed for the portal will enable data custodians to standardise their data and upload it to the portal, or to make compliant data accessible via web services.

The information in the portal has been provided by local, state and territories governments. Contributing more flood studies will significantly enhance its value. It will improve our understanding of flood behaviour on a regional scale, which is essential because floods do not respect jurisdictional boundaries.

Share Flood Study Data

The Australian Flood Risk Information Portal (the portal) hosts data and tools that allow public discovery, visualisation and retrieval of flood studies, flood maps, satellite derived water observations and other related information from a central location.

The portal is focussed on providing access to flood information from authoritative sources. The main catalogue of information available through the portal is the Australian Flood Studies Database.

Information in the portal can be searched and accessed by all users, but only registered users can add flood studies and associated maps to the database. A registered user would typically have been responsible for the creation or publication of flood hazard information, and might include state authorities, local councils, consultants and authorised data custodians.

Data custodians can share their flood study information with other users either by adding data directly into the portal's data catalogue, the Australian Flood Studies Database, or via web services.

Data Entry
Information on entering data into the portal, including how to login or register to use the Data Entry Application and links to data entry and quality assurance guidelines.

Portal Framework
Describes the overarching approach taken in developing the portal, as well as the agreed principles and benefits supporting the portal.

Web Services User Guide
A guide to the public web services that support discovery, search and retrieval of flood information from the portal.

Already a registered user?

Data Entry Application

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Frequently Asked Questions

Why was the portal developed?

Following the devastating floods across Eastern Australia in 2011, the Australian Government initiated the Natural Disaster Insurance Review. This review highlighted the lack of consistency across the country in the way flood risk information was collected and made available to users. The review also recognised the need for consumers to be aware of the natural disaster risks they may face, as well as the benefits of making flood risk information more readily accessible.

In response to these findings, the Government established the National Flood Risk Information Project (NFRIP) with the aim of improving the quality, availability and accessibility of flood information across Australia and, in doing so, raise community awareness of flood risks. This four year project commenced on 1 July 2012 and delivered three products; the portal, Water Observations from Space and the Australian Rainfall and Runoff Guidelines. NFRIP supports the objectives of the National Strategy for Disaster Resilience (NSDR) adopted by Council of Australian Governments (COAG) in 2011; specifically, that Governments have effective arrangements in place to inform people about hazard and risk.

Who uses the portal?

The portal is used by engineers, insurers and planners to find out what flood mapping information exists, and where, so they can better understand risks. Researchers and consultants can learn what work has already occurred in their area of interest and identify what data may be available for use in future studies. Organisations can refine the scope of planned flood studies by understanding and applying lessons learnt from work undertaken in other regions. Others in the community can also use it to find out what flood information exists for the area that they live in.

What is a flood study?

A flood study is the scientific investigation of flooding in a particular area, usually the catchment of a river system. It may involve hydrologic and hydraulic investigations and a statistical analysis of the frequency with which floods have occurred. The purpose of a flood study is to predict the depth of water and the extent to which it will inundate the landscape in a modelled flood event.

What is a flood map?

A flood map is the result of hydrologic and hydraulic analysis by scientific subject matter experts, that takes into account many factors when developing models for various scenarios. Such factors might include: terrain, water catchments, flood marks and information from historical floods. A map can represent the extent of a flood, the probability of that event occurring and sometimes the depth of inundation in the modelled area.

Where are flood maps available?

Flood maps can be found by searching the Australian Flood Risk Information Portal (AFRIP). While some flood studies don't include separate mapping data, maps relevant to the specific study can be found in many of the attached flood study documents.

What is the Australian Flood Studies Database?

The Australian Flood Studies Database (AFSD) is the national data catalogue of flood study information that underpins the portal. The AFSD contains general information for available studies, including the study location, date, commissioning organisation and lead consultant, and metadata on flood studies and information on flood risk. The metadata is created through a purpose-built data entry application, and adheres to the Flood Studies Data Model XML schema which can be used by data custodians to structure and share their flood information with the portal via webservices.

How do I search the portal?

You can search for studies and maps by:

  1. selecting an Area on the Map
  2. an address search
  3. specifying your search parameters.

How do I access the actual report and maps?

Where available, these can be downloaded directly from the Details section in the Australian Flood Risk Information Portal once you have identified a study you are interested in. If the study you're interested in has no downloads, you will need to contact the commissioning organisation identified in the study record to determine if a copy of the report is available.

Has a flood warning alert been issued for my area?

Please check the Bureau of Meteorology - National Warnings Summary for details on flood warnings. The Australian Flood Risk Information Portal does not hold information on flood warnings.

What do I do in the event of a flood?

Contact your local State Emergency Services if you require assistance in the event of a flood. The Australian Flood Risk Information Portal is not a response tool.

Can I use or reproduce the information here?

The portal is maintained by Geoscience Australia. Unless otherwise noted, all information is available for re-use under Creative  Commons 4.0 By Attribution (CC-BY) licensing. The ownership of each flood study remains with the commissioning organisation and/or author as indicated in the record on each study. Users of the database should refer to each specific flood study report to determine any constraints in its usage.

What if the database doesn't do what I need it to do?

Your feedback is input to the continued development of the database and the portal. Please share your feedback via the portal's feedback button.

What if information in the portal is incorrect?

Some of the flood studies contained in the database may be incomplete or may have been superseded by new material. Issues with the accuracy of the study itself should be referred to the commissioning organisation, typically a local council or state government agency. However, where incorrect information is displayed in the portal about a flood study, please share your feedback via the portal's feedback button.

Can I add a flood study or flood maps to the portal?

Registered data custodians can add flood studies and maps to the portal. Please notify Geoscience Australia via the portal's feedback button of any other published flood studies that aren't currently included in the database, but may be suitable for release through the portal.

Water Observations from Space (WOfS) is a web service displaying historical surface water observations derived from satellite imagery for all of Australia from 1987 to present day. WOfS aims is to allow better understanding of where water is usually present; where it is seldom observed; and where inundation of the surface has been occasionally observed by satellite. WOfS displays the detected surface water from the Australia-wide Landsat 5 and Landsat 7 satellite imagery archive.

For each grid cell within the map, WOfS displays:

  • the number of clear satellite observations over the period (1987 to present)
  • the number of occasions water was detected
  • the percentage of clear observations on which water was detected, and
  • the confidence (or probability) that a water observation in this location is correct. This is a percentage, based on a number of factors including the slope of the land and the existence of other corroborative evidence.

The WOfS project began in 2011 and included staged releases of information and a trial product. The development of this product is now complete. Data will continue to be updated every three months.

WOfS uses the Datacube application at the National Computational Infrastructure for the storage , organisation and analysis of satellite data.

More information on Geoscience Australia's Water Observations from Space product is available in the WOfS FAQs.

View Water Observations from Space

Use the Water Observations from Space application to view surface water observed by the Landsat 5 and Landsat 7 satellites for all of Australia from 1987 to present.

About WOfS

Find out more about the WOfS product, how it was developed and its role in the broader flood mapping toolkit. For a detailed technical description of the product, see the Water Observations from Space Product Description.

WOfS FAQs

Answer your questions about the WOfS product, how Geoscience Australia is using satellites to observe surface water, and the uses and limitations of the product.

WOfS Help

Learn how to use the WOfS tool and find out more about how to better understand your search results.

WOfS Access Details

Information on how to access the WOfS web services for use in Geographic Information System (GIS) packages.