Australia Flood Map Update 2021

JBA’s team of flood experts have recently updated JBA’s Australia Flood Map with new data, advanced methods, and the latest science, providing you with the most comprehensive insights for your flood risk assessment.

We’ve been the proud provider of flood maps for Australia since 2014 as part of our global mapping capability, empowering the re/insurance, financial, NGO, charitable and public sectors in flood risk management.

Our mapping is used by several local and state governments in Australia to help in flood risk management and planning. This includes Douglas County Council (Queensland) who use JBA’s maps to assess, prepare and mitigate flood risk for their residents, as well as the South Australian government.

The Attorney-General’s Department of the Government of South Australia (ADG) is very pleased to be working with JBA. JBA’s Australia 30m and 5m flood risk data helps in the decision-making process of our planning applications and is currently being used to amend the ADG’s Flood Hazard Overlay Mapping and related Land Use Planning policy – helping us to identify areas of flood hazard to determine the best land use policies and mapping per area. Beyond this, JBA data is key to our wider efforts towards greater disaster preparedness and response in South Australia.
Martin Pullan, Attorney General’s Department, Government of South Australia

JBA’s Australia Flood Map was the first to offer national coverage for all major flood types at 30m resolution, including modelling of all rivers across the country, with seven regions now available at 5m resolution.

The new 5m remodelling ensures that 56% of the population and the most densely populated areas are now captured by the highest resolution mapping available.

Below, we discuss the new high resolution modelling; latest terrain data; bespoke hydrology; updated defence information; and validation against March 2021 floods used in our newly released mapping.



Flooding is an extremely localised peril – it can affect one property while a neighbouring property is spared. Mapping the hazard, therefore, requires high resolution methods to capture the risk most realistically.

As a result, our specialists have remodelled fluvial (river) and pluvial (surface water) flooding at new 5m resolution for seven regions across the country, including the major urban areas of Adelaide, Brisbane, Cairns, Melbourne, Perth, and Sydney. This enables improved representation of flow paths – especially crucial in densely populated urban areas with lots of infrastructure, to avoid over or underrepresentation of the risk.

Image: 2021 flood map at 5m resolution (left) and previous flood map at 30m resolution (right) for Gold Coast. Flow paths are better defined in the 5m mapping, avoiding over representation of the risk. Source: JBA Risk Management


We are committed to maintaining the latest science and methods in our data to enable the most effective flood risk assessment. This year’s map updates have included new data availability from external partners, enabling us to represent the risk even more comprehensively.

The updates have incorporated new high-resolution terrain data, including new lidar data now covering over 70% of the population. Where this lidar data is not available, we have used new and improved alternative terrain data so 85% of the population is now covered in some form by bare earth terrain data (read more about the differences between terrain data in our blog).

Our sophisticated machine learning methods and technical team meticulously review and clean the terrain data, enabling us to define river channels, narrow urban streets, infrastructure, and topography more clearly at both 5m and 30m resolution.

Image: 5m river flood map (left) and 30m river flood map (right) for Campbelltown, Sydney. New terrain data enables better representation of flow paths. Source: JBA Risk Management

Bespoke Australia hydrology

Our specialists have included new Australia-specific hydrological data from 556 river gauge stations and 30 years of rainfall data to model the country’s risk.

We use the Australian Rainfall Runoff (ARR) model from the Bureau of Meteorology to estimate precipitation levels for return periods of up to 100 years and storm durations of up to 72 hours.

The ARR also provides detailed information about infiltration losses (the amount of water that can be absorbed by the ground), which varies regionally throughout Australia due to factors like climate, terrain and soil type. For example, drier regions in the North may experience more significant run-off due to the ground being unable to absorb extreme rainfall.

We also use bespoke methods for each flood type to account for their unique hydrological characteristics. For example, rainfall totals are generated for different hourly durations to represent storms of different durations.

Shorter, intense storms are likely to cause more flooding in steep sided valleys and smaller river catchments, while longer, slower moving storms will have greater impact in flatter regions.

This new data is incorporated into our hydrological model to enable improved mapping of Australia’s specific risk profile, bespoke to its climate and regional diversity.


Defence information has been updated across the whole of Australia, with a Defended Areas layer demonstrating the mitigating effects of flood defences where present. Alongside this, a new advanced approach has been used to create Defended Areas in urban areas, with users now able to isolate defences relating to a specific section of river to understand the impact of defences in localised areas.

All, some or none of the defence information can be considered when assessing the risk, enabling a different view depending on your risk appetite – for example, turning all defences on would enable a best-case view of risk, whereas turning all the defences off would provide a worst-case view.


In March 2021, much of New South Wales and parts of Queensland experienced significant flooding. In order to assess the accuracy of our updates, JBA’s team of specialists used this new source of data to validate the maps against the observed extents from the March floods.

Image: Observed extents in the March 2021 floods (left) and JBA RP100 river flood map (right). Source: Copernicus Emergency Management Service and JBA Risk Management

Our flood data can be used by re/insurers, mortgage providers, banks, asset managers and other investment organisations to effectively assess the extent and severity of flooding. This enables improved decision-making across property and asset screening, risk selection, underwriting, pricing, portfolio optimisation and funding and investment opportunities. The data can also be used by public bodies for land use planning, disaster preparedness and more.

Image: JBA fluvial flood mapping for Australia

The 5m and 30m resolution mapping is complemented by our Australia Flood Pricing Data and Australia Flood Model, and is part of our wider global flood data capability. For more information on any of our data or bespoke consultancy service, get in touch today.