The erosion-prone area refers to the coastal zone identified as susceptible to coastal erosion and tidal inundation. It is critically important to assess and monitor this zone as it encompasses regions where land loss may significantly impact natural ecosystems and human infrastructure.
Understanding the dynamics of this area is vital for several reasons.
- Ecosystem protection: Coastal ecosystems, such as wetlands and mangroves, play a crucial role in biodiversity and serve as buffers against storm surges. We can implement conservation strategies to protect these vital habitats by identifying erosion-prone areas.
- Risk mitigation: Coastal communities face increasing risks due to climate change, which exacerbates erosion and flooding events. Recognising vulnerable zones allows for the development of effective risk management and adaptation strategies, ensuring the safety of populations and their livelihoods.
- Urban planning and development: Accurate delineation of erosion-prone areas informs urban planning and guides sustainable development practices. It helps policymakers and stakeholders make informed decisions regarding land use, infrastructure investments, and disaster preparedness.
- Scientific research and monitoring: Ongoing research into coastal dynamics is essential for understanding long-term changes and trends. Scientists can better predict future scenarios and enhance resilience against environmental challenges by studying erosion-prone areas.
In summary, identifying and analysing erosion-prone areas is crucial for:
- safeguarding ecosystems
- enhancing community resilience
- guiding sustainable development
- advancing scientific understanding of coastal processes.
Erosion-prone areas have been declared for all coastal local government areas in Queensland. These areas are shown on erosion-prone area plans. Calculation of the erosion-prone areas is based on the following components:
- a sea level rise factor of 0.8 metres
- short-term erosion from extreme storm events
- long-term erosion, where gradual erosion occurs commonly from channel migration or a sediment supply deficit
- dune scarp, where slumping of the scarp face occurs following erosion
- erosion risk due to future sea level rise from climate change by permanent inundation of land by tidal water and the morphological response of the coast to elevated water level
- a 40% safety factor.
The identified erosion-prone area for each Queensland region has not significantly changed since 2016. Notable examples of coastal erosion in recent years include:
- On 2 January 2022, large waves caused by ex-Tropical Cyclone Seth over-washed the dunes on northern Bribie Island and cut a tidal channel through the island. This resulted in the erosion of the Golden Beach foreshore to the west and major impacts on navigation within the passage, including the closing of the Caloundra Bar.
- Woodgate Beach in the Bundaberg local government area, where persistent erosion is threatening roads and other council assets.
- Clifton Beach, north of Cairns, where persistent erosion has narrowed the dunes and put roads and public assets at imminent threat from storm impact. Previous storm impacts have been remediated with beach nourishment but have not lessened the risk of loss due to the continuing erosion of sand along the shoreline.
Mainland beaches and coastlines in the Great Barrier Reef Region
The Great Barrier Reef Outlook Report 2024 assesses the condition of mainland beaches and coastlines as habitats that support species in the Great Barrier Reef Region from Cape York to Bundaberg. The assessment considers various coastal types, including sandy beaches, rocky shores, estuaries, and tidal flats. The following information is drawn from the Great Barrier Reef Outlook Report 2024.
The Great Barrier Reef Region’s coastline is monitored to measure:
- shoreline trends
- erosion and hazard lines
- beach fluctuations
- storm demand (the removal of sand from beaches during storms).
Many factors contribute to the complex equation of whether a particular beach will recede or grow. In general, receding beaches have a deficient supply of coarse sediments, such as sand and shingle. Other beaches build seaward where there is an abundant supply of these sediments from the adjoining nearshore zones.
Understanding of the movement of mainland beaches and coastlines at scale has advanced considerably since 2019 with the availability of new data sources, improved remote sensing techniques, and increased computing power for analysis.
Analysis of satellite images shows that mainland coastlines within the Region have been less stable in the past few years (2019 to 2022) than the long-term average (1988 to 2022), refer to Figure and Table 1. These changes are largely driven by higher recent coastal erosion rates, possibly linked to the influence of La Niña conditions on wave direction. Compared to the long-term average, the most significant coastal changes have occurred within the mainland Townsville–Whitsunday management area.
While most beaches remain resilient, rising sea levels slowly intrude on estuaries and low-gradient shores. This effect is expected to begin affecting beaches in the coming decades and not expected to occur uniformly across the Region. Local changes will likely be further complicated by coastal development and associated changes in freshwater and coarse sediment dynamics.
Non-rocky coastlines remain dynamic. Observed changes over recent years are likely to predominantly reflect natural variation in climatic and oceanic influences, but sea-level rise is expected to increase erosion rates, recession and inundation in coming decades.
Mainland beaches and coastlines from Cape York to Bundaberg remain in good condition.
Observed changes in coastlines in recent years may be the result of natural fluctuations in climatic and oceanic processes. However, these habitats will be particularly vulnerable to projected future sea level rise.
| Shoreline status (% of coastline) | 1988-2022 | 2019-2022 | ||||||
|---|---|---|---|---|---|---|---|---|
| Australia | GBR Mainland | GBR Offshore | GBR Combined | Australia | GBR Mainland | GBR Offshore | GBR Combined | |
|
Stable (<0.31 m/year) | 77.5 | 67.7 | 81.4 | 73.2 | 64.3 | 60.3 | 71.7 | 64.9 |
|
Dynamic (≥0.31 m/year) | 22.5 | 32.3 | 18.6 | 26.8 | 35.7 | 39.7 | 28.3 | 35.1 |
| Eroding | 12.7 | 17.0 | 6.2 | 12.7 | 27.9 | 24.7 | 19.0 | 22.4 |
| Prograding | 9.8 | 15.3 | 12.4 | 14.1 | 7.8 | 15.0 | 9.3 | 12.7 |
This table shows a greater proportion of coastlines were dynamic (predominantly due to erosion) from 2019 to 2022 compared to the full time series (1988 to 2022).
The figure and table are reproduced from the Great Barrier Reef Outlook Report 2024. Source: Analysis by Geoscience Australia using Version 2.1 DEA Coastlines product and following methods described in Bishop-Taylor et al. (2021). Sources: Geoscience Australia 2023, Digital Earth Australia Coastlines v2.1.0. Geoscience Australia, Canberra, and Bishop-Taylor, R., Nanson, R., Sagar, S. and Lymburner, L. 2021, Mapping Australia's dynamic coastline at mean sea level using three decades of Landsat imagery, Remote Sensing of Environment 267: 112734.
Results
See the links below the table for information on the Great Barrier Reef Outlook Report 2024’s full assessment and methods.
