Sodic alluvial soils in the Normanby Catchment on southern Cape York are a very substantial erosion source to sediment loads in the Great Barrier Reef lagoon.

South Endeavour Trust acquired three properties (Kings Plains, South Endeavour and Alkoomie Stations) for erosion control and biodiversity protection. The adjacent downstream Normanby Station owned by Balnggarrawarra Indigenous Traditional Owners (Normanby Aboriginal Corporation) is also trying to control gully erosion to protect cultural sites and biodiversity, and are interested in improved monitoring. Furthermore, the Queensland Government has purchased the upstream Springvale Station to specifically reduce gully and soil erosion.

Together, they are all making a substantial private and public investment alongside the Australian Government’s Reef Trust program to control gully erosion and reducing sediment output.

Erosion Monitoring

Accurately monitoring erosion reduction over time over complex areas is the key challenge to the project. Historically, airborne LiDAR (plane mounted) without ground control was used to develop digital elevation models on the property and spatially quantifying changes in erosion gullies. However the horizontal DTM resolution (1m²) and vertical accuracy (±30cm) was not adequate enough to measure detailed changes within individual complex gullies.

In 2016, Mangoesmapping joined with South Endeavour Trust to trial the use of UAVs to gather more dense elevation data in 3 dimensional models derived from high resolution photogrammetry.

The benefit of using UAVs to assess elevation and cut/fill on erosion gullies quickly became apparent. However so too did the need for quality control for new datasets to provide improved spatial accuracy and allow for longitudinal analysis and assessment against existing aerial LiDAR datasets and future UAV datasets.

Approach

Mangoesmapping deployed DJI UAVs (drones) and Emlid GNSS technology to monitor erosion sites on Normanby and Kings Plains Stations. This allowed them to closely observe the outcomes of sediment and erosion control strategies. The data collected from these experiments provided valuable insights into effective management techniques for gully and streambank erosion treatments.

After flying the site, the series of photographs were used to create Digital Elevation Models (DEM’s) for different erosion areas.

Gully erosion on Kings Plains, with digital elevation model (DEM) overlay.

Impact

By monitoring over time, different erosion control approaches could be evaluated. In some areas – Porous Check Dams (PCD’s) were established.

Data could be collected and compared over time to evaluate the effectiveness of the strategies.

Through this monitoring project, Mangoesmapping contributed to the advancement of knowledge in erosion treatment management. Their approach provided detailed information on the relative success of different experimental strategies, enabling better decision-making for conservation efforts.

By enhancing the understanding of best practices, Mangoesmapping significantly contributed to the protection and preservation of the Great Barrier Reef.

3D calculation, showing ~103,000m3 of sediment loss from a Kings Plain erosion gully.

Conclusion

Erosion monitoring using emerging spatial technologies represents a significant breakthrough for the Great Barrier Reef’s preservation.

As the Reef 2050 Plan progresses, these contributions are expected to play a critical role in ensuring the survival of the Great Barrier Reef for years to come.