Overview
Australia's eastern coastline is home to some of the country's most populous areas and valuable ecosystems, including iconic beaches, estuaries, and coastal wetlands. However, this coastline is increasingly threatened by erosion due to sea level rise, changing storm patterns, and human activities. Monitoring these changes is essential for coastal management, infrastructure protection, and adaptation planning.
Satellite Used
Sentinel-2
Time Period
2017-2023
Challenge
A coalition of coastal management authorities in New South Wales, Australia faced several challenges in monitoring and managing coastal erosion:
- Monitoring over 2,000 kilometers of diverse coastline, including beaches, cliffs, and estuaries
- Detecting and quantifying both gradual erosion and sudden changes from storm events
- Identifying erosion hotspots and prioritizing areas for intervention
- Assessing the effectiveness of existing coastal protection measures
- Developing evidence-based coastal management plans and adaptation strategies
- Limited resources for comprehensive ground-based monitoring
Traditional monitoring approaches, such as beach profiling and aerial surveys, were costly and logistically challenging to implement across such a vast coastline. A more efficient and systematic monitoring approach was needed to support effective coastal management.
Solution
We implemented a comprehensive coastal monitoring system using Sentinel-2 satellite imagery, which offers:
- High spatial resolution (10m) suitable for detailed shoreline mapping
- Frequent revisit time (5 days with Sentinel-2A and 2B combined)
- Multiple spectral bands for water and land feature discrimination
- Consistent and systematic coverage of the entire coastline
Key Components of the Solution:
1. Automated Shoreline Extraction
We developed an advanced shoreline extraction algorithm that:
- Utilized the near-infrared and short-wave infrared bands for optimal land-water boundary detection
- Applied machine learning classification to distinguish between water, wet sand, and dry sand
- Incorporated tidal modeling to normalize shoreline positions to a common tidal datum
- Achieved sub-pixel accuracy through edge refinement techniques
- Processed thousands of Sentinel-2 images to create a time series of shoreline positions
2. Change Detection and Analysis
Using the extracted shoreline data, we:
- Calculated shoreline change rates using linear regression and endpoint rate methods
- Identified erosion hotspots based on change rate thresholds
- Analyzed seasonal patterns and storm-induced changes
- Quantified beach width and area changes over time
- Correlated erosion patterns with wave climate and storm events
3. Coastal Management Dashboard
We developed an interactive dashboard that:
- Visualized shoreline change rates and erosion hotspots
- Provided time-series analysis of beach width at user-selected locations
- Enabled before-and-after comparisons of major storm events
- Integrated with coastal infrastructure and asset databases
- Generated automated reports for coastal management authorities
Visualization of shoreline change rates along a section of the New South Wales coast
Results
Kilometers monitored
Erosion hotspots identified
Cost reduction vs. traditional methods
The implementation of the Sentinel-2 based coastal monitoring system delivered significant benefits:
- Comprehensive Coverage: The system successfully monitored 2,137 kilometers of coastline, providing consistent data across diverse coastal environments.
- Erosion Hotspot Identification: 87 erosion hotspots were identified, with 23 classified as high priority requiring immediate intervention.
- Storm Impact Assessment: The system captured shoreline changes from five major storm events, quantifying erosion volumes and recovery rates.
- Intervention Effectiveness: The monitoring data revealed that some engineered protection measures were performing below expectations, while others showed excellent results.
- Cost Efficiency: The satellite-based approach reduced monitoring costs by approximately 85% compared to traditional survey methods while providing more frequent and comprehensive coverage.
"The Sentinel-2 coastal monitoring system has revolutionized how we manage our coastline. We now have consistent, up-to-date information across our entire jurisdiction, allowing us to make evidence-based decisions about where and how to intervene. The system has already helped us prioritize our limited resources more effectively and demonstrate the impact of our coastal management programs."
Conclusion
This case study demonstrates the powerful capabilities of Sentinel-2 imagery for coastal monitoring and management. By leveraging the high spatial resolution, frequent revisit time, and spectral capabilities of Sentinel-2, we were able to develop a monitoring system that provides comprehensive, consistent, and cost-effective coverage of Australia's eastern coastline.
The insights gained from this monitoring system have directly informed coastal management decisions, including the prioritization of erosion hotspots for intervention, the evaluation of protection measures, and the development of adaptation strategies. The approach developed here can be applied to coastlines worldwide, helping coastal managers address the growing challenges of erosion and sea level rise.