Predicting Bluff Collapses: Using Lidar to Protect Coastal Communities
Understanding Bluff Erosion
Coastal bluffs are steep cliffs found along coastlines, often composed of layers of rock and soil. Over time, these bluffs can erode and collapse due to various factors, including:
- Wave erosion: Crashing waves constantly erode the lower layers of rock, weakening the bluff’s base.
- Rainfall and groundwater seepage: Rainwater and groundwater can seep into the upper layers of soil, making them unstable and prone to collapse.
The Role of Lidar in Predicting Collapses
Lidar (Light Detection and Ranging) is a remote sensing technology that uses lasers to measure the distance between a sensor and the ground. Scientists are using lidar to study bluff erosion and identify vulnerable areas.
Dr. Adam Young and his team at Scripps Institution of Oceanography have developed a new approach to using lidar. They drive along the coast every week, firing a lidar laser at the cliffsides. This high-resolution data allows them to track tiny shifts in the ground, providing early warning of potential collapses.
Predicting Collapse Timeframes
While lidar cannot pinpoint the exact time of a collapse, it can help identify areas that are particularly vulnerable. Geologist Dr. Gary Griggs explains that lidar can predict that a section of cliff will likely collapse within the next 50 years. Future research aims to improve the precision of these predictions.
Coastal Adaptation and Retreat
Coastal erosion is a growing threat due to rising sea levels. Local officials, property owners, and scientists are exploring strategies for adapting to this future.
- Managed retreat: In some areas, erosion will eventually make it too expensive to maintain coastal properties. Communities may need to consider relocating to safer areas.
- Erosion control measures: Traditional methods of coastal protection, such as sea walls and sand replenishment, may not be sufficient in the face of rising sea levels.
- Infrastructure relocation: Critical infrastructure, such as roads, rail lines, and desalination plants, may need to be relocated away from eroding coastal areas.
Balancing Risk and Resilience
Coastal development involves balancing the risks of bluff collapse and erosion with the benefits of living near the ocean. Dr. Griggs emphasizes that “there’s no way to hold back the Pacific Ocean” in the long run.
Communities must decide what level of risk they are willing to accept and develop strategies to adapt to the changing coastal environment. This may involve a combination of managed retreat, erosion control measures, and infrastructure relocation.
Additional Considerations
- Understanding the specific characteristics of rainstorms, waves, and groundwater that contribute to erosion is crucial for predicting bluff collapses.
- The economic impact of bluff collapse is significant, with frequent small storms posing a greater threat than major events.
- Historical approaches to coastal protection, such as armoring, may be ineffective in the face of rising sea levels.
- Balancing the desire for coastal living with the need to protect lives, property, and infrastructure is an ongoing challenge for coastal communities.