Assessing Wildfire-Induced Changes in Rock Slopes Using Field Observations and Satellite Data

Wildfires initiate a hazard chain that significantly alters landscapes and geohydrological processes. In addition to the extensively documented effects on vegetation, soil erosion, and debris flows, steep and rocky terrains may experience delayed yet persistent slope instabilities. However, post-wildfire hazard assessment frameworks still predominantly use the soil burn severity indicators for any type of mass wasting processes, while the response of rock masses and their contribution to post-fire hazards remain underrepresented.
This study addresses this gap by proposing an integrated, rapid assessment approach to evaluate post-wildfire rock slope instability. The motivation of this study is the necessity of cost-effective and timely tools that support emergency response and short- to medium-term risk management in mountainous Mediterranean environments where infrastructure, settlements, and transportation corridors are exposed to post-fire hazards.
The proposed methodology combines Sentinel-2 Level-2A multispectral imagery with field-based observations. Burn severity was mapped using the differenced Normalized Burn Ratio (dNBR), and field surveys were conducted to validate spectral classifications and to identify fire-induced rock degradation indicators. In contrast to conventional soil burn severity observations, special attention was given to rock-specific responses. The rock burn severity indicators were semi-quantitatively evaluated and integrated within a GIS-based framework to identify potential slope sectors with increased rockfall susceptibility.
Results show that wildfire-induced thermal alteration can significantly weaken carbonate rock surfaces and discontinuities without necessarily leading to rapid slope failures. Wildfire functions as a conditioning mechanism that elevates the susceptibility of rock slopes to subsequent triggers, including rainfall infiltration, runoff concentration, and solar radiation cycles. 
The study emphasizes the importance of incorporating rock-specific burn severity indicators into post-wildfire rock slope stability assessments. Such an approach supports more comprehensive risk inventories and improves prioritization of mitigation and monitoring strategies. The findings contribute to ongoing efforts to integrate field observations and remote sensing.