Satellite Monitoring of Thermally Active Coal Waste Dumps in the Lower Silesian Coal Basin – Nowa Ruda mine study

Ongoing transformations in the European raw materials sector have accelerated the decline of coal mining and the closure of mines across Europe. This process gives rise to post-mining areas, the environmental impact of which does not end with the end of exploitation. In this context, the ability to predict environmental risks at an early stage, based on analyses carried out on similar sites is crucial. Among the various post-mining features, thermally active coal waste dumps represent a persistent environmental legacy of historical and contemporary coal mining. At these sites, spontaneous combustion and self-heating processes can remain active decades after mine closure as a result of exothermic reactions in coal residues and organic matter. These processes generate long-term thermal anomalies, gas emissions, and progressive degradation of soils and ecosystems. Monitoring such sites is therefore essential for understanding associated risks and tracking long-term changes in thermally active areas, with direct relevance for post-mining land use and reclamation process.

This study presents an Earth Observation (EO)-based approach for acquiring and analysing Land Surface Temperature (LST) to monitor thermally active coal waste dumps and evaluate their relationship with surface and vegetation conditions. The methodology is based on multi-temporal open-access satellite imagery, enabling the detection of both persistent and seasonal thermal anomalies at local scales while supporting long-term environmental analysis at the regional level. The analysis uses Landsat 5, 8, 9 imagery acquired between 1999 and 2025 and focuses on a thermally active coal waste heap near Nowa Ruda in the Lower Silesian Coal Basin (SW Poland), a region transformed by decades of underground coal mining.

Thermal anomalies were mapped and analysed across multiple time steps to assess their spatial patterns and temporal variability. The Self-Heating Intensity Index (SHII) was calculated to quantify the intensity and persistence of thermal activity within post-mining waste materials. LST data were analysed in conjunction with vegetation and surface condition indicators derived from satellite imagery, including NDVI, SAVI, NDMI, NBR and BSI. To understand how thermal patterns and surface condition indicators interact under different moisture and geomorphological conditions at waste dumps, a combination of spatial correlation analyses and seasonal comparisons were used.

The results demonstrate spatial associations between elevated LST values and surface characteristics indicative of limited vegetation cover and exposed substrates, whereas areas with lower thermal signatures correspond to more developed surface cover. Temporal analysis reveals differences in the seasonal behaviour of thermal and spectral indicators, allowing for the differentiation of zones with contrasting thermal and surface conditions.

To address the persistent environmental impacts of coal mining in the context of ongoing transformations in the energy and raw materials sector, this study applies thermal and spectral data obtained from satellites to monitor thermally active mine waste sites. The results can serve as a reference point for risk assessment in other areas undergoing mine closure, as well as providing insight into potentially dangerous phenomena based on experience from areas with a longer history of post-mining transformation.