A methodology for multi-hazard interaction assessment of abandoned mines

The number of abandoned mines is continually increasing around the world. This situation demands that the public safety of surface structures and infrastructure situated above and around abandoned mines be ensured. Abandoned mine sites pose serious risks to people who are unaware of the site's hazards. As a result, post-mining risk assessment and management remain crucial for mining authorities, policymakers, and planners. In the post-mining period, several hazards (ground movement, flooding, gas emission, pollution, etc.) are likely to affect the surface areas above closed mining sites. The effect of closed mines can lead to potentially damaging changes in surface or/and underground water flows, as well as the development of surface instabilities that can pose a grave risk for people, structures and/or infrastructure. This paper presents a methodology for analysing the interactions between hazards around abandoned mines. The methodology was developed based on the assessment of the different hazards that may occur at the mine site, and on the interaction between post-mining hazards and other risks (natural and mining-induced). The methodology provides tools, such as an interaction matrix, and an interaction diagram, that can be used to identify the type and the level of interaction. A multi-hazard index that assesses the level of interaction at a mining site is also proposed, which can be integrated in a hazard mapping tool such as GIS (Geographic Information system) and DSS (Decision Support System). The multi-hazard assessment methodology was applied to a coal mine to demonstrate the complexity but also the utility of such a risk assessment analysis for the risk management of abandoned mines.