Dealing with cascading multi-hazard risks in national risk assessment: The case of Natech accidents

Natural hazard impacts on industrial activities handling hazardous substances can result in severe cascading events such as fires, explosions, and toxic or radioactive releases. These so-called Natech accidents are often overlooked in regional and national disaster risk management plans. National Risk Assessment (NRA) is a well-known instrument to identify, analyse and compare a wide range of risks with potential impacts at a national extent. Increasingly complex and comprehensive NRAs are used globally for informed decision making. Although recognised as an important emerging issue, Natech risks are currently not considered systematically in NRAs. One cause for this deficiency is the lack of dedicated methodologies and guidance for Natech risk assessment within the NRA context. This study fills this gap by giving insight on how and in which setting Natech risks should be assessed in the NRAs. Following a contextual description of the Natech risk within the overall NRA process, different approaches for Natech risk assessment at the national level are discussed and differences with facility-level risk assessment are indicated. Natech-specific aspects to be considered in risk identification, risk analysis, and risk evaluation are explained in detail with examples from past accidents. Finally, research and policy challenges hampering the reliable Natech risk assessment in the NRAs are discussed. The provided information can improve the coherence and consistency of Natech-related aspects in the NRAs. As Natech risk is regarded as a typical example of multi-hazard risk, guidance on how to consider Natech risk can also support a better assessment of other cascading risks.