Methodology for Assessing Accident Chains Initiated by Natural Disasters in Cities Based on the Extension Cloud Model

With the rapid pace of urbanization, the occurrence of urban multihazard coupling risks has become increasingly frequent, posing serious threats to urban safety and sustainable development. This study proposes a multihazard coupling risk assessment method based on the extension cloud model. A disaster coupling matrix and classification rules are developed to quantify the mutual feedback effects between different hazards. By integrating risk of hazard-inducing factors, urban exposure, and urban resilience into a three-dimensional indicator system, the analytic hierarchy process, entropy weight method, and game theory are employed to determine indicator weights. These weights are then adjusted according to the coupling effects to enhance the scientific validity of the assessment. Cloud droplet generation and the digital characteristics of the model are used to analyze risk uncertainty, with MATLAB employed to visualize risk levels. A case study in a city in Southwest China demonstrates that the assessment results are consistent with actual disaster events, confirming the model’s effectiveness in quantifying multihazard coupling risks. This method not only overcomes the limitations of traditional single-hazard assessments by incorporating disaster coupling mechanisms and fuzzy evaluation techniques, but also provides practical value for optimizing urban disaster prevention systems and supporting emergency decision-making and resilience building.