The razor in the waterfall: Using longitudinal data to sharpen the analysis of cascading disaster risk

Cascading disasters progress from a triggering disaster event to a diverse range of consequent disasters. Disasters following the Great East Japan Earthquake of 2011 highlight how these cascades also progress to multiple geographical locations. However, the very low frequency of these events means their analysis has usually excluded base-rate data. This common practice risks overestimating future likelihoods. A simplified approach to base-rates for less catastrophic cascades, following the rule of Occam's razor, may help develop more accurate predictions of future likelihoods. The current research hypothesized that an intuitively relevant (0.05) probability of cascading flood-related disasters could be derived from a large, generic register of disaster events. A threshold-based analysis of transitions between phases of a hydrologic flood-related cascade was performed using ten years of data from the USA state of Florida. This analysis identified a 0.05 probability of flood-related cascading disasters. The same analytical methods were reliable when applied to subsequent data, from the year 2000. Similar approaches to information extraction and probability analysis can be applied to climatic data collected at more regular intervals. This will improve the usefulness of analytical results, which can then be added to expert analyses of more contemporary events and scenarios.