Deadly floods and their causal factors: A case-control study in Iran between 2005 and 2018

Flood hazard characteristics play a key role in flood-induced mortality. Therefore, it is crucial to evaluate the associations between these factors and flood fatalities. This case-control study was performed in the flood-prone regions of Iran with recorded flood-induced mortality rates during 2005-2018. In total, 369 subjects completed the survey (123 cases and 246 controls); they were selected from 12 provinces and 30 cities. In this study, descriptive and analytical analyses were carried out to measure flood hazard characteristics. Afterward, the correlation of flood hazard characteristics with flood-induced mortality was measured. According to the descriptive analysis, most deaths occurred in summer, during hours of darkness, in areas with one- and five-year flood return periods, and in floods with short rainfall durations. In addition, the spatial analysis demonstrated that most deaths occurred in flash floods, floods accompanied by bad weather, and floods with floating debris. The results of Chi-square and Fisher's exact test also indicated significant correlations between darkness, flood return periods, flood behavior, floods with floating debris, bad weather, other hazards, and flood discharge with flood-induced mortality. According to the regression analysis, the variables of flood discharge over 500 m3/s, flash floods, nighttime floods, and floods with floating debris increased the risk of flood-induced mortality 3.64, 1.62, 3.34, and 1.06 times, respectively. Although changing flood hazard characteristics seems to be impossible, damages caused by floods can be decreased and the lives of people can be protected through appropriate preventive and managerial solutions, planning, training, promotion of preparedness, and timely warnings.