Pedestrian hazard criteria for flooded urban areas

Urban floods are sudden phenomena normally characterized by short flooding durations and devastating effects due to the high concentrations of persons, goods, and properties located in urban areas. In these cases, uncontrolled runoff can flow on urban streets, creating a significant hazard for pedestrians and vehicles. The safety of people can be compromised when they are exposed to flows that exceed their ability to remain standing or to traverse flow paths. With the aim of studying the stability of pedestrians in flooded street during storm events, a model representing an urban street in real scale was designed and built. Following a specific protocol that considering several flow rates (up to 500 l/s) and different longitudinal slopes (up to 10 %), 834 tests, using 23 human subjects, were carried out in good and poor light conditions. Hazard conditions were classified into three groups (low, medium, and high), and the parameters for which these conditions occurred were recorded. Results showed that for subjects weighing 50-60 daN (50-60 kg mass) and flow depths between 9 and 16 cm, velocities of 1.5-2 m/s can generate loss of stability due to phenomena of dragging or overturning. Empirical expressions were proposed to relate human subject characteristics (weight and height) and limiting flow conditions at which loss of stability occurs.