Laboratory Experiments on Human Motion During Urban Floods: Preliminary Results

Current methods for flood risk assessment at urban scale are generally based on three common factors: 1)Site hazard, due to the location of urban areas in risk-prone regions; 2)Built environment vulnerability, including possible floodwater-induced damages; 3)Community exposure, addressed in terms of exposed population (number and characterization) and social-economic factors. The interactions between individuals and the flooded environment are relevant elements for inhabitants’ safety that should be considered in risk assessment evaluations.

Previous works underline how emergency and evacuation choices could lead people to additional hazardous conditions, thus affecting the overall number of casualties. Hence, reliable risk-analysis tools are needed to provide suitable design solutions for resilient cities, in view of the rising number of floods in recent years. To achieve these goals, experimentally-based behavioral investigation are performed using both analysis of real-world event data and laboratory experiments. The main outcome is the development of flood-evacuation models, characterized by feasibility and reduced approximations/simplifications.

Evacuation simulators representing man-man and man-environment interactions could play a key role in a more comprehensive evaluation of individuals’ safety [1]. Although recent efforts in supplying analysis of evacuation behavior allowed to trace different simulation-model schemes, focusing also on qualitative analysis of human reactions in real-world emergencies, experiments for the description of human motion in floodwater conditions need to be investigated in more depth.

The currently limited investigation of the relation between evacuees’ motion speed and flood features has mainly evidenced how stream depth and speed affect the evacuation. Additionally, previous works dealt with human body stability during floods (mainly affecting sliding and toppling) by means of experiments with volunteers, mannequins or using theoretical models.

However, additional investigations are needed to develop more accurate simulation models. To this aim, this work provides preliminary results on the relationship between flood features (water depth and speed) and individual’s motion. Pedestrian’s speed in floodwaters is evaluated by means of experiments in which volunteers have been requested to walk in an artificial channel where flooding conditions are reproduced. Results show that speed differences exist, due to different physical factors (e.g., gender, age, height). Stability loss is tested by exploiting a mannequin representing the human body. Relationships between such factors may be used for the development of evacuation simulators aimed at both assessing critical urban conditions and evaluating the effectiveness of risk-reduction strategies.

[1] Bernardini, G., Postacchini, M., Quagliarini, E., Brocchini, M., Cianca, C., D`Orazio, M. (2017). Environmental Modelling & Software, 96, 14-29.