New criterion for the stability of a human body 1 in floodwaters

(1 State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan 430072, 4 China; E-mail: [email protected], author for correspondence) 5 (2 Hydro-environmental Research Centre, School of Engineering, Cardiff University, Cardiff, CF24 3AA, UK; Email: 6 [email protected]) 7 (3 State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan 430072, 8 China; E-mail: [email protected]) 9 (4 Department of River Engineering, College of Water Resources and Hydroelectric Engineering, Wuhan University, 10 Wuhan 430072, China; E-mail: [email protected]) 11 12 Abstract: Extreme flood events often lead to heavy casualties, with flood risk to humans varying 13 with the flow conditions and the body attributes. Therefore, it is important to propose an appropriate 14 criterion for the stability of a human body in floodwaters in the form of an incipient velocity. In this 15 study, two formulae for the incipient velocity of a human body for sliding and toppling instability 16 were derived, based on a mechanics-based analysis, and with both formulae accounting for the 17 effect of body buoyancy and the influence of a non-uniform upstream velocity profile acting on the 18 human body. More than 50 tests were conducted in a flume to obtain the conditions of water depth 19 and velocity at instability for a model human body, with the experimental data being used to 20 calibrate two parameters in the derived formulae. Finally, the proposed formulae were validated in 21 detail against existing experimental data for real human subjects, with different stability thresholds 22 being obtained for children and adults in terms of assessing their stability related to floodwaters.. 23