Stability criterion for a flooded human body under various ground slopes

Extreme flood events often lead to heavy casualties, with flood risk to humans varying with the flow conditions, the body attributes, and the ground slopes. Therefore, it is important to propose an appropriate stability criterion for a flooded human body under various ground slopes. In this study, a formula for the incipient velocity of a flooded human body at toppling instability was derived, based on a mechanics-based analysis. The effect of body buoyancy and the influence of a non-uniform upstream velocity profile acting on the flooded human body under a sloping ground were considered in the formula derivation. 186 tests were conducted in a flume to obtain the conditions of water depth and velocity at instability for a model human body under three ground slopes, with the experimental data being used to calibrate two parameters in the derived formula. Finally, the proposed formula was used to estimate the critical velocities under different depths for real human subjects, in terms of assessing their stability related to floodwaters