Microscopic characteristics of pedestrian movement in floodwater under varied flow directions and velocities

To investigate pedestrian movement and auxiliary measures in dynamic water, this study conducted wading experiments under different flow velocities and directions. Comparative analyses of walking speed and gait parameters were performed to quantify the effects of hydrodynamic conditions. The results show that water flow strongly influences pedestrian locomotion. Under opposite-directional flow, pedestrians shorten step length, reduce step frequency, and increase lateral sway amplitude, indicating a stability-oriented strategy at the expense of efficiency. Under same-directional flow, water exerts a dual influence: at lower flow velocities, walking speed and step length increase slightly, whereas at higher velocities, pedestrians reduce speed to maintain stability. Wall support alters the force application mode by providing lateral support and friction, enabling coordinated hand–foot movement. It alleviates the degradation of walking speed, step length, and step frequency while reducing lateral sway amplitude by 33%–50% on average. Furthermore, a characteristic flood-force indicator, M, integrating the effects of water depth and flow loading, is introduced to unify the observed movement responses. The results show that M effectively captures the attenuation and regulation of pedestrian movement capacity as instability is approached. These findings provide empirical support for improving flood-safety criteria and evacuation models.