In developed countries, the majority of fatalities during floods occurs as a consequence of inappropriate high-risk behaviour such as walking or driving in floodwaters. This work addresses pedestrians' instability in floodwaters. It analyses both the contribution of flood and human physical characteristics in the loss of stability highlighting the key role of subject height (submergence) and flow regime. The method consists of a re-analysis of experiments and numerical modelling.

Many flood events have illustrated that the majority of the fatalities during an inundation occurs in a vehicle. So far, only experimental test on small scale cars have been carried out to identify the critical combinations of water depth and velocity causing the onset of motion. A dimensionless approach is here proposed to define a clearer identification of stable and unstable conditions for flooded vehicles.