The global climate change and the quick urbanization lead to frequent occurrences of flash floods in urban areas;a sliding vehicle in floodwater can impinge against the surrounding infrastructure;and cause damage to the safety of the pedestrians.Therefore,it is necessary to conduct theoretical and experimental studies on the sliding velocity of flooded vehicles,which can provide the scientific reference to urban flood risk management.In the study,all the forces acting on a sliding vehicle in floodwater are investigated, with the corresponding expressions for these forces being presented;and the formulae for calculating the sliding velocity and the maximum impact force are derived,based on the mechanical model for the falling distance of rock riprap and a one-dimensional impact model with the double degrees of freedom. Then a series of flume experiments were therefore conducted using two types of small-scale model vehicles. Finally,the experimental data obtained are used to determine key parameters in the derived formulae;and then these formulae are used to estimate the sliding velocities and the maximum impact forces of the prototype vehicles under various flow conditions.