Flash flood outbursts unexpectedly, and is always responsible for loss of life and excessive damage to infrastructure and the environment. It is a complex nonlinear process and the key scientific problem in the hydrology and hydrodynamics. Enhanced knowledge about generation and evolution processes of flash floods is important for effective flood risk management. Flash flood commonly occurs in mountainous and hilly areas in which gauged data is often rare or simply unavailable. Full hydrodynamic modelling incorporates more physical mechanisms, which can describe the details of flows over irregular terrain and reduces the uncertainty of prediction. And thus the need for historical hydrology information is decreased. In this paper, 1) advantages and disadvantages of both hydrological and hydrodynamic models are discussed, 2) key aspects of hydrodynamic model for overland flows are presented, especially for the bed and friction source terms, 3) impact of rainfall, infiltration, friction on overland flows and its determination approaches are reviewed, and 4) the further development directions of this kind of models are proposed