Abstract: The invention provides a calculation method for dike breach development process, which relates to the field of flood disaster prevention. In this method, the influence of hydrodynamic on the development rate of the breach is considered, and the unit discharge of the breach is taken as the main parameter. The parameter expression between the hydrodynamic factors and the development process of the breach is established for both lateral widening and vertical downcutting. According to the invention, the whole development process of dike breach can be calculated with only a few parameters, and the main parameter unit discharge can be directly obtained by the discharge formula of broad crested weir. As the calculation incorporating as much physical mechanism as possible and simple calculation procedure, the method has high practicability, good repeatability and scientificity.