In this study,a numerical model,which can capture the full process of the development of seepage passages,the collapse of dams and the failure due to overtopping,is proposed for earth-rock dams.The critical incipient velocity for the occurrence of seepage failure is derived by analyzing the forces acting on soil particles in the seepage passage.The sediment transport formula is proposed to simulate the erosion process and the evolution of breach within the dam.In this model,the grain size distribution,the compaction density and the strength of dam materials are reasonably accounted for.Furthermore,the influences of the direction of seepage paths,the slope of the dam and the velocity of water flow on the amount of erosion are also taken into consideration.The proposed model and the corresponding numerical programs are employed to simulate the development of breaches and discharge of two typical cases due to seepage failure.The development of breaches,the history of discharge and the peak flood flux predicted by the numerical models are rather comparable to the measured data,which confirms the validity of the proposed model and the feasibility of applying the model in evaluating the disaster consequences and preparing the emergency counter measurements in the case of dam collapse. In this study, a numerical model, which can capture the full process of the development of seepage passages, the collapse of dams and the failure due to overtopping, is proposed for earth-rock dams. Critical incipient velocity for the occurrence of seepage failure is derived by analyzing the forces acting on soil particles in the seepage passage. sediment transport formula is proposed to simulate the erosion process and the evolution of breach within the dam. In this model, the grain size distribution, the compaction density and the strength of dam materials are reasonably accounted for.Furthermore, the influences of the direction of seepage paths, the slope of the dam and the velocity of water flow on the amount of erosion are also taken into consideration.The proposed model and the corresponding numerical programs are employed to simulate the development of breaches and discharge of two typical cases due to seepage failure. development of breaches, the history of discharge and the pea k flood flux predicted by the numerical models are rather comparable to the measured data, which confirms the validity of the proposed model and the feasibility of applying the model in evaluating the disaster consequences and preparing the emergency counter measurements in the case of dam collapse.