Abstract: To address the trade-off between computational efficiency and simulation fidelity in conventional numerical models, as well as their limitations in resolving discontinuous large deformations and moving boundaries, this study develops a rapid morphological simulation framework for homogeneous levee overtopping breach. A breach model is constructed based on cellular automata theory, incorporating probabilistic water-distribution rules that couple hydraulic-head and topographic-gradient differences. An erosion rule integrating initial spatial heterogeneity and historical-memory feedback is proposed, and the breach-collapse process is determined using a critical slip-surface angle criterion. The model is evaluated against large-scale physical model tests conducted by the Nanjing Hydraulic Research Institute. The model reproduces the main morphological stages, including downstream-toe scour initiation, headcut development, retrogressive erosion and discontinuous collapse, and gives overall agreement with the measured longitudinal profiles. Parametric analysis shows that grid resolution governs the balance between physical fidelity and computational cost; the baseline erosion coefficient controls the global erosion rate; the reduction index characterizes the depth-dependent decay of soil erodibility; and the critical collapse angle controls breach widening. The model is intended as a rapid morphological simulation aid for dam-breach risk assessment and flood-emergency analysis.