Abstract: To address challenges in understanding the comprehensive dynamics of dike bend breaches and the hydraulic features during breach evolution, a 3D numerical model is constructed utilizing FLOW-3D software, RNG k-ε turbulence model, and sediment model. The model simulates the gradual breach process in a flume, validated through laboratory tests for accuracy and reliability. Employing this model, the gradual breach of a dike bend is simulated, revealing that the initial breach occurs on the back slope, developing into a V-shape towards the water-facing slope’s toe line. As the breach reaches the foundation, it widens in an inverted trapezoid transverse direction. The analysis extends to the variations in water depth and flow velocity near the breach. Vertically, the highest water depth occurs on both sides of the breach, with a slightly lower and wavy middle; the flow velocity is faster in the middle and slower on the sides. Horizontally, the water depth gradually decreases along the breach flow direction, the water surface line flattens over time, and the maximum flow velocity is observed 50-100 m downstream of the dike. The location of the maximum flow velocity shifts with the breach’s progression over time. The established model enhances our understanding of dike bend breaches and contributes valuable insights into their hydraulic characteristics.