Abstract: During the implementation of water conservancy and flood control and disaster mitigation, such as river closure and quick closure of earth-rock dike breaches, a strong local scour would occur at the gap or mouth. A 3D numerical model of local scour was verified by the experiments of previous studies, and this model was applied to simulate the local scour around the dike and the riverbed under the one-way and two-way advancement patterns at the gap width B/H = 4.3 and 5.8. The influence of advancement patterns on the development of local scour around dike was analyzed. The results show that in the case of one-way advancement pattern, the gap flow is deflected by the dike to the other side. The local scour of the upstream dike head is always intense in the whole process. Due to the deflection of the dike, the locations of intense scouring downstream are different. The intense scouring area is located at the bottom of the upstream end of the dike at B/H=5.8, and this area is located at the wrapping head downstream at B/H = 4.3. In the case of two-way advancement pattern, the flow is distributed symmetrically along the gap axis. The gap width only affects the intensity of local scouring on the dike. The diving flow and eddy are the main reasons for local scour around the dike.