Using Discrete Element Method (DEM) simulations we show that the trapping efficiency and pile-up geometries of consecutive granular flows, or surges, depend on the flowing conditions, slit opening, and on the number of surges. Flows are characterized by the Froude number Fr and the dam geometry is defined by the ratio of the slit size with the particle diameter b/d. We find that as Fr and b/d are increased, the total and single surge trapping efficiency decreases but only until a threshold value, beyond which it is independent of it. When both Fr and b/d are low, previous deposition prevent subsequent flow from interacting with the slit dam and contribute to more trapping. Conversely, when both Fr and b/d are high, subsequent flow cleans out the previous deposition, resulting in reduced trapping. We show that the pile-up length and height depend on b/d and Fr through the trapping that they induce, although the sensitivity to the trapping efficiency diminishes with the number of surges. These insights contribute to optimizing slit dam design.