Bridge pier scour engendered by typhoons or flooding poses a threat to the stability, bearing capacity, and other performance parameters of bridge foundations. In traditional static evaluation procedures, linear force distributions are used to express the fluid behavior under current forces, which results in overestimation of stability. A finite element simulation was conducted in this study to correctly evaluate the effect of fluid by developing a fluid-solid interaction (FSI) system. In the FSI system, simulation results for both the fluid and solid systems were exchanged. Thus, the force generated by the fluid system could be incorporated into the solid system to estimate the dynamic response of a pier. A scaled single-pier scour test was first conducted numerically and experimentally. The results showed that the established FSI system can consider the fluid-solid interaction and reflect pier scour behavior accurately. To test the validity of the proposed system, the scour process was numerically conducted on an engineering bridge. Two safety factors were proposed to evaluate the stability of the bridge structure under extreme events such as rainfall or typhoon. The result has proven that the scour stability of the bridge pier can be appropriately evaluated by the proposed system.