Accurately simulating the impact characteristics of a dam break is of paramount significance for the prediction and mitigation of dam-break flow disasters. The B-spline material point method (BSMPM), as an improved algorithm of the material point method (MPM), effectively enhances computational accuracy and improves convergence. However, the BSMPM solves the governing equations based on a tensor grid rather than an Eulerian background grid. Moreover, its interpolation shape functions have a larger influence domain. Consequently, when solving problems involving fluid-structure coupling and contact, issues such as premature contact, difficulty in capturing contact interfaces, and challenges in calculating contact forces arise. Within the same tensor grid space of the BSMPM, accurate capture of contact interfaces is achieved based on the relative velocities and unit outward normals of the same nodes; employing the Greville Abscissa enables precise contact of contacting objects, thereby avoiding premature or spurious contact; through the Lagrange multiplier method, interface contact forces are accurately determined, thus constructing a high-precision contact algorithm for fluid-structure strongly coupled problems, facilitating research on the simulation of dam-break fluid impact with rigid and elastic obstacles, and enabling a comparison with existing experimental or simulated results. The results demonstrate that the simulated impact loads and structural deformation evolution patterns correspond well with existing experimental/simulated results. For rigid obstacles, the peak impact pressure exhibits concave parabolic growth and positive correlation exponential function growth with increasing water level and dam-break slope, respectively. For elastic obstacles, the peak impact pressure decreases exponentially with the increase in the height of the probing point. The feasibility and effectiveness of simulating dam-break flow impact problems using the BSMPM contact algorithm are validated, providing a new perspective for simulating dam-break flow impact problems.