Multiphase geophysical flows impacting slit-check dams can create jammed and mobilized domains, which partially govern the overspreading, energy-breaking, and trapping dynamics. This study presents systematic numerical simulations of debris flows, debris avalanches, and rock avalanches against single-slit structures with narrow, medium, and broad openings, using the coupled computational fluid dynamics and discrete element method (CFD-DEM). A typical debris flow is treated as a mixture of discrete particles (by DEM) and a continuous slurry (by CFD). This model well captures essential physics observed in experiments. We show how flow materials, dynamics, and barrier filters alter the impact-induced jammed and mobilized domains that possibly affect the energy-breaking efficiency. Our results reveal that flow materials (wet versus dry) and dynamics (slow versus fast) jointly drive the hazardous overspreading dynamics, while slit openings dominate the trapping patterns, including clogging with domes, blockage, and self-cleaning.