In this study, we developed and evaluated a new countermeasure construction method through experiments and analysis in anticipation of water permeability through gaps between the interlocking blocks used to construct block sabo dams. In the water channel experiment, deformation of a non‐permeable sabo dam model occurred due to significant overflow and water pressure, such that its trapping function could not be maintained, whereas a block sabo dam model with permeable walls maintained its trapping function even after it was filled with sand. We applied an existing analytical model to explore this novel sediment trapping effect due to sabo dam drainage. The results of our simple model experiments based on ideal conditions suggested that a bottom drain filter would effectively capture debris flow as it passed through the unsaturated sedimentation surface; block sabo dams require further study to ensure their effective development.