For the basins with debris flow development, its channel terrain exhibits a tortuous shape, which significantly restricts the movement of debris flows and leads to severe erosion effects on the concave bank. Therefore, this study aims to analyze the shear force of debris flows within the bend channel. We established the relationship between the shear force and bend curvature through laboratory experiments. Under the long-term erosion by debris flows, the curvature radius of bends gradually increases, however, when this increasing trend reaches an equilibrium state with the intensity of debris flow discharge, there will be no significant change in curvature radius. In general, the activity pattern and discharges of debris flows would remain relatively stable. Hence, we can infer the magnitude of debris flow discharges from the terrain parameters of the bend channel.