Gravitational mass movements like debris and mud flows are responsible for fatalities and economic losses worldwide. Enhancing our understanding and modeling of such processes is thus crucial for effective risk management strategies. When debris and mud flows run through a curved channel, a difference in flow height, between the inner and outer bank of the channel, may emerge due to centrifugal effects. This flow height difference is called superelevation height. The superelevation can be described by analytical models, which link the superelevation height to the flow velocity. Analytical models often rely on a forced vortex approach, depending on parameters such as the cross-sectional slope of the flow surface, flow width and bend radius. These current approaches rely on an empirically determined correction factor within the formula. However, the lack of a clear mechanical rationale poses challenges in estimating this correction factor. This study introduces an enhancement to the existing forced vortex approach, leveraging numerical modeling results. An SPH-DEM coupled numerical model is used, where DEM particles represent coarse solid particles and SPH accounts for the fluid phase, composed of fines and water. Results from a parametric test underline a correlation between water content and the flow surface shape in curved channels. Specifically, mud flows exhibit convex upward surface shapes, while more granular debris flows tend to display concave downward shapes. The distribution of material within the cross-section of the flow is regulated by the equilibrium between the boundary and centrifugal forces acting on the flow, and hence it directly influences the superelevation. Based on the flow cross-section, we derive a material-dependent correction factor, which is significantly affected by the water content. This mechanical factor demonstrates distinct trends for mud and debris flows. This allows a more accurate back-calculation of debris flow velocities in curved sections marked by mud deposits.