Temporal Evolution of Basal Force Distributions in Experimental Granular Flows

Granular flows exert fluctuating basal forces that influence erosion, entrainment, and impact‐generated seismic signals, yet the statistical structure and time evolution of these forces remain poorly constrained. Previous studies have primarily analyzed normalized forces scaled by quasi‐static means, leaving the absolute magnitudes and their temporal evolution less explored. Here, we present high‐resolution flume experiments that record raw basal forces during dry granular flows of monodisperse spherical particles. Using a time‐windowed approach, we quantify how force probability distributions evolve through each event and fit each window with a t‐location‐scale distribution to capture heavy tails with finite variance. The distributions typically broaden during the energetic early stage and contract during the decay stage. The location parameter () represents the window‐mean basal force and scales strongly with flow depth, consistent with a simple conceptual decomposition of basal forcing into a static overburden component and a dynamic impact component. The scale parameter () quantifies the absolute fluctuation amplitude and shows a clear positive relationship with bulk flow velocity, whereas its relationship with granular temperature is weaker and more variable across particle‐size groups. The shape parameter () varies intermittently and does not exhibit a consistent dependence on the kinematic metrics resolved here, reflecting the limited force range of our simplified configuration. Preserving raw force magnitudes retains physically interpretable and and provides a quantitative basis for linking basal forcing statistics to impact‐generated seismic observations in granular flows.