Alluvial fan-river systems, which are ubiquitous at mountain fronts, are products of interactions among boulders, pebbles, grains, and the water carrying them. These cross-scale interactions among the granular materials and fluidic environment shape the macroscale self-organized and self-affined alluvial fan-river systems and control the dynamics and evolution of such systems. Theoretical reasoning, and measurements including high-resolution terrane mapping, geophysical probing, geochemical fingerprinting, state-of-art geochronology, and numerical and physical modeling, have been applied to unveil these interactions and quantify the relationship between fluxes, sizes and shapes, as well as the related constants and exponents of scaling laws. In this session, we invite contributions across these disciplines to foster our understanding of how the mechanics, physics, and chemistry at different scales regulate the alluvial fan-river system, which serves as an important habitat for species and reservoirs of nutrients and represents key sediment archives of nearby landscape evolution.