A conceptual model for alluvial fan formation and development

The development of alluvial fans is sensitive to environmental change and, thus, alluvial fans provide essential archives for reconstructing Quaternary paleoenvironmental conditions, particular climate, hydrology, and tectonics. Although alluvial fans have been studied across the globe for over a century, there is no unifying scheme/framework or model to consider their complete variety and mode of formation. By reviewing the global spatial and temporal range of alluvial fan types and data from selected key dryland regions, we are able to develop a conceptual scheme/framework for their geomorphology and formation, and thus aid in their application for Quaternary climate and environmental change studies. This approach suggests that there are three main regimes for alluvial fan geomorphology and formation: Type I) microscale mountain alluvial fans, small in size and extent (radius < a few 100 m); Type II) mesoscale (radius