Fluvial Sedimentary Patterns

Geomorphology is concerned with the shaping of Earth's surface. A major contributing mechanism is the interaction of natural fluids with the erodible surface of Earth, which is ultimately responsible for the variety of sedimentary patterns observed in rivers, estuaries, coasts, deserts, and the deep submarine environment. This review focuses on fluvial patterns, both free and forced. Free patterns arise spontaneously from instabilities of the liquid-solid interface in the form of interfacial waves affecting either bed elevation or channel alignment: Their peculiar feature is that they express instabilities of the boundary itself rather than flow instabilities capable of destabilizing the boundary. Forced patterns arise from external hydrologic forcing affecting the boundary conditions of the system. After reviewing the formulation of the problem of morphodynamics, which turns out to have the nature of a free boundary problem, I discuss systematically the hierarchy of patterns observed in river basins at different scales.