Grain Sorting Processes

Grain sorting affects river bed aggradation through downstream fining and erosion processes through static and mobile armor formation. A fractionwise sediment transport calculation procedure is presented. It has been calibrated on rotational erosion tests and sediment feeding experiments under equilibrium conditions. In the mobile armor case, equal mobility must be reproduced to simulate the rotational erosion process. Application to flow ranges for which a static armor layer forms shows that transport under equilibrium conditions with identity of subsurface and bedload mixture is then not possible. A unique sediment function exists only for higher flows.