Computational Modelling of Small-Scale River Morphodynamics

Alluvial open channel beds often exhibit statistically periodic irregularities known as dunes. Dunes have considerable effects on sediment transport and flow resistance. When growing during a flood, the dunes creat more resistance and flood levels may rise significantly. Accurate prediction of dunes properties therefore contribute to effective flood risk management. This monograph concentrates on detailed simulation of flow, sediment transport and bedform morphodynamics. This is achieved by implementing a detailed three-dimensional numerical model for hydrodynamics, sediment transport and morphodynamics. The time-dependent water flow has been simulates by Large Eddy Simulation on a locally refined Cartesian grid. The sediment is considered as rigid spherical particles moving in the water under gravity and flow-induced forces. The bed morphodynamics is the net result of pick-up and deposition of sediment on each portion of the bed. The model is validated against theoretical and experimental results of previous studies published in the literature. The insights and data obtained with this model were used to develope parametric relations that can be used operationally at larger scales