Canadian Journal of Civil Engineering 36(10) 1605–16Mathematical modelling of river processes is, nowadays, a key element in river
engineering and planning. River modelling tools should rest on conceptual models
drawn from mechanics of sediment transport, river mechanics, and river
hydrodynamics. The objectives of the present work are (i) to describe conceptual
models of sediment transport, deduced from grain-scale mechanics of sediment
transport and turbulent flow hydrodynamics, and (ii) to present solutions to
specific river morphology problems. The conceptual models described are
applicable to the morphologic evolution of rivers subjected to the transport of
poorly sorted sediment mixtures at low shear stresses and to geomorphic flows
featuring intense sediment transport at high shear stresses. In common, these
applications share the fact that sediment transport and flow resistance depend,
essentially, on grain-scale phenomena. The idealized flow structures are
presented and discussed. Numerical solutions for equilibrium and nonequilibrium
sediment transport are presented and compared with laboratory and field data
