Abstract

Sediment transport in an open unsteady flow with a sharp and smooth change of hydraulic characteristics is studied. Analysis of the experimental results has shown that (I) the response of sediment discharge to sharp changes (increase or decrease) of the hydraulic flow characteristics follows a scheme of a transient process, while in the case of their smooth change (increase or decrease) the response is characterized by a time lag relative to the equilibrium values; the time lag is a function of the intensity of the rise (recession) of a hydrograph and of the absolute magnitude of the mean flow velocity relative to its critical values; (2) under smooth and sharp changes of the hydraulic flow characteristics the regularities of suspended and bottom sediment transport differ considerably; (3) the percentage of suspended particles in the total sediment amount is higher in an unsteady flow than in a steady flow.

Keywords: Sediment transport, suspended sediment, bottom sediment, unsteady flow, time lag