Sediment transport during flood event: a review

Abstract

Flow unsteadiness in flood events has a significant effect on the structure of the flow field and motion of sediment particles, thereby affecting dispersion of pollutants and river ecology. The aim of the present article was to evaluate state-of-the-art research efforts concerning flow characteristics and sediment transport in unsteady flow condition. The paper is organized in four sections: The first section deals with the unsteady parameters which affect sediment transport. In the second section, the flow characteristics in unsteady open channel flow are presented. Different studies showed that the flow characteristics which affect sediment transport including velocity distribution or shear stress during passage of a hydrograph differ from steady flow condition. In addition, measurements during passage of a hydrograph show that turbulence intensity is generally larger in the rising limb of the hydrograph rather than in the falling limb. This causes the peak of sediment load and pollutants occur during the rising limb of the storm hydrograph. The third and forth sections deal with bed load and suspended load in unsteady flow condition, respectively. Studies show that the methods which are based on steady flow conditions generally underestimate the sediment transport rates in unsteady flows. The larger the unsteadiness, the bigger is the difference. Finally, with considering different findings from previous studies, suggestions are presented for further research.

Glacier Biogeochemistry

“…It is well known that floods in large rivers carry the most sediment on a range of timescales (Karimaee Tabarestani and Zarrati, 2015), but it is less well known that the dilute waters that characterise rivers and glacial runoff at high discharge carry the highest solute fluxes. This is because the proportional increase in discharge is always greater than the proportional decrease in total solute concentration, so that the solute flux (the product of discharge and total solute concentration) increases as discharge increases.…”

Characterization and frequency analysis of flooding solid flow in semi-arid zone: case of Mekerra catchment in the north-west of Algeria

“…The main objective of the solid transport data analysis is to determine the origin of the transported sediments, through the analysis of concentration curves as a function of flow rates (C = f(Q)). Several studies have focused on the study of transport and quantification of solids (Nones 2019;Mrokowska and Rowinski 2019;Di Francesco et al 2016;Tabarestani and Zarrati 2015;Vrolix and Pissart 1990). In Algeria, several researchers have evaluated the sediment transport associated with the floods in the country.…”

Impact of Unsteady Flow Events on Bedload Transport: A Review of Laboratory Experiments

“…Attempts have been made to overcome this difficulty by applying the existing theory of sediment transport in steady flow conditions to unsteady flow problems, e.g., by approximating unsteady flow as a step-wise steady flow. However, this approach has proved to be inadequate in transient flows (dam-break flows, flashfloods) [10]. It is nowadays acknowledged that findings for steady flow cannot be fully transferred to unsteady flow events [11][12][13] and, as such, a branch of research on sediment transport in unsteady flow conditions has been developing rapidly.…”