Modelling of Sediment Exchange between Suspended-Load and Bed Material in the Middle and Lower Yellow River, China

Zhao Zhao,Jiang Jiang,Zhang Zhang,Chen Chen

doi:10.3390/w11081543

Abstract

The focus of this paper is on studying novel approaches to estimate sediment exchange between suspended-load and bed material in an unsteady sediment-laden flow with fine-grained sand. The erosion-deposition characteristics of the channel have close relation with the variation of size compositions of both suspended-load and bed material. These aims are addressed by deducing the sediment exchange equations from the mass conservation perspective and establishing a river-sediment mathematical model based on the theory. The model is applied in the middle and lower Yellow River, China, and calibrated and verified under both deposition and erosion conditions using a generalized channel and a large quantity of measured data in the Yellow River basin. The results indicate that the grading curves of suspended-load and bed material calculated by the mathematical model are close to those of the measured data. The temporal and spatial variations in the mean sizes of suspended-load and bed material, flow rate, sediment concentration and erosion or deposition volume estimates during the entire flood process can be accurately predicted. The model performance is considered acceptable for determining the sediment exchange process and the change in channel morphology for unsteady sediment-laden flow.

Highlights

Rivers are important sources of water on the earth which are continuously changing, and sediment exchange is one of the most powerful agents in the river environment [1,2]
The variations in size compositions of suspended-load and bed material are closely related to erosion-deposition characteristics of the channel [8,9]
This paper aims to gain new insights into the principles of sediment exchange during riverbed evolution of the alluvial rivers with fine-grained sand, and proposes a novel river-sediment mathematical model to calculate the grain size, composition and exchange of both suspended-load and bed material with no need to divide the sediment into groups based on particle force analysis and mass conservation

Summary

Introduction

Rivers are important sources of water on the earth which are continuously changing, and sediment exchange is one of the most powerful agents in the river environment [1,2]. Sediment exchange transfigures the river morphology by long-term degradation and aggradation of channel beds via erosion and deposition. Sediments in a natural river, including suspended-load, bed-load, and bed material, are usually non-uniform and their size compositions strongly influence the flow capacity and consequent riverbed evolution [3,4,5]. In most alluvial rivers with fine-grained sand in plains (e.g., the middle and lower Yellow River), the proportion of bed-load is low and the sediment exchange between suspended-load and bed material dominates channel morphology change [6,7]. The erosion-deposition process is rather complex, which is affected by the interactions between turbulence structures and initiation of particles movement [10]

Objectives

Methods

Results