Flow Characteristics and Bed Morphology in a Compound Channel between Two Single Channels

Weiming Wu,Xingnian Liu,Ruihua Nie,Xudong Ma,Lu Wang

doi:10.3390/w12123544

Abstract

In mountainous areas, a river can widen from a single channel to a compound channel under the influence of geological conditions or human impacts, bringing about challenges in terms of flood control and channel regulation. This paper reports the results of tests conducted in a 26 m long flume with a uniform sediment bed (grain size = 0.5 mm), investigating the flow characteristics and bed morphology in a compound channel between two single channels. The stage‒discharge relationship in the compound channel and the longitudinal and cross-sectional bed profile in the compound channel between two single channels are presented and analyzed. The experimental results indicate that the flow characteristics and bed morphology in a compound channel between two single channels are significantly different from those in a normal compound channel. Based on the experimental data and observations, the mechanisms of flow and sediment transport in the compound channel between two single channels are illuminated.

Highlights

A river can widen from a single channel to a compound channel with floodplains due to the influence of geological conditions or human factors (e.g., the Tongluoxia reach, the Qutangxia reach of the Yangtze River, the Pengshan reach of Min River (Figure 1), etc.)
This study presented experiments investigating the flow characteristics and bed morphology in a compound channel between two single channels
Based on the experimental results, the following conclusions were reached: The experimental results indicate that the water level at the middle of the compound channel generally increases with increasing flow discharge

Summary

Introduction

A river can widen from a single channel to a compound channel with floodplains due to the influence of geological conditions or human factors (e.g., the Tongluoxia reach, the Qutangxia reach of the Yangtze River, the Pengshan reach of Min River (Figure 1), etc.). Many studies have investigated the flow characteristics and sediment transport in compound channels (i.e., rivers have a main channel with floodplains) [1,2,3,4,5,6,7,8]. The conventional divided cross section method divides a compound channel into a main channel and a floodplain by making a plumb line along the boundary. This method does not consider the shear stress between the main channel and the floodplain, causing a large calculation error [15,16]. Ackers [19,20,21] modified the divided cross section method based on the concept of river channel coherence (COH), introducing the discharge correction factor (DISADF)

Methods

Results

Conclusion