Abstract
The sediment-laden floodplain flood is affected by beach vegetation and the shape of curved compound channels. The laws of water and sediment exchange and deposition distribution in beach troughs are very complex and play a significant role in the formation and development of secondary suspended rivers, the adjustment of beach horizontal gradients, and even the evolution of flood control situations. This study used a combination of experimental simulations and theoretical research to carry out a generalized model test of floodplain flood evolution, analyzing the transverse distribution characteristics of sediment-laden flow and sediment factors in a curved compound channel under the conditions of beach vegetation, proposing a theoretical model of transverse distribution of velocity and sediment concentration that is based on the momentum equation considering the inertial force of the lateral secondary flow and river curvature. The results showed the following: (1) The model test results for floodplain flood in the compound channel with curved vegetation showed that the main stream was not only concentrated in the main channel but also appeared near the foot of the left and right bank levees and formed flood discharge along the embankment, as the beach siltation was mainly concentrated in the beach lip; (2) The arrangement of full vegetation on the beach had a uniform effect on the velocity distribution of the beach, which can reduce the phenomenon of excessive velocity at the foot of the beach and increase the velocity effect in the main channel; and (3) Through five numerical examples, the lateral velocity distribution model of a curved compound channel with beach vegetation was tested and, in general, the analysis model was consistent with the experimental results. The research results will provide a theoretical basis for river management and have great significance for enriching the basic theory of water and sediment movement and promoting the integration of hydraulics, river dynamics, and ecology.
Highlights
A natural river is usually composed of a main channel through the main stream and a beach that carries additional flow
With the implementation of various test conditions, the velocity distribution continued to develop and change, which provided a reference for studying the erosion and deposition evolution of beach vegetation on curved compound channels
The results showed that the arrangement of full vegetation on the beach had a uniform effect on the velocity distribution, which can reduce the phenomenon of excessive velocity on the side wall of the beach and increase the velocity in the main channel (Figure 3)
Summary
A natural river is usually composed of a main channel through the main stream and a beach that carries additional flow. Under the action of gravity and centrifugal force, the curved water flow will produce unique motion characteristics that are mainly manifested as the vertical and horizontal gradient of the water’s surface, the transverse circulation, the redistribution of the vertical average velocity, etc. It is a complex three-dimensional spiral turbulent flow that makes the characteristics of flow and sediment movement in curved channels different from that in straight channels. The characteristics of flow in a curved channel determine the basic laws of sediment movement and riverbed evolution, which have an important impact on riverbed evolution, river regulation, bank protection, etc. [2,3]
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