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Effects of Riparian Plant Roots on Bank Erosion Process of Tarim River Based on BSTEM Model

Author(s): Ruize Tang; Quanli Zong; Bo Feng; Jiwang Yuan

Linked Author(s): Quanli Zong

Keywords: BSTEM; Bank erosion; Riverbank stability; Riparian roots; Tarim River

Abstract: The Tarim River is the longest inland river in China, which is located in the extremely arid Tarim Basin in northwest China. The riverbank is mainly composed of fine sand and coarse sand and other non-cohesive soil. The river bank is low in strength and vulnerable to water erosion. The roots of riparian vegetation play an important role in maintaining the stability of riparian slope and protecting embankment, which has an important influence on the scouring process of river bank. The Tarim River is rich in vegetation, mainly including Populus euphratica, Tamarix ramosissima, and Alhagi sparsifolia. The root-soil composition composed of vegetation root and riparian soil greatly improves the bank strength, and plays a role in reducing river erosion and enhancing bank stability. In order to determine the quantitative impact of riparian vegetation on the scouring process of riverbank in the Tarim River, this paper is based on the previous field sampling and laboratory test results, including six typical riparian vegetation sampling results: Alhagi sparsifolia (AS), Tamarix ramosissima (TR), Phragmites australis (PA), Glycyrrhiza uralensis (GU), Populus euphratica (PE) and Nitraria tangutorum (NT). The BSTEM model was used to simulate the scouring process of the river bank in 2016 and 2017, and the quantitative influence of riparian vegetation roots on the scouring process was quantitatively analyzed. The results show that: (i) Plant roots mainly provide additional cohesion to sediment by forming sand-root composites with sediment, thereby enhancing the shear strength of riparian soil. The cohesion of soil increases with the increase of root-soil area ratio (RAR), but the additional cohesion provided by different plant roots is different. The results are as follows: GU > PA > TR > NT > AS > PE; (ii) Vegetation roots can effectively reduce the amount of bank erosion. By simulating the bank erosion process in two hydrological years, the amount of bank erosion reduction under different vegetation roots was obtained, which was in descending order as follows: NT (reduced by 49.36 % ), GU (reduced by 32 % ), TR (reduced by 28.06 % ), AS (reduced by 24.61 % ), PE (reduced by 21.61 % ), PA (reduced by 5.07 % ); (iii) Vegetation root system reduced the possibility of riverbank scouring width and collapse. When vegetation cover, the width of riverbank collapse retreat: TR decreased by 1.01 m, PE decreased by 3.02 m, PA decreased by 0.66 m, AS decreased by 1.95 m. At the same time, the safety factor Fs of riverbank under vegetation cover was higher than that of riverbank without vegetation cover at each scouring stage.

DOI:

Year: 2022

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