Seasonal variations in composite riverbank stability in the Lower Jingjiang Reach, China

Xia, Junqiang; Zong, Quanli; Deng, Shanshan; Xu, Quanxi; Lu, Jinyou

doi:10.1016/j.jhydrol.2014.10.061

Cited by 55 publications

(41 citation statements)

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“…The construction of revetment engineering for more than half a century has indicated that large‐scale bank‐erosion processes have not occurred in the study reach, especially after the construction of important submerged bank‐protection works, and these bank‐protection works restrict effectively the channel widening processes in local regions. However, remarkable channel degradation has still caused significant bank retreat at several local sites that have no revetment protection (Yu and Lu, ; Xia et al ., , c; Cao and Wang, ). Statistics of cross‐sectional profiles surveyed in 2002–2014 indicate that severe bank retreat occurred at these local sites around Jing34, Jing60, Jing98 and Jing133, as shown in Figure (b).…”

Section: Resultsmentioning

confidence: 99%

“…It is widely accepted that bank erosion is the result of a set of complex natural processes that depend on in‐channel hydrodynamic conditions and bank soil properties, which are both highly variable within a single river and between rivers, however, it is difficult to predict the process of bank erosion or the variation in bankfull width using simple relations (Thorne et al ., ; ASCE Task Committee, ; Piégay et al ., ; Bartley et al ., ; Xia et al ., , c). Repeated measurements of cross‐sectional profiles show that the left bank profile at Jing34 remained unchanged from 2002 to 2014, while the right bank retreated continuously over the same period (Figure (a)).…”

Section: Resultsmentioning

confidence: 99%

“…Several studies have been conducted to investigate the effects of the Three Gorges Project (TGP) on the flow-sediment transport and morphological changes in the Middle Yangtze Reach (MYR) downstream of the dam (Li et al, 2007;Xu and Milliman, 2009;Chen et al, 2010;Yuan et al, 2012;Dai and Liu, 2013;Xu et al, 2013;Xia et al, 2014c;Yang et al, 2014). For example, Xu and Milliman (2009) analysed variations in sediment discharge along the MYR before and after the TGP, and found that channel erosion occurred in the reach between Yichang and Datong during the initial operation period from 2003 to 2006, with an average of about 70 Mt/a of sediment being eroded in response to the release of clear water, with sharply reduced sediment concentrations.…”

Section: Introductionmentioning

confidence: 99%

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Geomorphic response of the Jingjiang Reach to the Three Gorges Project operation

Xia

Deng

Zhou

et al. 2016

Earth Surf Processes Landf

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Upstream damming often causes significant downstream geomorphic adjustments. Remarkable channel changes have occurred in the Jingjiang Reach of the Middle Yangtze River, since the onset of the Three Gorges Project (TGP). Therefore, it is important to investigate the variations in different fluvial variables, for better understanding of the channel evolution characteristics as an example of the Jingjiang Reach. Recent geomorphic adjustments in the study reach have been investigated quantitatively, including variations in sediment rating curve, fluvial erosion intensity, channel deformation volume and bankfull channel geometry. These fluvial variables adjusted in varying degrees in response to the altered flow and sediment regime caused by the TGP operation. A focus of this study has been especially on variation in the bankfull channel geometry. Calculated bankfull dimensions at section‐ and reach‐scale indicate that: (i) there were significant bank‐erosion processes in local regions without bank‐protection engineering, with empirical relations being developed to reproduce the variation in bankfull widths at four typical sections; (ii) the variation in the reach‐scale channel geometry occurred mainly in the component of bankfull depth, owing to the construction of large‐scale bank‐revetment works, with the depth increasing from 13.7 m in 2002 to 15.0 m in 2014, and with an increase in the corresponding bankfull area of about 11%; and (iii) the reach‐scale bankfull channel dimensions responded to the previous 5‐year average fluvial erosion intensity during flood seasons at Zhicheng, with higher correlations for the depth and area being obtained when calibrated by the measurements in 2002–2012. Furthermore, these relations developed for the section‐ and reach‐scale bankfull channel geometry were also verified by the observed data in 2013–2014, with encouraging results being obtained. Copyright © 2016 John Wiley & Sons, Ltd.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Geomorphic response of the Jingjiang Reach to the Three Gorges Project operation

Xia

Deng

Zhou

et al. 2016

Earth Surf Processes Landf

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“…For the cohesive upper soil in the UJR, an empirical relationship between critical shear stress (τ c ), the bulk density of the soil (γ s ), and the mean median diameter of the cohesive soil ( d 50 ) can be written as

τ_{c} = 1 / 77.5 \times ([], 3.2 ((), γ_{s} - γ_{w}) d_{50} + a / d_{50})

where γ s = 2.72 kN/m 3 for the low‐liquid‐limit clay; γ w is the bulk density of water; d 50 = 0.008 mm for the cohesive upper soil; and a is an empirical coefficient equalling 2.842 × 10 −4 N/m according to the statistics of incipient motion for clay in the Jingjiang Reach (Xia, Zong, Deng, et al, ). The critical shear stress calculated using Equation was 0.50 N/m 2 for the cohesive upper soil, which was used in the following calculations.…”

Section: Methodsmentioning

confidence: 99%

Modelling of the retreat process of composite riverbank in the Jingjiang Reach using the improved BSTEM

Zong

Xia

Deng

et al. 2017

Hydrological Processes

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Bank retreat in the Jingjiang Reach is closely related not only to the near‐bank intensity of fluvial erosion but also to the composition and mechanical properties of bank soils. Therefore, it is necessary to correctly simulate bank retreat to determine the characteristics of fluvial processes in the Jingjiang Reach. The current version of bank stability and toe erosion model (5.4) was improved to predict riverbank retreat, by inputting a dynamic water table, and calculating the approximation of the distribution of dynamic pore water pressure in the soil near the river bank face, and considering the depositional form of the failed blocks, which is assumedly based on a triangular distribution, with the slope approximately equalling the stable submerged bank slope and half of collapsed volume deposited in the bank‐toe region. The degrees of riverbank stability at Jing34 were calculated using the improved bank stability and toe erosion model. The results indicate the following trends: (a) the degrees of riverbank stability were high during the dry season and the rising stage, which led to minimal bank failure, and (b) the stability degrees were low during the flood season and the recession stage, with the events of bank collapse occurring frequently, which belonged to a stage of intensive bank erosion. Considering the effects of bank‐toe erosion, water table lag, and the depositional form of the collapsed bank soil, the bank‐retreat process was simulated at the right riverbank of Jing34. The model‐predicted results exhibit close agreement with the measured data, including the total bank‐retreat width and the collapsed bank profile. A sensitivity analysis was conducted to determine the quantitative effects of toe erosion and water table lag on the degree of bank stability. The calculated results for toe erosion indicate that the amount of toe erosion was largest during the flood season, which was a primary reason for bank failure. The influence of water table lag on the degree of stability demonstrates that water table lag was an important cause of bank failure during the recession stage.

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“…Most studies utilized the hydrological model, historical map and field survey methods to analyze the hydrological regime change in the LJR. These studies mainly focused on certain aspects, such as the flow and sediment [20][21][22][23], bank erosion and stability [24,25], river channel pattern [19,26] and hydrological effect between rivers and lakes [27,28]. The annual average sediment load at Yichang and Jianli stations in the post-dam period (2003)(2004)(2005)(2006)(2007) was reduced by 74% and 84%, respectively, compared with the pre-dam period [29].…”

Section: Introductionmentioning

confidence: 99%

Remotely Sensed Trajectory Analysis of Channel Migration in Lower Jingjiang Reach during the Period of 1983–2013

et al. 2015

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Abstract:In China, the Lower Jingjiang Reach (LJR) of the Yangtze River could be one of the most complicated areas in terms of channel migration. The river had undergone many channel changes in the reach since the 18th century. Intensive human activities in recent decades, such as the construction of upstream dams and revetments, had directly affected the channel migration characteristics. The revetment would significantly diminish migration, whereas the reduced sediment caused by dams would increase bank erosion and bank failure risks. Satellite imageries of Landsat Multi Spectral Scanner (MSS), Thematic Mapper (TM), Enhanced Thematic Mapper Plus (ETM+) and Operational Land Imager (OLI) were employed to quantify the planform migration of the reach from 1983 to 2013 and to investigate the possible effect of human activities on the LJR channel evolution. Apart from the commonly used planform morphometric parameters, the migration direction was introduced to predict the future migration trends. Results showed that the LJR was gradually changing to a straighter channel, with sinuosity reducing from 2.09 to 1.9 and river length decreasing from 125.32 km to 113.31 km in the past 30 years. Planform morphometric parameters, such as migration rate of the channel centerline and erosion and deposition areas and rates, also decreased drastically in the past 30 years. The migration rate of the channel centerline decreased from 31.05 m¨year´1 in 1983-1988 to 11.62 m¨year´1 in 2009-2013. The lateral erosion and deposition areas decreased from 21.32 and 25.73 km 2 in 1983-1988 to 4.83 and 5.83 km 2 in 2009-2013. All of these findings indicate that the LJR tended to be in a steady state from 1983 to 2013 and was totally controlled by the bank revetments. However, the undercutting was strengthened because of the restrictive effect of revetments on lateral migration in the LJR. Moreover, the channel migrated to the left bank with a visible tendency as the total migration area to the left bank was approximately two times that of the right bank during the period. Consequently, the left bank of the LJR should be the focus of more attention in future migrations, and bank revetments of the left bank should be kept reinforced and adjusted with the change of water and sediment conditions.

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Seasonal variations in composite riverbank stability in the Lower Jingjiang Reach, China

Cited by 55 publications

References 22 publications

Geomorphic response of the Jingjiang Reach to the Three Gorges Project operation

Geomorphic response of the Jingjiang Reach to the Three Gorges Project operation

Modelling of the retreat process of composite riverbank in the Jingjiang Reach using the improved BSTEM

Remotely Sensed Trajectory Analysis of Channel Migration in Lower Jingjiang Reach during the Period of 1983–2013

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