Riverbed erosion of the final 565 kilometers of the Yangtze River (Changjiang) following construction of the Three Gorges Dam

Zheng, Shuwei; Xu, Yanqing; Cheng, Heqin; Wang, Bo; Xu, Weihua; Wu, Shuaihu

doi:10.1038/s41598-018-30441-6

Cited by 62 publications

(41 citation statements)

References 49 publications

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“…Hence, an understanding of the morphological impacts on tidal dynamics becomes increasingly important. The TGD's operation lead to a dramatic reduction in sediment supply in the www.nature.com/scientificreports www.nature.com/scientificreports/ YRE 56 , increasing erosion 61 and causing channel deepening, which reduces bottom friction 79,81,82 . It reduces tidal attenuation along the channel 41 , resulting in increased tidal amplitudes at most stations after the TGD's operation (Fig.…”

Section: Changes In the Tidal Duration Asymmetry Between The Pre-and mentioning

confidence: 99%

“…To mitigate floods and droughts in the middle and lower regions of the Yangtze River, the TGD reduces the peak discharge in the wet season whereas increases discharge during the dry season 48,49,59 . The riverine sediments are mostly trapped in reservoirs, causing severe channel erosion in the subaqueous delta 4,60,61 . These seasonal discharge regulation and morphological changes significantly affect the tidal dynamics in the YRE.…”

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confidence: 99%

“…Cai et al 63 investigated the effects of the TGD on spatiotemporal variations in tide-river dynamics, with the largest change occurring in autumn. In addition, the YRE has undergone significant morphological changes under the influences of human activities such as dam constructions and land use patterns 45,56,61,64,65 , which also affect the tidal duration asymmetry in the system. Hence, a better understanding of the relationship between tidal duration asymmetry and river discharge and morphology with respect to the TGD is still missing.…”

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Impact of river discharge seasonality change on tidal duration asymmetry in the Yangtze River Estuary

Zhang

Hoitink

2020

Sci Rep

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the Yangtze River estuary (YRe) is one of the world's largest river-tidal systems with rapidly changing hydrology and morphology following the construction of multiple dams. The effects of dam construction may extend to the region close to the coast, where channel stability depends on the asymmetry of the tide. Here, we focus on the possible effects of changing discharge regimes on tidal asymmetry in the YRE. Specifically, we focus on the difference in duration between ebb and flood, quantified as tidal duration asymmetry, because it has strong implications for residual sediment transport and can be derived from available water level data. To cope with nonstationary tides under the influence of a time-varying river discharge, a nonstationary harmonic analysis tool (NS_TIDE) is applied to explore the spatiotemporal variations in tidal duration asymmetry, under the influence of different combinations of tidal constituents. Tidal duration asymmetry initially increases, then slightly decreases, in an upstream direction. It experiences significant seasonal variations in response to rapidly varying discharge: tides are more asymmetric upstream of Zhenjiang in the dry season and more asymmetric downstream in the wet season. The combined effects of discharge regulation and morphological changes cause seasonal alterations in tidal duration asymmetry. In the wet season, reduced river discharge caused by water storage and climate change enhance the asymmetry upstream (+11.74% at Wuhu, +7.19 at Nanjing) while the asymmetry is weakened downstream (−2.90% at Zhenjiang, −7.19 at Jiangyin) following the TGD's operation. Downstream channel erosion caused by post-TGD lower sediment loads has become the dominant factor weakening tidal asymmetry in most parts of the YRe in the dry season. Understanding these evolutions of tidal duration asymmetry under the hydrological and morphological effects has important implications for the management of estuarine ecosystem and navigation. Dams are built for various purposes, such as irrigation, flood control and power generation 1. The various impacts of dams have been subject to study and debated for decades. The changes in river and sediment discharges due to dam constructions have long been recognized as far-reaching 2-4. Dams play an important role in eliminating peak river discharge and stabilizing low river discharge 5. Beyond discharge regulation, dams also lead to a drop in sediment loads, thereby impacting estuarine morphology 4,6-9 , which is crucially dependent on tidal asymmetry 10,11. Here, we focus on tidal duration asymmetry, which quantifies the periodic difference between the durations of falling and rising tidal water level 12,13. Tidal duration asymmetry characterizes flood and ebb dominance 14-16 , and can directly be derived from long-term water level data. Tidal asymmetry can be produced when tides propagate into shallow-water areas, where tidal distortion results in rising high-frequency harmonic constituents 14,17. The physical mechanisms responsible for tidal duration ...

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Section: Changes In the Tidal Duration Asymmetry Between The Pre-and mentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Impact of river discharge seasonality change on tidal duration asymmetry in the Yangtze River Estuary

Zhang

Hoitink

2020

Sci Rep

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“…Numerous case studies, even in recent past, dealt with the issue of river response to dam regulation (Gao et al ., ; Adib et al ., ; Zhang et al ., ; Zheng et al ., ). However, a consensus is building on the need of predictive mechanisms that can forecast possible channel response to dam building and operation.…”

Section: Introductionmentioning

confidence: 97%

Predicting dam‐related downstream geomorphic response with widely available stream gauge data: A case study of the Godavari River Basin, India

Sanyal

Kanae

2020

Singap J Trop Geogr

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Dam-related downstream adjustments of riverbeds are normally investigated by analysing the trend in sediment supply and high flow events during the pre-and post-dam periods. The required data for existing predictive models is not measured at river gauges, which limits the application of these tools. We derived the frequency of sediment-transporting streamflow events (T*) and upstream sediment supply (S*) in the pre-and post-dam periods with widely available gauged records and predicted changes in the downstream riverbed by adapting an existing model. Ten gauging stations in the Godavari River Basin, India, located downstream of dams, were chosen as study sites. Annually surveyed cross-sections at each site validated the accuracy of the predicted dam-related downstream changes. Then, a regression equation (R 2 = 0.75) was established between T*/S* (independent variable) and changes in the downstream bed elevation (dependent variable) for the Godavari Basin. We recommended that similar local empirical equations be formulated for larger river basins. Models of large-scale rainfall-runoff and sediment transport processes that can account for the influence of dams, such as the Soil & Water Assessment Tool, can be paired with the proposed regression equation to estimate dam-related downstream erosion and deposition with globally available data.

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“…development) (Xu et al, 2006). This is especially the case for the downstream reach of the three gorges dam (TGD) on the Yangtze River as it passes through one of the country's most densely populated and most industrialized region Zheng et al, 2018). The survey in very early 1980s found hundreds of MCBs with a total area over 1000 km 2 in the downstream of the TGD (downstream of Yichang) (Sun, 1984).…”

Section: Introductionmentioning

confidence: 99%

Three-decadal dynamics of mid-channel bars in downstream of the Three Gorges Dam, China

Wen

Yang

Ding

et al. 2019

Preprint

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Abstract. The downstream of the world’s largest Three Gorges Dam (TGD) along Yangtze River (1560 km) hosts numerous mid-channel bars (MCBs). The morphodynamics of these MCBs are crucial to the river’s hydrological processing, local ecological functioning, and socioeconomic development. However, a systematic understanding of such dynamics and their linkages to the TGD across the entire downstream reach remain largely unknown. Using Landsat archive images and a thematic extracting scheme, the work presents comprehensive monitoring of MCB dynamics in terms of number, area, and shape, in the downstream of the TGD during 1985–2018. Total 140 MCBs were extracted and grouped into four types to represent small size (< 2 km2), middle size (2 km2–7 km2), large size (7 km2–33 km2) and extra-large size (> 33 km2) MCBs, respectively. Most of the MCBs in terms of number (70 %) and total area (91 %) were concentrated in the lower reach (Hankou to Estuary). The number of small size MCBs decreased after TGD closure and most of such decreasing events happened in the lower reach. Although all four types of MCBs showed overall increasing trends in area, small MCBs had smaller rate and received more influence by the TGD operation than the large MCBs. Small size MCBs tended to become relatively shorter and wider whereas the others became slimmer after TGD operation. Impacts from the TGD operation could decrease along with the increasing distance from TGD to Hankou (for shape dynamics) or to Jiujiang (for area dynamics). The quantified longitudinal and temporal dynamics of MCBs across the whole downstream of the TGD provides a crucial monitoring basis for continuous investigations of changing mechanisms in the morphology of the Yangtze River system.

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Riverbed erosion of the final 565 kilometers of the Yangtze River (Changjiang) following construction of the Three Gorges Dam

Cited by 62 publications

References 49 publications

Impact of river discharge seasonality change on tidal duration asymmetry in the Yangtze River Estuary

Impact of river discharge seasonality change on tidal duration asymmetry in the Yangtze River Estuary

Predicting dam‐related downstream geomorphic response with widely available stream gauge data: A case study of the Godavari River Basin, India

Three-decadal dynamics of mid-channel bars in downstream of the Three Gorges Dam, China

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