Sandy riverbed shoal under anthropogenic activities: The sandy reach of the Yangtze River, China

Yang, Yixin; Zheng, Jinhai; Zhang, Mingjin; Zhu, Liping; Zhu, Yonghua; Wang, Jianjun; Zhao, Weiyang

doi:10.1016/j.jhydrol.2021.126861

Cited by 30 publications

(40 citation statements)

References 38 publications

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“…The operation of the Three Gorges Project resulted in long‐distance cumulative scour downstream of the dam, which was accompanied by unidirectional scour in a river section of about 166 km, with an average scour depth of 2.43 m and a maximum scour depth of 19.98 m. Compared with the average scour depth of the riverbed after dam construction for the representative rivers around the world (shown in Table 6), the average scour depth downstream of the TGD was similar, but the maximum scour depth was relatively greater. This could be due to the in‐channel gravel mining activity (Yang et al, 2021). Since TGD began operating, the reservoir has blocked a large amount of sediment from upstream, and the sediment supply downstream of the dam has been significantly reduced, which was the main cause of river scour.…”

Section: Discussionmentioning

confidence: 99%

“…Based on the sand mining survey of the Taipingkou waterway (approximately 15 km in length) in the middle reaches of the Yangtze River, the amount of illegal sand mined in the river channel during 2014–2016 accounted for 15.9% of the total erosion (Zhao et al, 2020; Yang et al, 2021). Moreover, illegal sand mining activities damage the integrity of the shoals and alter the water diversion relationship between the branched channels, such as that in the Shashi River section (Zhao et al, 2020; Yang et al, 2021). In summary, sand mining, channel dredging, and the operation of the TGD are the main reasons for the river erosion in the middle reaches of the Yangtze River, with the operation of the TGD the most dominant factor.…”

Section: Discussionmentioning

confidence: 99%

“…This model does not affect the total runoff (Chen et al, 2016); however, the volume of downstream sediment transport is greatly reduced (Xu & Milliman, 2009; Dai & Liu, 2013; Dai et al, 2014, 2016; Yang et al, 2014, 2015, 2020; Zhou et al, 2017; Guo et al, 2018; Yang et al, 2018a). Following the commissioning of the TGD, channel scouring and thalweg downcutting were observed in the Jingjiang section, and some sections exhibited lateral widening (Xia et al, 2016, 2017; Zheng et al, 2018; Yang et al, 2021). However, the implementation of shoreline protection projects reduced the length of bank collapse to pre‐impoundment levels (Huang et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

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Impact of the Three Gorges Dam on riverbed scour and siltation of the middle reaches of the Yangtze River

Yang

Zheng

Zhang

et al. 2022

Earth Surf Processes Landf

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This study investigated the influence of the Three Gorges Dam (TGD) on the evolution of nearby channels in the Yangtze River (Changjiang River) system in order to better understand the environmental impact of large‐scale reservoir operations. From 2003 to 2017, the amounts of runoff and sediment transport in the Yangtze River were reduced by 3.3–14.5% and 67.8–92.7%, respectively, relative to 1955–2002 before the TGD was operational. Topographic measurements of the middle reaches (Yichang to Hukou) of the Yangtze River were analyzed from 1975 to 2017, during which time the cumulative erosion of the flood channel was 22.78 × 108 m3, and the dry channel accounted for 90.3% of the erosion. Following commissioning of the TGD, the scouring intensity of the sandy gravel section near the dam initially increased then decreased, whereas the scouring intensity of sandy sections away from the dam continued to increase. Beaches on convex banks of curved sections were scoured, and deep channels on concave banks became silted. In braided sections, the braids tended to shrink, and the diversion ratio of the main branch during dry seasons reduced, resulting in frequent branch alternation. Compared to changes in the downstream river channels of other large reservoirs worldwide, scouring from the TGD is extensive. The findings of this study are significant for river channel regulation and waterway planning in the Yangtze River and worldwide.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Impact of the Three Gorges Dam on riverbed scour and siltation of the middle reaches of the Yangtze River

Yang

Zheng

Zhang

et al. 2022

Earth Surf Processes Landf

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“…As shown by the flow diversion ratios, the Taipingkou south branch has been dominant over the north branch, making it appropriate to select the south branch as the main branch. The flow diversion ratio of the north branch of the Sanbatan Central bar has been higher than that of the south branch in most years; therefore, the north branch was usually selected as the customary main navigable waterway during the (Zhao et al, 2020;Yang et al, 2021), the north branch of Taipingkou has been greatly erosion and a 4.5 m waterway has been opened since 2018 as a dry-season waterway, forming a two-branch navigable route.…”

Section: Relationship Between Branch Diversion and Main Waterwaymentioning

confidence: 99%

“…Meanwhile, the complex relationship between the hydrodynamic, sediment discharge, and bottomland evolution in the confluence area of Dongting Lake and the Changjiang River has been noted, a key reach for waterway management and dredging maintenance (Dong et al, 2020). Existing studies have also focused on changes in riverbed erosion and silting (Xia et al, 2016;Xia et al, 2017;Yang et al, 2017;Yang Y. et al, 2018;Yang et al, 2018b;Yang et al, 2018c), bottomland changes (Zhao et al, 2020;Yang et al, 2021), diversion relationships (Liu et al, 2017;Hu et al, 2020;Yang et al, 2021), and navigation obstruction characteristics (Yan et al, 2012;Yang et al, 2019;Li et al, 2021b) in the confluence area of Dongting Lake and Changjiang River since the operation of the Three Gorges Reservoir. The existing studies have paid little attention to the influence of the adjustment of diversion relationship of Dongting Lake on channel conditions in the intersection area of river and lake, especially the influence on the development and utilization of water depth resources in the main channel of the Changjiang River.…”

Section: Introductionmentioning

confidence: 99%

Changes of Divergence and Confluence Relationship Between Dongting Lake and the Yangtze River After the Operation of the Three Gorges Project and Its Impact on the Waterway Depth

et al. 2022

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Human activities and climate change have profoundly changed the hydrological and geomorphological evolutionary processes and trends of rivers and lakes, which, in turn, has affected the utilization of their waterway depth. This study chose the Dongting Lake–Jingjiang confluence of the Changjiang River (Yangtze Rvier), since the operation of the Three Gorges Project, the split ratio of water and the sediment distribution of the three outlets of Dongting Lake—that is, Songzikou, Taipigkou, and Ouchikou—have continued to decrease. Along with the decreasing flow of Dongting Lake, the relative increase in the runoff of the Jingjiang reach and the increase in riverbed erosion intensity have increased the relative height difference between Jingjiang and Dongting Lake, intensifying the reduction of the split ratio of water and the sediment distribution of the three outlets. The riverbed erosion of the Jingjiang reach has created a promising foundation for an increase in the waterway dimensions. However, the length of the reach not meeting the requirements of 4.5× 200 m (water depth × width) is 18.4 km, of which the length in the river-lake confluence is 12.6 km, accounting for 68.35% of the total length of obstructed navigation. Furthermore, at the reach (Zhicheng–Dabujie reach) affected by the first outlet (Songzikou), a 4.5-m flume has been formed, but its width is less than 200 m. Moreover, the “steep slope and rapid current” phenomenon is clear, and it affects the safety of ships. At the reach (Taipingkou reach) affected by the second outlet, the shrinkage of the bottomland, and the intersecting braided river channels make the low-flow routes unstable, the water depth being less than 4.5 m. At the reach (Tianxingzhou–Ouchikou reach) affected by the third outlet, the shoreline of the reach has collapsed and retreated significantly. Additionally, beach erosion and the downstream movement of cut banks have caused the downstream waterway width at the reach to be reduced to less than 200 m or formed shoals with a water depth of less than 4.5 m. Owing to the jacking effect of the lake’s outflow backwater, the flow rate of the reach (Xiongjiazhou–Chenglingji reach) affected by the confluence of Dongting Lake decreased, creating a shoal with a water depth of less than 4.5 m in the navigation waterway. The results of this study have guiding significance for understanding the changes of channel conditions and the improvement of channel scale in the intersection area of rivers and lakes.

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Impact of upstream reservoirs on geomorphic evolution in the middle and lower reaches of the Yangtze River

Yang

Liangping

Zhu

et al. 2022

Earth Surf Processes Landf

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Intensive human activities in river basins have substantial effects on fluvial hydrological and morphological processes and developmental trends. In this study, we assessed the evolutionary characteristics and developmental trends of the fluvial morphological system of the Three Gorges Dam (TGD) downstream to understand the impacts of human activities on the fluvial hydrological–morphological system of the region. The results indicated that the Three Gorges Project (TGP) and other upstream cascade reservoirs promoted sediment retention, which in turn aggravated the trend of declining sediment load and cumulative scouring over a long distance in the channels downstream of the TGD. Approximately 84% of scouring occurred in the low‐water channels, along with thalweg scouring and riverbank collapse. Notably, extended operation of the TGP and other upstream cascade reservoirs has resulted in gradual changes in the downstream riverbeds. Specifically, we found that the most intensive scouring zone shifted downstream from the near‐dam Yichang–Chenglingji reach (0–408 km) to the Chenglingji–Hankou reach. The scouring–silting distribution in swales has also changed: the scouring of deep swales and silting on floodplains prior to the TGP have been replaced by the scouring of both deep swales and floodplains. The scouring intensity of riverbeds in the Yichang–Hukou reach (954 km) was slightly higher than that forecasted prior to the TGP; the scouring intensities increased significantly during 2013–2021, which could be attributed to the TGP and other upstream cascade reservoirs; river sand mining and waterway dredging are secondary factors. We conclude that, owing to the effects of sediment retention by cascade reservoirs in the upper reaches of the Yangtze River (or Changjiang River), the cumulative scouring intensities of riverbeds in the middle and lower reaches of the Yangtze River will continue to increase in future decades.

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Sandy riverbed shoal under anthropogenic activities: The sandy reach of the Yangtze River, China

Cited by 30 publications

References 38 publications

Impact of the Three Gorges Dam on riverbed scour and siltation of the middle reaches of the Yangtze River

Impact of the Three Gorges Dam on riverbed scour and siltation of the middle reaches of the Yangtze River

Changes of Divergence and Confluence Relationship Between Dongting Lake and the Yangtze River After the Operation of the Three Gorges Project and Its Impact on the Waterway Depth

Impact of upstream reservoirs on geomorphic evolution in the middle and lower reaches of the Yangtze River

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