Hydrodynamic and geomorphic adjustments of channel bars in the Yichang-Chenglingji Reach of the Middle Yangtze River in response to the Three Gorges Dam operation

Lyu, Yongnan; Fagherazzi, Sergio; Tan, Guojun; Shan, Z.S.; Feng, Zhong-kai; Han, Shasha; Shu, Caiwen

doi:10.1016/j.catena.2020.104628

Cited by 34 publications

(21 citation statements)

References 47 publications

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“…Since the TGR had been in operation for more than twenty years from the interception of the Yangtze River, three criteria were employed to ensure data consistency regarding the spatial-temporal resolution and retrieval accuracy for the MCBs. Firstly, images with less cloud cover were used where possible [5,23]. Secondly, images acquired during the dry season (i.e., November to March) were used, to reduce the difference in water levels during the different stages.…”

Section: Data Collectionmentioning

confidence: 99%

“…The data preprocessing, including single-band extraction, false color synthesis and geometric correction, etc., was carried out using ENVI 5.3 software. Many previous studies proved that these images can be used to monitor the landscape dynamics with reasonable accuracy [5,23,24]. Detailed information on the collected image data is shown in Table 1.…”

Section: Data Collectionmentioning

confidence: 99%

“…This index was derived from the normalized difference water index (NDWI), which highlighted the water information in the image by normalizing the spectral difference between the green band and the mid-infrared band [38]. The MNDWI has been proved to be an effective method for retrieval of the MCBs with reasonable accuracy [5,23]. The MNDWI was calculated as:…”

Section: Retrieval Of Mcbs From Landsat Imagesmentioning

confidence: 99%

“…Furthermore, many other environmental factors affecting the development of MCBs were not considered [21,22]. In recent years, the rapid development of numerical simulation technology, remote sensing and spatial analysis in geographic information science has provided an opportunity to monitor and model the dynamics of MCBs at multi-spatial and multi-temporal scales [23,24]. Schuurman et al [15] generated datasets of water depth, flow and sediment transport of MCBs based on physical models, and further developed a conceptual network model describing the interactions of MCBs, sub-branches and river channels.…”

Section: Introductionmentioning

confidence: 99%

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Dynamics of Mid-Channel Bar during Different Impoundment Periods of the Three Gorges Reservoir Area in China

Tang

Tan

et al. 2021

Water

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The dynamics of the mid-channel bars (MCBs) in the Three Gorges Reservoir (TGR) were substantially impacted by the large water-level changes due to the impoundments of the TGR. However, it is still not clear how the morphology of the MCBs changed under the influence of water level and hydrological regime changes induced by the impoundments and operation of the TGR. In this work, the MCBs in the TGR were retrieved using Landsat remote sensing images from 1989 to 2019, and the spatio-temporal variations in the number, area, morphology and location of the MCBs during different impoundment periods were investigated. The results showed that the number and area of MCBs changed dramatically with water-level changes, and the changes were dominated by MCBs with an area less than 0.03 km2 and larger than 1 km2. The area of MCBs decreased progressively with the rising water level, and the number generally showed a decreasing trend, with the minimum number occurring at the third stage when the water level reached 139 m, resulting in the maximum average area at this period. The ratio of length to width of the MCBs generally decreased with the changes in hydrological and sediment regimes, leading to a shape adjustment from narrow–long to relatively short–round with the rising of the water level. The water impoundments of the TGR led to the migration of the dominant area from the upper section to the middle section of the TGR and resulted in a more even distribution of MCBs in the TGR. The results improve our understanding of the mechanisms of the development of MCBs in the TGR under the influence of water impoundment coupled with the annually cyclic hydrological regime and longer periods of inundation and exposure.

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Section: Data Collectionmentioning

confidence: 99%

Section: Data Collectionmentioning

confidence: 99%

Section: Retrieval Of Mcbs From Landsat Imagesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Dynamics of Mid-Channel Bar during Different Impoundment Periods of the Three Gorges Reservoir Area in China

Tang

Tan

et al. 2021

Water

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“…They are commonly present in various sized rivers around the world [2,3]. As a typical fluvial landform, MCBs are often focused on by engineering projects, such as maintaining channel stability and navigation safety [4,5]. In recent decades the ecological functions of MCBs have been gradually recognized thanks to their characteristics of isolation and edge effects [6,7].…”

Section: Introductionmentioning

confidence: 99%

Impacts of Dam Operation on Vegetation Dynamics of Mid-Channel Bars in the Mid-Lower Yangtze River, China

et al. 2021

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Vegetation dynamics on mid-channel bars (MCBs) is essential for supporting ecosystem functions and associated services in river systems, especially in dammed large rivers. Generally, there are two possible changing patterns that vegetation of MCBs downstream a dam would experience. On one hand, the vegetation area may shrink because of a decrease in the MCB area in the post-dam period, which has been observed in many rivers around the world. On the other hand, the MCB vegetation area may expand because flood disturbances would be weakened by dam operation. However, little evidence has been reported to clarify such confusion. Therefore, vegetation dynamics of MCBs in the mid-lower Yangtze River downstream the Three Gorges Dam (TGD; the world’s largest dam) is selected as a case study to address the issue. Using long-term (1987–2017) Landsat archive images, this study reveals the spatiotemporal variations of vegetation area change intensities (VACIs; indicated by dynamic trends) on MCBs in the mid-lower Yangtze River. Results show that an overall VACI in the post-dam period (2003–2017) is about three times faster than that in the pre-dam period (1987–2002). In other words, the rate of vegetation colonization accelerated after the TGD operation began in 2003. Moreover, the VACIs in the post-dam period are size dependent, where large size MCBs are likely to gain higher VACIs: Small-sized MCBs (0.33 km2/yr), medium-sized MCBs (1.23 km2/yr), large-sized MCBs (1.49 km2/yr). In addition, VACIs of individual MCBs in the post-dam period are distance dependent, where the further a MCB was from the TGD, the higher the VACI. It is also suggested that the weakened flood disturbances in the post-dam could explain the rapid vegetation growth and colonization. This work is not only beneficial for managing and protecting MCBs downstream the TGD after its operation, but is also helpful in understanding vegetation dynamics of MCBs in other dammed river systems around the world.

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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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Hydrodynamic and geomorphic adjustments of channel bars in the Yichang-Chenglingji Reach of the Middle Yangtze River in response to the Three Gorges Dam operation

Cited by 34 publications

References 47 publications

Dynamics of Mid-Channel Bar during Different Impoundment Periods of the Three Gorges Reservoir Area in China

Dynamics of Mid-Channel Bar during Different Impoundment Periods of the Three Gorges Reservoir Area in China

Impacts of Dam Operation on Vegetation Dynamics of Mid-Channel Bars in the Mid-Lower Yangtze River, China

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

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