In 1994, workers broke ground on China's Three Gorges Dam. By its completion in 2012, the dam had transformed the ecology of the Yangzi River, displaced over a million people, and forever altered a ...landscape immortalized in centuries of literature and art. The controversial history of the dam is well known; what this book uncovers are its unexpected connections to the cultural traditions it seems to sever. By reconsidering the dam in relation to the aesthetic history of the Three Gorges region over more than two millennia,Fixing Landscapeoffers radically new ways of thinking about cultural and spatial production in contemporary China. Corey Byrnes argues that this monumental feat of engineering can only be understood by confronting its status as a techno-poetic act, a form of landscaping indebted to both the technical knowledge of engineers and to the poetic legacies of the Gorges as cultural site. Synthesizing methods drawn from premodern, modern, and contemporary Chinese studies, as well as from critical geography, art history, and the environmental humanities, Byrnes offers innovative readings of eighth-century poetry, paintings from the twelfth through twenty-first centuries, contemporary film, nineteenth-century British travelogues, and Chinese and Western maps, among other sources.Fixing Landscapeshows that premodern poetry and visual art have something urgent to tell us about a contemporary experiment in spatial production. Poems and paintings may not build dams, but Byrnes argues that the Three Gorges Dam would not exist as we know it without them.
The impoundment of the 660-km long reservoir behind the huge Three Gorges Dam, the world's largest hydropower station, increased regional seismicity and reactivated severe geohazards. Before the ...reservoir filling was initiated in 2003, the region had approximately two earthquakes per year with magnitudes between 3.0 and 4.9; after the full impoundment in 2008, approximately 14 earthquakes per year occurred with magnitudes between 3.0 and 5.4. In addition, hundreds of landslides were reactivated and are now in a state of intermittent creep. Many landslides exhibit step-like annual pattern of displacement in response to quasi-regular variations in seasonal rainfall and reservoir level. Additional problems include rock avalanches, impulse waves and debris flows. The seriousness of these events motivated numerous studies that resulted in 1) Better insight into the behavior and evolution mechanism of geohazards in the Three Gorges Reservoir Area (TGRA); 2) Implementation of monitoring and early-warning systems of geohazards; and 3) Design and construction of preventive countermeasures including lattice anchors, stabilizing piles, rock bolts, drainage canals and tunnels, and huge revetments. This paper reviews the hydro-geologic setting of TGRA geohazards, examines their occurrence and evolution in the past few decades, offers insight learned from extensive research on TGRA geohazards, and suggests topics for future research to address the remaining challenges.
The construction of the huge Three Gorges reservoir affected a large region, and the resultant geological and environmental impacts have caused global concern. The remarkable, 30-m annual fluctuation ...in the reservoir water level poses a significant threat to slope stability in this area. Four hundred sixty-two landslides were identified in the Zigui basin using historical records, satellite images, field investigations and unmanned aerial vehicle (UAV) observations, enabling the construction of a complete landslide database and distribution map. Three failure modes of landslides in the Zigui basin are used to illustrate the major factors that govern reservoir-induced landslides. The results show that (1) > 99% of identified landslides occur on slopes angle <47°, while >80% occur at elevations below 600 m; (2) Jurassic Niejiashan Formation is highly prone to landslides; (3) Low reservoir levels of 145 m to 155 m greatly reduce slope stability. Based on the information entropy method that use the conditional probability of different influencing factors and principal component analysis as inputs, the relative contributions of various influencing factors are quantified and a landslide susceptibility map was drawn. This susceptibility map helps define the countermeasures that will best reduce fatalities and property losses for areas having different landslide conditions and susceptibilities.
•Database of 462 reservoir-induced landslides in Zigui basin, TGR was created.•Identifying failure modes and quantifying contributions of influential factors.•Conditional probability and information entropy model yields landslide susceptibility.•Susceptibility map, failure modes, and strategies suppressing the slope instability.
Changes in riverine suspended and riverbed sediments have environmental, ecological and social implications. Here, we provide a holistic review of water and sediment transport and examine the human ...impacts on the flux, concentration and size of sediment in the Yangtze River in recent decades. We find that most of the fluvial sediment has been trapped in reservoirs, except for the finest portion. Furthermore, soil-conservation since the 1990s has reduced sediment yield. From 1956-1968 (pre-dam period) to 2013–2015 (post-dams and soil-conservation), the sediment discharge from the sub-basins decreased by 91%; in the main river, the sediment flux decreased by 99% at Xiangjiaba (upper reach), 97% at Yichang (transition between upper and middle reaches), 83% at Hankou (middle reach), and 77% at Datong (tidal limit). Because the water discharge was minimally impacted, the suspended sediment concentration decreased to the same extent as the sediment flux. Active erosion of the riverbed and coarsening of surficial sediments were observed in the middle and lower reaches. Fining of suspended sediments was identified along the river, which was counteracted by downstream erosion. Along the 700-km-long Three Gorges Reservoir, which retained 80% of the sediment from upstream, the riverbed gravel or rock was buried by mud because of sedimentation after impoundment. Along with these temporal variations, the striking spatial patterns of riverine suspended and riverbed sediments that were previously exhibited in this large basin were destroyed or reversed. Therefore, we conclude that the human impacts on sediment in the Yangtze River are strong and systematic.
•Sediment flux decreased by 77%–99% in the Yangtze mainstem after dams.•Active riverbed erosion and surficial sediments coarsening were observed.•Human impact on Yangtze River sediment is basin-wide, very strong and systematic.
The measurement of topography and of topographic change is essential for the study of many geomorphic processes. In recent years, structure from motion (SfM) techniques applied to photographs taken ...by camera-equipped unmanned aerial vehicles (UAVs) has become a powerful new tool for the generation of high resolution topography. The variety of available UAV systems continues to increase rapidly, but it is not clear whether increased UAV sophistication translates into improved quality of the calculated topography. To evaluate the lower end of the UAV spectrum, a simple low cost UAV was deployed to calculate high resolution topography in the Daan River gorge in western Taiwan, a site with a complicated 3D morphology and a wide range of surface types, making it a challenging site for topographic measurement. Terrestrial lidar surveys were conducted in parallel with UAV surveys in both June and November 2014, enabling an assessment of the reliability of the UAV survey to detect geomorphic changes in the range of 30cm to several meters. A further UAV survey was conducted in June 2015 in order to quantify changes resulting from the 2015 spring monsoon. To evaluate the accuracy of the UAV derived topography, it was compared to terrestrial lidar data collected during the same survey period using the cloud-to-cloud comparison algorithm M3C2. The UAV-generated point clouds match the lidar point clouds well, with RMS errors of 30–40cm; however, the accuracy of the SfM point clouds depends strongly on the characteristics of the surface being considered, with vegetation, water, and small scale texture causing inaccuracies. The lidar and SfM data yield similar maps of change from June to November 2014, with the same areas of geomorphic change detected by both methods. The SfM-generated change map for November 2014 to June 2015 indicates that the 2015 spring monsoon caused erosion throughout the gorge and highlights the importance of event-driven erosion in the Daan River. The results suggest that even very basic UAVs can yield data suitable for measuring geomorphic change on the scale of a channel reach.
•Comparison of repeat lidar and low cost UAV-derived point clouds of a bedrock gorge•Repeat UAV surveys can reliably detect changes greater than ~30cm on the reach scale.•Erosion in the Daan River is controlled by storm size rather than total precipitation.
The Secchi disk depth (ZSD) plays a critical role in describing water clarity. Several studies have shown linkages between Three Gorges Dam (TGD) and the downstream lacustrine ecosystem in the middle ...and lower Yangtze River basin. However, the potential influence on the ZSD fluctuation in the entire anthropogenic reservoirs of Three Gorges (ER) and Dongting Lake (DTL) has not been reported, possibly due to technical obstacles in obtaining statistically significant spatial and temporal results. We addressed this challenge by using remote sensing technology: the Landsat 8 Operational Land Imager (OLI). We proposed a new, robust remote-sensing algorithm to estimate ZSD from OLI imagery using red and green band-ratio, leading to MAPE of 21.68% and RMSE of 0.076m for ZSD ranging from 0.1m to 1.05m. After satisfactory image-based validation, the algorithm was implemented on OLI data to derive ZSD patterns over ER and DTL from 2013 to 2017. Several crucial findings can be drawn: 1) Spatial-temporal patterns of ZSD exhibited notable fluctuations over both ER and DTL, and they also demonstrated a significant correlation with each other because of the opposite temporal cycle of ZSD fluctuations between ER and DTL; 2) Temporally, monthly fluctuations of ZSD between ER and DTL had opposite temporal cycles, which was mainly attributed to the surface runoff and sediment discharge driven by the outbound runoff variations of TGD. Spatially, the heterogeneity of the ZSD pattern in ER might have resulted from the different geographical regions being divided by large anthropologic hydrological facilities, such as TGD; 3) The relationship between ZSD and total suspended matter (TSM) showed a significant negative correlation, as did the relationship between ZSD and Kd(490). These findings demonstrate that TSM often plays a principal role in light attenuation of extremely turbid inland waters; 4) An inversed phenomenon of water clarity was observed at the intersection of DTL and the Yangtze River around Chenglingji site (YRAC), which was due to the opposite temporal cycle of ZSD fluctuations between DTL and ER after the impoundment of TGD; and 5) Owing to the analysis of noise-equivalent ZSD, OLI data can be used to derive ZSD, since the imagery uncertainty is 0.07m by means of our band-ratio algorithm, which demonstrates similar results to MODIS. The proposed ZSD-derived algorithm in this study could be suitable for other turbid lakes or reservoirs to formulate related strategies of water quality management in the middle and lower Yangtze River basin, and the unveiled findings here improve our understanding of ZSD spatiotemporal fluctuations in large river-connected lakes, such as Poyang Lake.
Display omitted Relationships between (a) monthly surface runoff and monthly ZSD values of sub-regions in the entire large anthropogenic reservoirs of Three Gorges (ER), (b) monthly sediment discharge and monthly ZSD values of sub-regions in ER, (c) monthly surface runoff and monthly outbound runoff at Three Gorges Dam (TGD) and Gezhouba Dam (GZBD), and (d) monthly sediment discharge and monthly outbound runoff at TGD and GZBD.
•A Landsat 8 OLI-based empirical band-ratio algorithm for ZSD estimation was proposed.•The marked spatiotemporal patterns of ZSD were mapped in TGR and DTL.•Inversion of ZSD values were observed between TGR and DTL.•The potential driving forces that affect ZSD patterns were revealed.•The noise-equivalent ZSD of OLI and other current sensors were discussed.
Mountainous regions are inherently susceptible to geohazards, such as landslides and debris flows, with the threat of natural disasters compounded by human activities (mainly settlements). Lessons ...learned from past events that involved the interactions between human activities and geohazards are helpful for future site selections of human settlements in mountainous regions. To this end, the events associated with county seat relocations in Badong, a typical county in the Three Gorges Reservoir region, China, are studied from an engineering geologist's perspective. Over its history, the county seat was relocated multiple times, with the first relocation traced back to the Song dynasty (960–1279 CE) and the last two relocations linked to the Three Gorges Dam project. By studying geohazards and their interactions with human activities in these county-seat relocations, and through the reconstruction of these events, we secure insights into decision-making for these events. As part of the reconstruction of these relocation events, we analyze a giant pre-historic landslide, whose discovery ultimately prompted the third relocation. Using the case history of this landslide, we also discuss and emphasize the importance of proactive monitoring of geohazards for disaster resilience enhancement, recognizing that our knowledge of nature is vastly incomplete.
•The events associated with county seat relocations in Badong, a county in the Three Gorges Reservoir region, China, are studied.•Geohazards and their interactions with human settlements played a significant role in each relocation of the county seat.•The importance of proactive monitoring of geohazards for disaster resilience enhancement in mountainous regions is discussed.
Heavy metal (HM) contamination in sediments of Three Gorges Reservoir (TGR) is a particularly important issue for the safety of water quality due to the potential threats of metal toxicity to local ...and downstream human health. Surface sediments from riparian and submerged areas in the entire TGR mainstream were collected in 2014 to investigate the spatial distribution of HMs (Cd, Cu, Pb, and Zn), identify their possible sources, and assess their potential risk by multiple indices and metal fraction. Results showed that the concentrations of HMs in the sediments increased after the TGR operation, but were lower than those in other Chinese rivers of developed areas. The acid-soluble Cd accounted for more than 50% of total Cd in the sediments, whereas that of other HMs was very low. The Cd concentrations in the riparian sediments increased towards the dam; however, other metals in the riparian sediments and all HMs in the submerged sediments did not show any regular variation trend spatially. The stocks of HMs were significantly higher in the submerged sediments than in the riparian sediments. The high accumulation of HMs in the riparian sediments emerged between Fuling and Fengjie, and those in the submerged sediments existed in the near dam areas. Grain size and Fe/Mn oxides controlled the mobility and transfer of HMs in the sediments. Human activity in the catchment including industrial and agricultural production, shipping industry, mining, etc., increased inputs of HMs in the sediments, and altered their spatial distribution patterns. The sediments were moderately to highly contaminated by Cd, and slightly contaminated by other HMs. The results indicate the current priority of Cd contamination in the TGR, and will conduce to ecological protection in the TGR region.
Display omitted
•Distribution of Cd, Cu, Pb and Zn in sediments of the entire TGR mainstream was investigated.•HMs stocks concentrated in middle riparian zones and near dam submerged areas.•Sediment grain size and chemical conditions determined HMs mobility.•TGR operation and local human activity controlled HMs distribution in sediments.•TGR mainstream sediments were moderately to highly contaminated by Cd.
Human activity in the catchment of Three Gorges Reservoir increased heavy metal accumulation in the riparian and submerged sediments.
Among the machine learning models used for landslide susceptibility indexes calculation, the support vector machine (SVM) is commonly used; however, SVM is time-consuming. In addition, the ...non-landslide grid cells are selected randomly and/or subjectively, which may result in unreasonable training and validating data for the machine learning models. This study proposes the self-organizing-map (SOM) network-based extreme learning machine (ELM) model to calculate the landslide susceptibility indexes. Wanzhou district in Three Gorges Reservoir Area is selected as the study area. Nine environmental factors are chosen as input variables and 639 investigated landslides are used as recorded landslides. First, an initial landslide susceptibility map is produced using the SOM network, and the reasonable non-landslide grid cells are subsequently selected from the very low susceptible area. Next, the final landslide susceptibility map is produced using the ELM model based on the recorded landslides and reasonable non-landslide grid cells. The single ELM model which selects the non-landslide grid cells randomly, and the SOM network-based SVM model are used for comparisons. It is concluded that the SOM-ELM model possesses higher success and prediction rates than the single ELM and SOM-SVM models, and the ELM has a considerably higher prediction efficiency than the SVM.
•Reasonable non-landslides are selected from the very low susceptible area produced by self-organizing-map (SOM) network.•SOM-extreme learning machine (ELM) is successfully used to map landslide susceptibility in Wanzhou district.•SOM-ELM possesses higher accuracy than single ELM and SOM-support vector machine (SVM) models.•ELM has higher prediction efficiency than SVM for susceptibility indexes calculation.
The evolutionary history of the Yangtze River plays a key role for understanding the Cenozoic landscape evolution of East Asia. The Three Gorges currently separate the Sichuan Basin from the Jianghan ...Basin to the east, and their formation is considered to establish an initial connection between the Upper and Middle reaches of the modern Yangtze River. However, despite their importance in the Yangtze River evolution, the age of the initial incision of the Three Gorges remains an ongoing debate. In this study, we use apatite-fission track and (UTh)/He data to model the thermal history of the crust during the gorge formation. Based on the modeled time–temperature paths of samples on vertical profiles and the 3D thermos-kinematic modeling of the gorge region, we suggest that the gorges were initially carved during the Late Oligocene–Early Miocene. This event connected the drainages to the west and east of the gorge regions, leading to the formation of the modern east-flowing Yangtze River. This is also consistent with the sediment provenance of the Yangtze Gravels in the Lower Yangtze reported in previous studies. The gorge formation could be a response to the base level drop in the Jianghan and Subei Basins, which led to an upstream propagation of high erosion rates in the Three Gorges areas.
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•Incision of the Three Gorges is a key step in the evolution of the Yangtze River.•AFT and AHe dating used to investigate the timing of gorge incision.•Time-temperature history suggests two rapid cooling events.•3D modeling predicts an incision onset age at ~18–27 Ma.•Subsidence of East China drives the drainage reorganization via headward erosion.
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