No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Clustering stream profiles to understand the geomorphological features and evolution of the Yangtze River by using DEMs
Abstract
Stream morphology is an important indicator for revealing the geomorphological features and evolution of the Yangtze River. Existing studies on the morphology of the Yangtze River focus on planar features. However, the vertical features are also important. Vertical features mainly control the flow ability and erosion intensity. Furthermore, traditional studies often focus on a few stream profiles in the Yangtze River. However, stream profiles are linked together by runoff nodes, thus affecting the geomorphological evolution of the Yangtze River naturally. In this study, a clustering method of stream profiles in the Yangtze River is proposed by plotting all profiles together. Then, a stream evolution index is used to investigate the geomorphological features of the stream profile clusters to reveal the evolution of the Yangtze River. Based on the stream profile clusters, the erosion base of the Yangtze River generally changes from steep to gentle from the upper reaches to the lower reaches, and the evolution degree of the stream changes from low to high. The asymmetric distribution of knickpoints in the Hanshui River Basin supports the view that the boundary of the eastward growth of the Tibetan Plateau has reached the vicinity of the Daba Mountains.
The topological system of lakes and streams is the basis for deriving a multitude of patterns and processes in hydrology, geomorphology and ecology. Flow direction is key to constructing a lake‐stream topological system. However, lakes and streams are important hydrological objects that should be considered since they are linked during the process of material and energy transportation. Therefore, a flow direction algorithm that can clearly express the topological relationship of lakes and streams, was proposed here. Lakes and streams were taken as the hydrological objects in stream networks and coupled into a flow direction algorithm. A topological system was established based on the proposed algorithms. Six areas on the Tibetan Plateau were chosen as sample areas with the MERIT digital elevation model (DEM) as the DEM data source. Streams derived from flow direction data in the HydroSHEDS data set (HYDROSTREAMS) and MERIT hydro data set (MERITSTREAMS), as well as streams derived from flow direction results of the D‐infinity algorithm and priority‐flood algorithm were compared with streams derived from the proposed algorithm. The topological relationship between streams and lakes was clearly expressed by the proposed algorithm. In lake areas, the proposed algorithm showed better performance, and no parallel streams were found. In nonlake areas, the stream networks derived from these algorithms were stable. The proposed algorithm offers an opportunity to treat lakes and streams differently during simulation, thus adding to the authenticity of the simulation.
Digital terrain analysis (DTA) is one of the most important contents in the research of geographical information science (GIS). However, on the basis of the digital elevation model (DEM), many problems exist in the current research of DTA in geomorphological studies. For instance, the current DTA research appears to be focused more on morphology, phenomenon, and modern surface rather than mechanism, process, and underlying terrain. The current DTA research needs to be urgently transformed from the study of landform morphology to one focusing on landform process and mechanism. On this basis, this study summarizes the current research status of geomorphology-oriented DTA and systematically reviews and analyzes the research about the knowledge of geomorphological ontology, terrain modeling, terrain derivative calculation, and terrain analytical methods. With the help of DEM data, DTA research has the advantage of carrying out geomorphological studies from the perspective of surface morphology. However, the study of DTA has inherent defects in terms of data expression and analytic patterns. Thus, breakthroughs in basic theories and key technologies are necessary. Moreover, scholars need to realize that DTA research must be transformed from phenomenon to mechanism, from morphology to process, and from terrain to landform. At present, the research development of earth science has reached the critical stage in which the DTA research should focus more on geomorphological ontology. Consequently, this study proposes several prospects of geomorphology-oriented DTA from the aspects of value-added DEM data model, terrain derivatives and their spatial relations, and macro-terrain analysis. The study of DTA based on DEM is at a critical period along with the issue on whether the current GIS technology can truly support the development of geography. The research idea of geomorphology-oriented DTA is expected to be an important exploration and practice in the field of GIS.
The objective of this study was to identify potential runoff storage zones based on the various physical characteristics of the Vishwamitri watershed using a GIS-based conceptual framework that combines through analytic hierarchy process using multi criteria decision-making method. The conceptual framework will help to identify potential runoff storage zones for water storage sites based on the various physical characteristics (rainfall, slope, land use/land cover, height above the nearest drainage, stream order, curve number, topographic wetness index) of the watershed. It was found out that 17% of the area is optimally suitable, 33.2% of the area is moderately suitable, 33.1% of the area is marginally suitable and 18.7% of the area is not suitable for water storage zones/ structures. Results will help concerned authorities in the proficient arrangement and execution of water-related plans and schemes, improve water shortage, reduce dependability on ground water and ensure sustainable water availability for local and agricultural purposes in the study area. ARTICLE HISTORY
Assessing and attributing vegetation dynamics can provide essential information for environmental resources management, particularly for those regions with fragile ecosystems. The Yangtze River Basin (YRB), a region of pivotal importance to the ecological balance and security of China, has experienced dramatic changes in environment and landscape driven by climate change and human activities, especially afforestation projects in recent years. Yet how the driving factors contribute quantitatively to vegetation dynamics is not well established. Here we investigate spatiotemporal variability of vegetation coverage in terms of the Enhanced Vegetation Index (EVI) over 2001–2015, and analyze the actual influences of various climatic factors on EVI inter-annual variations. Further analysis quantifies the contributions of climate change and anthropogenic factors to EVI inter-annual variations. The results show that over the 15-year period, the average EVI demonstrated fluctuations but denoted a generally upward trend, with an increasing rate of 0.0027/a. According to the Hurst exponent analysis, areas with consistent improvement were primarily concentrated in Hunan Province and eastern Sichuan Province, where the main vegetation types are broadleaf forest and mixed forest. The average contributions of temperature, precipitation and solar radiation to EVI inter-annual variations in the YRB was 0.0041/a, 0.00012/a, and −0.0034/a, respectively. Temperature was the controlling climate factor, with the greatest contribution to EVI inter-annual variations, while solar radiation made strong negative contributions. The average contributions of climate change and anthropogenic factors to EVI inter-annual variations were 0.0008/a and 0.0019/a, accounting for 70.37% and 29.63% of the total EVI changes respectively. Human activities, especially ecological afforestation projects, were the main driving factors improving vegetation coverage in the YRB, and the spatial distribution of forest gains was consistent with the positive contribution of human activities to the EVI trend. However, urbanization has occupied the growth space of vegetation and was a negative human-induced factor affecting vegetation growth.
It has long been suggested that climate shapes land surface topography through interactions between rainfall, runoff and erosion in drainage basins1–4. The longitudinal profile of a river (elevation versus distance downstream) is a key morphological attribute that reflects the history of drainage basin evolution, so its form should be diagnostic of the regional expression of climate and its interaction with the land surface5–9. However, both detecting climatic signatures in longitudinal profiles and deciphering the climatic mechanisms of their development have been challenging, owing to the lack of relevant global data and to the variable effects of tectonics, lithology, land surface properties and human activities10,11. Here we present a global dataset of 333,502 river longitudinal profiles, and use it to explore differences in overall profile shape (concavity) across climate zones. We show that river profiles are systematically straighter with increasing aridity. Through simple numerical modelling, we demonstrate that these global patterns in longitudinal profile shape can be explained by hydrological controls that reflect rainfall–runoff regimes in different climate zones. The most important of these is the downstream rate of change in streamflow, independent of the area of the drainage basin. Our results illustrate that river topography expresses a signature of aridity, suggesting that climate is a first-order control on the evolution of the drainage basin.
Natural disaster vulnerability can intuitively reflect the susceptibility of an area to environmental changes. Better understanding the spatial distribution of natural disaster vulnerability is a critical process for taking effective adaptation and management. Although significant achievements have been made in disaster vulnerability, few studies are known about natural disaster vulnerability at the national scale, especially from the typical natural disaster events in China. In this study, with normalizing selected indicators and calculating vulnerability index, we analyzed the spatial distribution of natural disasters vulnerability during 2010–2017 using the geospatial techniques. The results showed that natural disaster vulnerability has certain spatial differences, but different natural disaster can occur in the same area during the study period. Drought disaster can occur in all regions of China, especially in Inner Mongolia. Flood disaster is mainly concentrated in the middle and lower reaches of the Yangtze River and the Yellow River Basin. The wind and storm disaster is chiefly in the northern regions in China. The freezing disaster is widely distributed in China. Furthermore, the regions with low vulnerability were primarily distributed in the eastern coastal region, indicating that the rapid development of economy and technology can resist or mitigate natural disaster to a certain extent. This study offers a solution to study natural disasters and provides scientific basis for disaster prevention and mitigation actions.
Depressions in grid digital elevation models (DEMs) need to be dealt with before the topographic attributes (such as specific catchment area) and terrain features (such as drainage networks) related to flow directions can be derived from DEMs in a hydrologically-correct manner. Many depression-processing algorithms, which adopt different strategies and take different information under consideration for determining correct flow directions in depressions, have been proposed. However, currently, there is still no one algorithm which can satisfactorily deal with depressions in grid DEMs under various application contexts. In this paper, we review existing depression-processing algorithms based on the adopted strategies (i.e. the DEM-revising strategy and the DEM-unchanging strategy). Algorithms with the DEM-revising strategy especially are discussed in detail according to their designs relating to the revision of DEM elevations, i.e. the smoothing filter, depression filling, depression breaching (or carving), using other qualified data, and applying different algorithms to depressions with different characteristics. Existing ways of improving the computation efficiency of depression-processing algorithms are also presented, i.e. serial algorithm optimization and parallel algorithms. Lastly, we discuss a possible design for an optimal depression-processing algorithm which may be developed in the future.
Gravity and GPS hybrid measurements were conducted at 385 stations throughout the Qinling Orogen, China, to update Bouguer gravity anomalies and free-air gravity anomalies of the area. The crustal density structure, lithosphere flexure mechanism, and isostatic state of the Qinglin Orogen were studied in detail via these in situ observations. Bouguer gravity anomalies in the study area are mainly negative, ranging from −410 mGal in the Tibetan Plateau to −100 mGal in the eastern Qinglin Orogen. The estimated crustal thickness ranges from 56 to 35 km and thins eastward along the Qinling Orogen. The optimal effective elastic thickness (Te) of the study area is 14 km, and the loading comes from the Earth's surface, the interface between the upper and lower crust, and the Moho. Vertical tectonic stress borne by the lithosphere varies observably in the study area. Downward stress reaches a peak of −14 MPa in the Liupanshan Mountains, whereas the highest value of upward stress (8 MPa) is attained in the middle Qinling Orogen. Considering distributions of crustal density structures and vertical tectonic stress of the lithosphere, in addition to the distinct loading ratios of the eastern and western Qinling Orogen, a piecewise combination model was developed to interpret the uplift of the Qinling Orogen. This model shows that the eastern part of the Orogen is thickened by the upward migration of mantle materials under the thrusting of the South and North China Blocks, whereas uplift of the western part results from lower crustal flow derived from the Tibetan Plateau.
Determining high-resolution three-dimensional (3-D) crustal structures of the Qinling Orogenic Belt (QOB) can reveal significant evidences to enhance our understanding of its tectonic evolution. By jointly inverting group and phase velocity dispersion curves, we obtain a high-resolution 3-D shear wave velocity model for the QOB. According to the obviously layered features, which include an E-W trending high-velocity structure in the upper crust (0–10 km), a transitional zone in the middle crust (10–30 km), and an approximately N-S trending low-velocity zone in the middle-lower crust (20–40 km), we elucidate the crustal structure as a flyover model to explain how the crust beneath the QOB was deformed under the perpendicular force systems from the NE-SW and E-W directions during the Meso-Cenozoic. First, the apparent NE-SW trending low-velocity zone in the middle-lower crust indicates that the low-viscosity crustal materials beneath the northeastern Tibetan Plateau did not flow eastward into the eastern Qinling terrane during the Cenozoic. Second, the extension in the northern Qinling Mountains and Weihe Basin was not largely affected by the lateral crustal growth of the NE Tibetan Plateau, which might be the result of deep mantle upwelling and/or residual effects from the subduction of the western Pacific plate. Third, during the Mesozoic, the high-velocity structures beneath the Hannan-Micang and Shennongjia-Huangling domes served as anchors resisting the northward subduction, rotation, and continuous collision of the Yangtze Block. The eastward extruding Hannan-Micang dome served as an indenter that eventually shaped the present-day asymmetric style of the Dabashan Orocline during the Cenozoic.
Geomorphometry, the science of digital terrain analysis (DTA), is an important focus of research in both geomorphology and geographical information science (GIS). Given that 70% of China is mountainous, geomorphological research is popular among Chinese scholars , and the development of GIS over the last 30 years has led to significant advances in geomorphometric research. In this paper, we review Chinese progress in geomorphometry based on the published literature. There are three major areas of progress: digital terrain modelling methods, DTA methods, and applications of digital terrain models (DTMs). First, traditional vector-and raster-based terrain modelling methods, including the assessment of uncertainty, have received widespread attention. New terrain modelling methods such as unified raster and vector, high-fidelity, and real-time dynamic geographical scene modelling have also attracted research attention and are now a major focus of digital terrain modelling research. Second, in addition to the popular DTA methods based on topographical derivatives, geomorphological features, and hydrological factors extracted from DTMs, DTA methods have been extended to include analyses of the structure of underlying strata, ocean surface features and even socioeconomic spatial structures. Third, DTMs have been applied to fields including global climate change, analysis of various typical regions, lunar surface and other related fields. Clearly, Chinese scholars have made significant progress in geomorphometry. Chinese scholars have had the greatest international impact in areas including high-fidelity digital terrain modelling and DTM-based regional geomorphological analysis, particularly in the Loess Plateau and the Tibetan Plateau regions.
Combining 121 new fission-track and (U-Th)/He ages with published thermochronologic data, we investigate the Late Cretaceous–Cenozoic exhumation/cooling history of the eastern Tibetan Plateau, Qinling, Daba Shan, and Sichuan Basin of east-central China. The Qinling orogen shows terminal southwestward foreland growth in the northern Daba Shan thrust belt at 100–90 Ma and in the southern Daba Shan fold belt at 85–70 Ma. The eastern margin of Tibet Plateau experienced major exhumation phases at 70–40 Ma (exhumation rate 0.05–0.08 mm/yr), 25–15 Ma (≤1 mm/yr in the Pengguan Massif; ~0.2 mm/yr in the imbricated western Sichuan Basin), and since ~11–10 Ma along the Longmen Shan (~0.80 mm/yr) and the interior of the eastern Tibet Plateau (Dadu-River gorge, Min Shan; ~0.50 mm/yr). The Sichuan Basin records two basin-wide denudation phases, likely a result of the reorganization of the upper Yangtze-River drainage system. The first phase commenced at ~45 Ma and probably ended before the Miocene; >1 km of rocks were eroded from the central and eastern Sichuan Basin. The second phase commenced at ~12 Ma and denudated the central Sichuan Basin, Longmen Shan, and southern Daba Shan; more than 2 km of rocks were eroded after the lower Yangtze River had cut through the Three Gorges and captured the Sichuan-Basin drainage. In contrast to the East Qinling, which was weakly effected by Late Cenozoic exhumation, the West Qinling and Daba Shan have experienced rapid exhumation/cooling since ~15–13 Ma, a result of growth of the Tibetan Plateau beyond the Sichuan Basin.
The inhomogeneous and non-flat paleotopography in a depositional landform area profoundly controls the process of modern gully evolution and shapes the structure of a gully network. However, this controlling effect of paleotopography on modern gully evolution is mostly ignored because of the difficulties in paleotopography reconstruction. In this study, loess area in China is selected as case area for its typical depositional landform area and inhomogeneous and non-flat paleotopography during the Quaternary. The paleotopography underlying loess is considered while evaluating its controlling effects on the gully evolutionary process. On the basis of the geophysical prospecting, detailed geological information, and high-resolution digital elevation model, we reconstruct the pre-Quaternary paleotopographic surface in the case area. Comparative analysis is conducted to reveal the modern gully evolution in relation to the paleotopography. Results show that the concave area of the paleotopography acts as the basement of the high-order modern gully evolution in the hilly-gully area, although this concave area can be covered and buried by the loess depositional process during the Quaternary. A significant controlling effect of paleotopography on high-order modern gully evolution can be observed in a depositional landform with a hilly-gully underlying topography, whereas a relatively weak controlling effect exists in a flat underlying topographical area because of the strong horizontal shift effect of gully formation process. Several low-order modern gullies also exist and limit the controlling effect of paleotopography. These results reveal a controlled high-order modern gully evolutionary process and a rather dynamic low-order modern gully evolutionary process in the hilly-gully area. These results also help us understand the variations in different modern gully evolution in relation to paleotopography and the different management schemes for soil conservation and ecological restoration during the gully evolutionary process.
The underlying pre-existing paleotopography directly influences the loess deposition process and shapes the morphology of current loess landforms. An understanding of the controlling effects of the underlying paleotopography on loess deposition is critical to revealing the mechanism of loess-landform formation. However, these controlling effects exhibit spatial variation as well as uncertainty, depending on a study's data sources, methodologies and particular research scope. In this study, the geological history of a study area in the Loess Plateau of China that is subject to severe soil erosion is investigated using detailed geological information and digital elevation models (DEMs), and an underlying paleotopographic model of the area is constructed. Based on the models of modern terrain and paleotopography, we introduce a watershed hierarchy method to investigate the spatial variation of the loess-landform inheritance relationship and reveal the loess deposition process over different scales of drainage. The landform inheritance relationships were characterized using a terrain-relief change index (TRCI) and a bedrock terrain controllability index (BTCI). The results show that the TRCI appears to have an inverse relationship with increasing research scope, indicating that, compared with the paleotopography of the region, modern terrain has lower topographic relief over the entire area, while it has higher topographic relief in the smaller, local areas. The BTCI strengthens with increasing drainage area, which demonstrates a strong controlling effect over the entire study area, but a weak effect in the smaller, local areas because of the effect of paleotopography on modern terrain. The results provide for an understanding of the spatial variation of loess deposition in relation to paleotopography and contribute to the development of a process-based loess-landform evolution model.
The natural flow properties of the Yangtze River have been changed completely following the construction of the Three Gorges Dam. The dam's operation has affected the resources and environment in the middle and lower reaches of the Yangtze River, changing the hydrological conditions and ecological environment of the Dongting Lake. During three different dispatching periods of the reservoir, we took triplicate samples of the river and lake water. All the samples were analysed for δ(2)H and δ(18)O to determine the relationship between the lake and the Yangtze River (and other rivers), and to evaluate objectively the influence of the dam's operation on the lake. During the period of water-supply dispatch, the Four Rivers and Miluo River are the main recharge sources of the lake. During the flood-storage dispatching period, the Dongting Lake is recharged largely by the Three Outlets and the Four Rivers, whereas during the period of water-storage dispatch, most of the lake's water originates from the Miluo, Xiang, Zi, and Yuan rivers. Although the Yangtze River only contributes significantly to the lake's recharge through the Three Outlets during the flood-storage dispatching period, the lake discharges large amounts of water into the Yangtze River during all three periods. Through the operation of the reservoir, it should be ensured that the water level of the Dongting Lake is not too low during the dry season, nor too high during the wet season, thus preventing the lake region from future flood and drought disasters.
Abstract[Correction added after online publication 3 August 2010 ‐ ‘prelate’ has been changed to ‘pre‐late’ throughout the text]. Using apatite fission track and (U‐Th‐Sm)/He thermochronology, we report the low‐temperature thermal history of the Mesozoic Micang Shan Foreland Basin system, central China. This system, comprising the Hannan Dome hinterland, the northern Sichuan Foreland Basin and the intermediate frontal thrust belt (FB), shares a common boundary with three major tectonic terrains – Mesozoic Qinling‐Dabie Orogen, Mesozoic Sichuan Foreland Basin and Cenozoic elevated Tibetan Plateau. Results show: (1) a relatively rapid pre‐late Cretaceous cooling episode in the Hannan Dome; (2) a mid‐Cenozoic cooling phase (ca. 50°C at ca. 30 ± 5 Ma) within the northern Sichuan Basin; and (3) possible late Cenozoic cooling (ca. 25°C at ca. 16 ± 4 Ma) within the Hannan Dome‐FB, a phase which has also been reported previously from adjacent regions. The pre‐late Cretaceous cooling episode in the Hannan Dome is attributed to coeval tectonism in nearby regions. Mid‐Cenozoic cooling in the northern Sichuan Basin can possibly be attributed to either one of or a combination of shortening of the basin, onset of the Asian monsoon and drainage adjustment of the Yangtze River system, all of which are related to growth of the Tibetan Plateau. Possible late Cenozoic cooling in the hinterland and nearby regions is also probably related to the northeastward growth of the Tibetan Plateau. However, previous studies suggest a northeastward propagation for onset of cooling from the eastern Tibetan Plateau to western Qinling in response to northeastward lower crust flow from the central Tibetan Plateau. The timing of apparent late Cenozoic cooling in the Hannan Dome hinterland, at an intermediate locality, is not consistent with this trend, and supports a previous model suggesting northeastern growth of the Tibetan Plateau through reactivation of WE trending strike‐slip faults.
The evolution of loess-covered landforms is largely controlled by the pre-Quaternary underlying bedrock terrain, which is one of the most important factors in understanding the formation mechanism of the landforms. This study used multiple data sources to detect 1729 outcropping points of underlying terrain, in order to construct a digital elevation model (DEM) of the paleotopography of an area of the Loess Plateau subject to severe soil erosion. Four terrain characteristics, including terrain texture, slope gradient, the hypsometric curve, and slope aspect, were used to quantify topographic differences and reveal the loess-deposition process during the Quaternary. A loess thickness map was then created to show the spatial distribution of loess deposits in the test area. Finally, the geomorphological inheritance characteristics of the loess-covered landforms were evaluated in different landform divisions. The results showed the significant inheritance of modern topography from the underlying topography with a similar general relief trends. The average thickness of loess deposits was computed to be 104.6 m, with the thickest part located in the Xifeng loess tableland area. In addition, the slope aspects of the North and Northwest seem to have favored Quaternary loess deposition, which supported the hypothesis of an eolian origin for loess in China. The modern surface has lower topographic relief compared to the underlying terrain due to loess deposition.
River incision and drainage reorganization have an important impact on the site selection of many major projects including city, road and others, and are the key issues of Quaternary environmental changes. Studies of river incision and river-network adjustment have traditionally been based on extensive field evidence, such as sediment age and beheaded river system. The Buyuan River basin is a large sub-basin of the upper Lancang-Mekong, with high mountains and extremely active erosion. The latter affects the preservation of the Quaternary period sediments leading to difficulties in understanding the main evolution characteristics of the basin. This study investigates differences in the equilibrium state of the longitudinal profile, infers incision rates, and evaluates drainage divide migration timelines using the stream-power incision model, the latest morphological dating, and Chi-plots (χ-z) based on digital elevation models (DEMs) on the GIS software platform. The final results show that two significant erosion base-level decreases occurred in the Late Pleistocene at least. The incision rate of the mainstream might have been 0–2.99 mm/yr since 100 ka BP and 0–3.28 mm/yr since 46 ka BP. The Chi-values across the divides suggest that space limited (or constrained) river reorganization and that there is no severe reorganization in the basin; the imbalance of traceable erosion only exists in local areas. The main driving force for the geomorphologic evolution of the Buyuan River basin is likely climate fluctuations rather than strong tectonic uplift since the Late Pleistocene.
Bibliometrics was used to statistically analyze key zones within the Yangtze River Basin (YRB) funded by the National Natural Science Foundation of China (NSFC) and national ministries over the past 20 years. This study determined that funds that derived from national ministries have mainly focused on issues related to environmental pollution, ecological security, technological water regulations, and river basin ecosystems, which offer a better understanding of the national requirements and the scientific knowledge of the YRB in combination with data from the NSFC. Under a background of bolstering the construction of green ecological corridors in the economic belt of the YRB, this study proposes future conceptual watershed research initiatives in this region as a study objective by reinforcing the implementation of the Chinese Ecosystem Research Network (CERN) and by emphasizing the use of new technologies, new methods, and new concepts for the prospective design of frontier research under the perspective of geoscience and earth system science. This study promotes large-scale scientific field and research objectives based on big science and big data.
Continental collision between India and Eurasia plates and associated compression result in the formation of the Tibetan Plateau with a mean elevation of >5000 m. However, how the plateau was formed is still under debate. In this study, by analyzing multiple topographic metrics in the Dadu River drainage basin, eastern Tibetan Plateau, together with previous studies, we attempt to unravel the landscape development there. Our results reveal significant differences in the obtained topographic metrics within the Dadu River drainage basin: higher values of hypsometric integral (HI), normalized stream length gradient (SLK), topographic relief, slope and channel steepness in the middle section of the drainage basin between 29.2° N and 31° N, and lower values in the upper (north of 31° N) and lower sections (south of 29.2° N). Meanwhile, these topographic metrics show a good match with the millennial-scale erosion rates but the long-term exhumation rates contrast between the upper Dadu and the lower Dadu despite similar topographic metric values. We infer that the topographic patterns in the Dadu River drainage basin are related to river capture between the Dadu and Anning Rivers which resulted in the adjustment of the landscape in the middle section of the Dadu River drainage basin with additional incision occurred but not enough to be recorded by low temperature thermochronometric ages.
Variations in the water level of tide-influenced deltas are strongly related to the evolution of tides as the tidal waves propagate upriver. However, the impacts of tidal species on these water level variations are not well understood, particularly in delta channel networks. Therefore, a one-dimensional hydrodynamics model of the Pearl River Delta channel networks was established to investigate the impacts of different tidal species on the distribution of the water level. Spatial distributions of the amplitude of four main tidal species (the diurnal (D1), semidiurnal (D2), quarterdiurnal (D4), and fortnightly (D1∕14) tidal species) were extracted using the continuous wavelet transform method. The results reveal that the diurnal and semidiurnal tidal species dominate the fluctuation in the water level near the river outlets, but are significantly attenuated in the upstream direction. The quarterdiurnal tidal species strengthens in shallow waters and then decays farther upriver. However, the fortnightly tidal species grows upriver. There is a strong resemblance between the distribution patterns of the water level and that of the amplitude of the fortnightly tidal species in the Pearl River Delta channel networks. Moreover, in the upstream channels, dominant fortnightly tides lead to the occurrence of lowest low water levels on neap tides rather than the expected spring tides. The results of this study have significant implications for the investigation of hydrodynamic processes and the management of navigation safety in delta channel networks.
The Daba Shan Orocline is located in the northeastern Sichuan Basin, and has undergone foreland propagation and distinct surface uplift owing to the eastward expansion of the Tibetan Plateau since the late Cenozoic. In order to describe and quantify the earth surface processes respond to deep geological mechanisms, and to detect the kind of tectonic deformation in the Daba Shan area during the late Cenozoic, various geomorphic indices were analyzed for study area. The obtained results are: (1) The northeast of the Hanzhong Basin, the Hannan-Micang Massifs, along the Chengkou-Fangxian fault, and the Shennongjia Massif exhibit intense tectonic activity. (2) The spatial patterns of the channel steepness indices indicate that the western segment of the northern Daba Shan (Fenghuang Shan and Paotaizi region) have higher uplift rates than the eastern. (3) The longitudinal profile analysis revealed that the landscape evolution of the Shennongjia Massif is in a transient state, with an uplift amplitude of 1700–1900 m since the end of the Paleogene (25 Ma), and an average uplift rate of 0.072 ± 0.004 mm/a. The paleochannel reconstruction indicate an incision of ~900–1000 m since the late Neogene (3.0–3.4 Ma), with the average uplift rate being 0.3 ± 0.03 mm/a. (4) Three tectonic deformation zones can be distinguished in the Daba Shan (from west to east), the shortening deformation, strike-slip deformation, and vertical uplift zones. These observations suggest that the eastward growth of the Tibetan Plateau has affected the Daba Shan area and shaped the modern landscape.
The formation of barge networks on rivers and associated inland port systems is subject to a complex set of influencing factors and mechanisms. This paper aims to present a comprehensive comparative empirical analysis focusing on the container shipping (barge) network in the Yangtze and the Rhine. This analysis is supported by extensive datasets on both river basins, incorporates the latest development on both rivers and is grounded on concepts and methods coming from transport geography and economic geography. We find that a large diversity might exist in how inland port systems and related gateway seaports are dealing with cargo flows and supply chains. In view of explaining this diversity, we make a distinction between geographical/nautical aspects, macro-economic factors and institutional/governance factors. In particular, we discuss the role of institutional and governance factors in barge network development by using the concepts of selection, retention and variation.
p>Estuary morphologies are dynamic systems, and their stabilities are dependent on various forcing conditions, including tides, waves, and fluvial inputs. However, during the past half century, massive anthropogenic interventions have occurred in many estuaries around the world, resulting in substantial changes in morphologies. Here, we examine such changes in the Yangtze estuary to study decadal morphological stability under anthropogenic disturbances using an entropy-based approach. Using a numerical model, the influence of bathymetric changes and sea-level rise on the variations in energy within the South Branch was examined. An analysis of the spatiotemporal bathymetric variations suggested that the South Branch can be subdivided into three segments of the lower, middle and upper reaches. The changes in these three segments relative to a theoretical equilibrium state were used to investigate and attribute the causes of change. It was found that (1) reclamation works in the South Branch during the last half century, primarily the Xuliujing reclamations (before 1980s) in the upper reach and the Changxing Island expansion (Qingcaosha Reservoir project, 2002–2007) in the lower reach, moved the system away from equilibrium by 2.5–3% in total, although the natural evolution between 1987 and 1997 restored some of the lost efficiency; (2) before large-scale reclamations, river flooding disturbed the system away from equilibrium by 3–6% in 1958, but this was mitigated by 1–2% due to the reclamation works that constrained the channel and deepened the subtidal area; (3) an entropy-based analysis suggested that the Xuliujing reclamation introduced a river constraint that influenced the reach ~20 km downstream, and by enclosing the Qingcaosha Reservoir, a tidal constraint was introduced that influenced the reach ~30 km upstream; and (4) morphological adjustment within the South Branch (a form of self-organization) has enabled the system to adjust to the imposed changes toward a new dynamic equilibrium, consistent with the prevailing constraints and forcing conditions. The results of this study demonstrate a method to determine estuary stability in the context of human interventions, and this method may be relevant to other estuaries subject to large-scale changes.</p
The expression of gully landforms can be regarded as an indicator of the evolutionary process of gullies. Most existing studies on the expression of gully landforms focus on plane characteristics. However, the vertical characteristics of a gully should be given considerable attention because gullies have mainly eroded the surface in the vertical direction. Current studies on vertical characteristics of gullies mainly focused on a single gully or rarely a few gullies, thereby failing to express the entire gully landform in a certain area. In this study, gully profile combination (GPC) was proposed to investigate the morphology and reveal the evolution of gully landforms. It was defined as the combination of vertical projection of all gully profiles in the entire drainage basin. Then, a gully evolution index and its statistic values were used to reveal the evolution of gully landforms based on GPC. The proposed method was applied and validated in three typical loess gully landform areas (i.e., loess tableland, ridge, and hill) in the Loess Plateau of China. Results show that GPC can effectively express gully landforms. The specific geomorphological feature (monoclinic loess tableland) can also be identified using GPC. The gully evolution index results also demonstrate different magnitudes of gully evolutionary stages in a certain area, which reflect the diversity of gullies. The average and median values of the gully evolution index increase in the three typical loess gully landforms. From loess tableland, loess ridge, and loess hill, the average values are 0.653, 0.703, and 0.763, and the median values are 0.661, 0.719, and 0.783, respectively. This method is also found to be stable with gully extraction thresholds for distinguishing different loess gully landforms. Accordingly, the evolution magnitudes of loess gully are obtained.
A comparative comparative study on the detrital mineral composition of stream sediments of the Yangtze River (Changjiang) and Yellow River (Huanghe) shows that, light minerals of the Yangtze River basin were mainly quartz, feldspar, and detritus, the compositional characteristics of light minerals differed among tributaries, the main stream had a generally higher maturity index than tributaries; heavy mineral content tended to decrease progressively from the upper stream to lower stream of the Yangtze River, the primary assemblage was magnetite-hornblende-augite-garnet-epidote, and diagnostic minerals of different river basins were capable of indicating the nature and distribution of the source rock. Detrital mineral assemblages in sediments of tributaries and the main stream of the Yellow River were basically similar, Primary heavy mineral assemblage was opaque mineral-garnet-epidote-carbonate mineral and alteration mineral. Variations in the contents of garnet, opaque mineral, and hornblende mainly reflected the degree of sedimentary differentiation in suspended sediment and the hydrodynamic intensity of a drainage system. The heavy mineral differentiation index F revealed sedimentary differentiation of diagnostic detrital mineral composition due to changes in regional hydrodynamic intensity and can serve as an indicator for studying the dynamic sedimentary environment of a single-provenance river and the degree of sedimentary differentiation of its detrital minerals. Changes in detrital mineral content of the Yellow River was not completely controlled by provenance but reflected gravity sorting of the detrital mineral due to variations in the ephemeral river hydrodynamic intensity and sedimentary environment, however the index changing of Yangtze River were mainly influenced by the complex sediment sources. Therefore caution must be exercised in using the detrital mineral composition of marginal sea to determine the contribution of the Yangtze River and Yellow River.© 2019 China Geology Editorial Office.
At the initial stage of dam operation in an alluvial river, significant vertical bed incision and transverse bank erosion processes always occur in the river reach downstream of the dam, with the latter being usually an integrated product of several interacting processes. A coupled two-dimensional (2D) model for the processes of bed evolution and bank erosion has been proposed in this study, which integrates a 2D morphodynamic module with a bank-erosion module and a groundwater flow module. In addition to the action of fluvial erosion, the effect of groundwater flow on bank erosion was considered, with the changes in pore water pressure and matrix suction being calculated. The proposed model was calibrated and validated through simulating channel evolution processes in a 30.54 km sub-reach of the Upper Jingjiang Reach of the Middle Yangtze River, with the effects of infiltration recharge on bank erosion and incoming flow on the central bar evolution being investigated. The results show that: (i) the proposed model had a good performance in reproducing flow and sediment factors, in terms of water depth, depth-averaged velocity and suspended sediment concentration, daily averaged discharge and river stage, and flow and sediment diversion ratios in local anabranching subreaches; (ii) the proposed model correctly calculated the bank erosion processes in the study reach, with the calculated bank retreat width being close to the measured value, however, it was not enough to fully reproduce the evolution of central bars, indicating that a specialized and improved module may be necessary for central bar evolution and its interaction with bank erosion; (iii) the groundwater level change lagged behind the river stage variation, and it showed a more obvious phase lag and a higher value at the same river stage (corresponding to a higher pore water pressure), when encountering with a more rapidly changing river stage; and (iv) the rate of infiltration recharge caused by rainfall process, would generally increase the groundwater level and thus the bank erosion degree in the study reach. In addition, the shifting of incoming main flow might take an obvious impact on the calculation of nearby central bar evolution.
Focusing on the Yangtze River economic zone, the previous geological researches are systematically summarized, resources and environment conditions and major geological problems which are needing to be concerned in land planning and construction are studied. The results show that the resource conditions of cultivated land, shale gas, geotherm, lithium and so on are superior in the Yangtze River economic zone, and the resources and environment conditions are conducive to develop the modern agriculture, clean energy industry and strategic emerging industries. 3×1013 m2 farmlands without heavy metal pollution are concentrated; there are three national level shale gas exploration and development bases with explored reserves of 5.441×1011 m3; geothermal availability is 2.4×109 t of standard coal each year, equivalent to 19% of the amount of coal in 2014; Asia’s largest energy lithium metal ore deposit is found. In some parts of Yangtze River economic zone, there are some major geological problems such as active faults, karst collapse, ground subsidence, landslide-collapse-debris flow, affecting the river-crossing channels, high-speed railway, urban agglomeration and green ecological corridor planning and construction. Those problems should be concerned, and the relevant suggestions and countermeasures are put forward. Meanwhile, the ideas to further support the development of the Yangtze River economic zone are put forward.
Blowouts are wind‐eroded landforms that are widely distributed in the north‐eastern part in Qinghai‐Tibet Plateau (QTP), China. These blowouts are thought to form in response climate change and/or human activity but little is known about their morphodynamics. Using field surveys, remote sensing and GIS spatial analysis, the distribution and morphology of blowouts are analysed and their initiation considered. Results show the QTP mega‐blowouts are some of the largest in the world. The orientations of the trough shaped blowouts are parallel with the prevailing wind, but the saucer and bowl‐shaped blowouts are influenced by bi‐directional transport. Whilst regional patterns of blowout shape and size were observed to reflect the extent of aeolian sediments and wind regimes, the relationship between the different morphological parameters showed consistency. During initial stages of development, the length‐width ratios of blowouts increase rapidly with area but after they reach a mega size this relationship stabilizes as blowouts widen. Initial luminescence dating shows that blowouts appear to have initiated ~100 to 500 years ago, coinciding with the Little Ice Age (LIA) climate event when northwest winds are known to have intensified. Further work is required to confirm this initiation period and establish the significance of mega blowouts for landscape degradation and human activities.
Dam operation profoundly modifies downstream flow-sediment regimes, resulting in a variety of geomorphologic responses, without uniform laws. The Jingjiang reach of the middle Yangtze River has undergone significant adjustment mode alterations, with intensive channel erosion and major adjustment area changing from the bankfull channel to the medium flow channel at the time boundary of the Three Gorges Dam (TGD) impoundment. While these changes have received some attention, little work has been undertaken to reveal the reason. In this study, based on 172 cross sections measured in the post-flood period from 2003 to 2015, different river patterns, longitude and reach-averaged channel dimensions were assessed to reflect the channel adjustment characteristics of the Jingjiang reach. An index has been proposed to measure the cumulative water transport capacity of each discharge interval and to assess the relationship with reach-scale medium flow channel dimensions. The results indicate that the channel adjustment changes are directly driven by the alterations of flow duration and sediment transport capacity. With the deficiency of floods, medium flow channels respond quite well to small and medium discharges of under approximately 16,500 m³/s. A discharge of 16,500 m³/s which can be regarded as a critical threshold, corresponds to the average top levels of braided and meandering channel bars, which are of morphological significance in constraining the passing flow in the medium flow channel. Small and medium discharges under the critical threshold associate with relatively larger reductions in sediment loads and hold increased geomorphic impacts (QmJP), eventually resulting in adjustment mode alterations. The results present herein for the Jingjiang reach of the Yangtze River can provide a better understanding of dam operation and the corresponding impacts on downstream channel morphology.
Scale is the basic attribute for expressing and describing spatial entity and phenomena. It offers theoretical significance in the study of gully structure information, variable characteristics of watershed morphology, and development evolution at different scales. This research selected five different areas in China’s Loess Plateau as the experimental region and used DEM data at different scales as the experimental data. First, the change rule of the characteristic parameters of the data at different scales was analyzed. The watershed structure information did not change along with a change in the data scale. This condition was proven by selecting indices of gully bifurcation ratio and fractal dimension as characteristic parameters of watershed structure information. Then, the change rule of the characteristic parameters of gully structure with different analysis scales was analyzed by setting the scale sequence of analysis at the extraction gully. The gully structure of the watershed changed with variations in the analysis scale, and the change rule was obvious when the gully level changed. Finally, the change rule of the characteristic parameters of the gully structure at different areas was analyzed. The gully fractal dimension showed a significant numerical difference in different areas, whereas the variation of the gully branch ratio was small. The change rule indicated that the development degree of the gully obviously varied in different regions, but the morphological structure was basically similar.
The previous geological research work in the Yangtze River Economic Zone is systematically summed up and arranged in this paper. Resources and environment conditions and major geological problems which have aroused much attention in the construction and the territorial planning in the Yangtze River Economic Zone are studied. The research results show that the resource conditions of cultivated land, shale gas, geothermal resources, llithium etc. are very favorable in the Yangtze River Economic Zone: 30 million hmJ farmlands without heavy metal pollution exhibit concentrated distribution; there are three national shale gas exploration and development bases with explored reserves of 544.1 billion cubic meters; available geothermal resources amount to 240 million tons of standard coal per year, equivalent to 19% of the amount of coal consumption in 2014; the largest energy lithium metal ore deposit in Asia was found; resources and environment conditions are favorable for the development of modern agriculture industry, clean energy and strategic emerging industries. Nevertheless, in some parts of the Yangtze River Economic Zone, there exist some major geological problems such as active faults, karst collapse, ground subsidence, and landslide-collapse-debris flow, which affect the river- crossing channels, high- speed railway, urban groups and green ecological corridor planning and construction. The authors point out that these problems deserve much attention. For this, the relevant suggestions and countermeasures are put forward. At the same time, the paper puts forward the idea of further supporting the development of the Yangtze River Economic Zone. © 2017 Editorial Board of Geology in China. All rights reserved.
Long profiles of rivers provide a platform to analyse interaction between geological and geomorphic processes operating at different time scales. Identification of an appropriate model for river long profile becomes important in order to establish a quantitative relationship between the profile shape, its geomorphic effectiveness, and inherent geological characteristics. This work highlights the variability in the long profile shape of the Ganga River and its major tributaries, its impact on stream power distribution pattern, and role of the geological controls on it. Long profile shapes are represented by the sum of two exponential functions through the curve fitting method. We have shown that coefficients of river long profile equations are governed by the geological characteristics of subbasins. These equations further define the spatial distribution pattern of stream power and help to understand stream power variability in different geological terrains. Spatial distribution of stream power in different geological terrains successfully explains spatial variability in geomorphic processes within the Himalayan hinterland area. In general, the stream power peaks of larger rivers lie in the Higher Himalaya, and rivers in the eastern hinterland area are characterised by the highest magnitude of stream power.
Heavy mineral and detrital magnetite geochemistry were analyzed to extract sediment provenance indexes from different reaches of the modern Yangtze River which were used to trace sediment source of the Yangtze Delta and to speculate its geomorphology change since the Pliocene. Our results show that diagnostic heavy minerals of the upper Yangtze sediment are characterized by clinopyroxene (12% on average) and magnetite (7% on average); the middle reaches by ilmenite, zircon and tourmaline; and the local small rivers by fluorite. Detrital magnetite composition of Ti, Mg, V and Cr is high in the upper Yangtze from the underlying basalt. These diagnostic indexes are then used in the Pliocene sediment core to extract provenance signal of different Yangtze reaches. Analysis of core sediment of the Yangtze Delta reveals that sediment provenance of the Pliocene was from local small rivers. Since the beginning of the Pleistocene, core sediments provenance was similar to that of the middle Yangtze tributaries. After 1.2 Ma, high content of pyroxene and magnetite grains that are rich in Ti, Mg, V, Cr imply sediment provenance signals from the upper Yangtze. Sediment provenance shift from short-distance sources to more distant sources indicates that the geomorphology of the Yangtze Delta region has undergone a great transformation since the Pliocene. This dramatic landform change is likely in response to continuous uplift of the Tibetan plateau and accelerated subsidence of the east China coast since the Pliocene.
As a composite orogenic belt of the Himalaya giant orogenic zone, Yidun arc, Sanjiang region (means three rivers region, i.e.: Jinsha River, Nujiang River and Lancang River), experienced an evolution history including Indosinian subduction orogeny of oceanic crust, Yanshanian arc-continental collision orogeny and Himalayan intra-continental strike-sliding shearing. Probably due to different subduction dipping degrees, the Yidun old arc belt of late Triassic (206-237 Ma) has a different development history in its northern and southern segments. Changtai arc in the northern segment was characterized by intra-arc rift with expanding nature and developed a fluid convergent ore-foming system in an extentional environment, which formed. VMS-type Zn-Pb-Cu deposits and epithermal Ag-Au-Hg deposits. Zhongdian arc of the southern segment lacked back-arc basin, but had extensive calc-alkaline complex distribution of arc volcanics-porphyry-porphyrite, which formed porphyry-skarn-type Cu-polymetalic deposits. During the arc-continental Collisional process of Triassic-Jurassic boundary, early continental plate subduction led to formation of syn-collisional granites (200 Ma). Whereas, late post-orogenic extention resulted in intrusion of A-type granites (75-138 Ma), which was accompanied by development of convergent magma-fluid ore-forming system under an extensional regime and formation of skarn-type tin deposits and fault-controlled hydrothermal Ag-polymetallic deposits. Strong lithospherical shearing and thrusting resulted from Yangtz continental plate subduction caused develorment of a convergent fluid system under a compressional-shearing environment and formation shearing-type Au deposit in the Garze-Litang ophiolitic melange zone. The effect of the Indian-Asian continental collision on the Yidun arc zone was mainly manifested in intra-continental strike-sliding process and alkaline grainte and porphyry intrusion (50-30 Ma). The latter brought us porphyry Au deposits.
Studies suggest that at least four stages of regional-scale tectonic and magmatic events have taken place in the South China block, namely, geodynamic processes of Neoproterozoic and Late Mesozoic active continental margins, Early Paleozoic and Early Mesozoic intracontinental orogenies. The Cathaysia block was a pre-Nanhua basement consisting mainly of Neoproterozoic rocks instead of a stable old land. It experienced a complex evolution from assembly through break-up to re-assembly. The intracontinental shortening during Silurian led to the stabilization of the united South China continent. The entire South China Block was under a shore-shallow sea-slope setting, with no translithospheric fault, no regional-scale volcanism and mantle-derived magmatism in the period from Sinian to Jurassic, during which polyphase tectonic and magmatic events occurred in the united South China lithosphere. It evolved into a part of the Late Mesozoic Western Pacific active continental margin after the Early-Middle Jurassic transformation from Tethysian to Pacific tectonic regimes. The South China lithosphere experienced polyphase continental growth due to the dominant lateral accretion of block assembly accompanied by vertical growth of magma up-swarming. During the Cretaceous, the South China basin and range tectonics occurred in the western shore of the Pacific Ocean due to strong intracontinental extension caused by the northwestward subduction of the Pacific Ocean. Long-term intraplate tectonism and polystage granitic magmatism provided South China with a favorable condition of metallization, forming various large-size ore deposits and resources. Neoproterozoic Nanhua Period and Early Cretaceous were two dominant stages of metallization, with various types of ore deposits being chiefly formed in the Early Cretaceous period.
Morphological evidence for ancient channelized flows (fluvial and fluvial-like landforms) exists on the surfaces of all of the inner planets and on some of the satellites of the Solar System. In some cases, the relevant fluid flows are related to a planetary evolution that involves the global cycling of a volatile component (water for Earth and Mars; methane for Saturn’s moon Titan). In other cases, as on Mercury, Venus, Earth’s moon, and Jupiter’s moon Io, the flows were of highly fluid lava. The discovery, in 1971, of what are now known to be fluvial channels and valleys on Mars sparked a major controversy over the role of water in shaping the surface of that planet. The recognition of the fluvial character of these features has opened unresolved fundamental questions about the geological history of water on Mars, including the presence of an ancient ocean and the operation of a hydrological cycle during the earliest phases of planetary history. Other fundamental questions posed by fluvial and fluvial-like features on planetary bodies include the possible erosive action of large-scale outpourings of very fluid lavas, such as may have produced the remarkable canali forms on Venus; the ability of exotic fluids, such as methane, to create fluvial-like landforms, as observed on Saturn’s moon, Titan; and the nature of sedimentation and erosion under different conditions of planetary surface gravity. Planetary fluvial geomorphology also illustrates fundamental epistemological and methodological issues, including the role of analogy in geomorphological/geological inquiry.
The ability to understand gully erosion development is closely related to our ability to quantify the morphology of gullies. At present, various technologies are at hand to collect data at increasing levels of detail. However, many of the developed technologies are time-consuming, difficult to apply or expensive. As an alternative, image-based modelling offers a cost-efficient, flexible and rapid method to quantify gully morphology from photographs taken in the field. In this study, the use of image-based modelling was tested and fine-tuned to quantify the morphology of four gully heads in contrasting biophysical environments prone to gully erosion: two bank gullies in Central Belgium and two permanent gullies in Northern Ethiopia. Ground photographs (n = 88–235) were taken with a reflex Canon EOS 450D camera having a 20 mm wide-angle lens with a fixed focal length. The data collection occurred during days of 30–100% cloud cover and after removing excessive vegetation in the gullies. Processing of the photographs occurred in PhotoScan 1.0.2. software using the semi-automated Structure from Motion–Multi View Stereo (SfM–MVS) workflow, and allowed to produce 3D Digital Elevation Models with accuracies that range from millimetres to centimetres. In addition, for the same surface, 2.5D models were created in ArcGIS. Gully morphological properties were derived and included cross-sections, total volume and volume of undercut walls and soil pipe inlets. For the volume calculation, OPTOCAT software was used. Cross-sections were also quantified by tape meter measurements. When compared to 3D models, cross-sections quantified from tape meter measurements and from 2.5D models underestimate the cross-sectional area by < 1–14% and 0–2.5% respectively. Considering gully volume, 2.5D and 3D approximations show only small differences, related to the volume of soil pipe inlets and undercutting areas. These differences, however, highlight the erosive activity of the gullies, and are important to understand gully dynamics in detail. Geomorphologically speaking, areas where undercutting or soil piping occurs are among the most dynamic and reveal where important morphologic changes are about to occur. The accuracies reported in this study are similar to those obtained in other studies that consider surfaces of similar scales. In sum, image based modelling is a promising tool to study in detail gully morphology in 3D, which is the closest approximation of the surface morphology.
The fluvial riparian and aquatic patch mosaic varies along rivers according to geomorphological setting, hydrological regime, sediment supply and surface–groundwater connectivity. This relation between physical processes and plants is not unidirectional. Once established, riparian and aquatic plants frequently act as physical ecosystem engineers by trapping and stabilising sediments, organic matter and the propagules of other plant species, modifying the local sedimentary and morphological environment by driving the development of landforms and associated habitats, and so facilitating the rapid establishment of other plants that can in turn reinforce the development of landforms such as river banks, vegetated islands and floodplains. This paper reviews knowledge on the hydrogeomorphological significance of riparian and aquatic vegetation with a particular emphasis on humid temperate, mixed load, gravel bed, floodplain rivers.
We collected riverbed sediments of the headwaters of the Yangtze River (Chumaer River, Tuotuo River, Gaerqu River and Buqu River), Tongtian River and Jinsha River (HTJR) flowing on the eastern Tibetan Plateau and analyzed their mineralogical features, major and trace element contents. The results show: (i) very poor correlations of Na2O, K2O, CaO, Ba, and Sr to SiO2, LREE to Th, HREE to Hf, and Ta/La to Ti, and characteristics of Eu anomaly (the ratios of (Eu/Eu*)N range from 0.60 to 0.83 with an average value of 0.71) all indicate that the Jinsha River sediments have not undergone much mineralogical sorting; (ii) illite and chlorite are predominant clay minerals, and quartz, calcite, dolomite, albite, and K-feldspar are prevailing non-clay minerals. The characteristics of mineral assemblage indicate relatively weak chemical weathering degree in these river basins; (iii) very high contents of Fe2O3, MgO, TiO2, Sc, V, Cr, Co, and Ni at Panzhihua mainly result from the huge-sized V–Ti magnetite deposits occurred in layered gabbroic intrusion; and (iv) the chemical alteration index (CIA) in the HTJR ranges from 46.5 to 69.2 and with an average value of 60.5 which indicates relatively weak weathering degree.