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Severe soil erosion occurs on the Loess Plateau in China, which makes the Yellow River the most sediment-laden river in the world. Construction of about 60,000 sediment check dams has remarkably controlled soil erosion on the Loess Plateau and reduced the sediment load of the middle and lower Yellow River. Nonetheless, little is known about the mechanism of erosion control and vegetation development of sediment check dams. The function of a single check dam mainly is trapping sediment, while the function of a train of check dams comprising dozens of or over hundreds of check dams in a gully encompasses controlling bed incision and reducing erosion energy. A formula was proposed to calculate the potential energy of bank failure and slope failure in a gully, which essentially constitutes the erosion energy. The erosion energy increases when gully incision occurs, which is induced by the incision of the Yellow River and its tributaries on the Loess Plateau. Sediment deposition in many gullies due to construction of check dams reduces the erosion energy to almost zero, which in turn greatly reduces soil erosion and sediment yield. Construction of check dams promotes vegetation development. The vegetation-erosion dynamics model was used to study the effect of check dams on vegetation development. Simulation results show that reforestation without check dam construction might result in an increase of vegetation cover in the first ten years and then a drop of vegetation cover to less than 10% in the later years. The check dams provide a foundation for vegetation development.

Hyperconcentrated flows often occur in the middle and lower Yellow River (MLYR) and its tributaries, within which the main sediment source originates from the Loess Plateau of China due to serious water erosion. Little is known about the properties of river sediment that is transported by hyperconcentrated flows, particularly with respect to the mineral composition and size distribution. Samples of sediment and loess were collected in the northern, middle, and southern Loess Plateau and the mainstream and tributaries of the MLYR. A total of 18 loess samples and 24 river sediment samples were analyzed to determine their sediment size distribution and mineral composition. The bottom loess samples reflected the original sedimentary features of the Loess Plateau, and the median particle size reduced, and the clay content increased from the north to the south of the study region. The surface loess has been weathered under the action of wind and rainfall, and the clay particle content in the surface loess samples was higher than that in the undisturbed bottom loess. Erosion of the surface soil due to rainfall and surface runoff means that fine particles (mostly clay) have been washed away. The median diameter of surface loess particles was a little larger than that of the bottom loess particles where water erosion dominates. The particle size became coarser with increasing distance from the estuary in the MLYR, which reflects depositional sorting in the river channel. Significant logarithmic relations were found between the median diameter of the sediment particles and the i) non-clay mineral content and ii) clay mineral content. Thus, clay and non-clay mineral compositions can be conveniently estimated from the particle size distribution.

The fluvial geomorphology in tectonically active (particularly rapid uplift) regions often undergoes continuous change. The rapid uplift is coincident with high erosion rates; consequently, incised valleys are formed. Mass flows (for example, avalanches, landslides, and debris flows) in incised valleys can markedly influence fluvial processes and even reshape valley geomorphology. However, these processes and long-term evolution corresponding to mass flows require further clarification. Field campaigns were carried out in the region near the Yigong Tsangpo and Palong Tsangpo Rivers (hereafter the Yigong and Palong Rivers), the two largest tributaries of the lower Yarlung Tsangpo River, to examine the feedback between fluvial processes and mass flows. Remote sensing images from recent decades were used to compare the channel morphology before and after typical mass flows (particularly catastrophic ones). The morphology of the lower Yigong River has evidently been impacted by landslides, while that of the Palong River has mainly been shaped by glacial processes and debris flows. At present, the morphology of the latter consists of alternating sections of gorges and wide valleys, with a staircase-like longitudinal profile. The gorge sections exhibit single and deeply incised channels with a high-gradient channel bed and terraces. In contrast, the wide valley sections consist of lakes, braided or anabranching channels, gentle bed gradients, and thick alluvial deposits. Debris flows occur more frequently in gullies in the reaches of the gorge sections and rarely in gullies along the wide valley sections. The occurrence of mass flow events has resulted in an imbalance of the previous (quasi-)equilibrium in the river morphology; however, this has triggered negative feedback that is driving the transient river morphology to a new state of (quasi-)equilibrium.

Anthropogenic impacts and climate change modify instream flow, altering ecosystem services and impacting on aquatic ecosystems. Alpine rivers and streams on the Qinghai-Tibet Plateau (QTP), are esp...

Uplift of the Qinghai-Tibetan Plateau has resulted in rapid incision of rivers along the margin of the plateau. Landslides occur frequently as a consequence of increasing bank slope and potential landslide energy due to stream bed incision or lateral bank erosion on the concave banks at bends. The Fencha Gully is on the eastern margin of the Qinghai-Tibetan Plateau and is developing on a huge landslide body. Flume experiments were conducted on the base of the field investigation to study the mechanism of landslides induced by stream bed incision. The experiments were designed with a length scale ratio of 1:20. Landslides and stream bed incision with loose sediment were observed and analyzed. The results show that landslides are induced as a result of stream bed incision. The potential landslide energy is defined, which increases quickly with an effective incision depth coupling vertical incision and lateral bank erosion. The occurrence of landslides can be attributed to increasing incision depth and potential landslide energy. Results indicate that the critical effective incision depth is 4.0–6.0 m. A critical value of the potential landslide energy is found from the experiments. Landslides occur if the potential energy exceeds the critical energy, which is 2.24×104 t·m/s2 for the Fencha Gully. The incision depth and potential energy of landslides from the Fencha Gully agree well with the results.

Throughout the history of China, the Yellow River has been associated with flood disasters and changes in the course of its lower reaches because of sedimentation. From 602 B.C. to 1949 the river experienced 1593 levee bursts, flooding vast areas, and claiming millions of human lives. The river shifted its main course by avulsion 26 times with the apex around Zhengzhou, resulting in devastating calamities and numerous old channels. Training of the Yellow River has a history of more than 3000 yr. Levee construction has been the major strategy for flood control. Two extremely different strategies has been proposed and practiced in the past 2000 yr, i.e. the “wide river and depositing sediment” strategy and the “narrow river and scouring sediment” strategy. This paper analyzes the levee breaches and flood disasters in the past 2000 yr and compares the results of the two extremely different strategies. The “narrow river and scouring sediment” strategy has only short term effects on levee breach control and flood mitigation. The “wide river and depositing sediment” strategy can essentially mitigate flood disasters and reduce levee breaches for a long term period of time. The “wide river and depositing sediment” strategy has been used and no levee breach has occurred in the past 67 yr, which has been the only periods of more than 50 yr with no levee breaches in the history of the Yellow River since 700 A.D. Modern flood and sedimentation management methods have also been introduced, and the strategy of applying the ‘“widen the river and enhance the levees” approach for the upper and lower reaches management is proposed.

The paper studies the stochastic nature of sediment transport in rivers. Sediment transport formulas are valid only for prediction of average sediment transportation over long reaches of rivers and long periods of time. However, flow in rives is unsteady and non-uniform and failures of hydraulic works may occur because of instantaneous and local behaviour of sediment movement. An experimental study demonstrates fluctuation of the bed load transportation, which is so obvious that the maximum instantaneous transport rate is higher than 3 times of the average and the minimum is less than 5% of the average. In the upper Yangtze River, broad and shallow sections are between narrow and deep sections. Different from the normal law sediment transportation in broad sections exhibits high transport rate in low flow and low rate in high flow. Qb is approximately inversely proportional to Q. Gravel bed load moves along a so called conveying belt and there is almost no bed load movement outside of the belt. The phenomenon was investigated in a scale model and the results shows the conveying belt is relatively fixed and is of only 10% of the total width of the channel bed.

An investigation on 152 gullies along the Daheba River in the Tongde sedimentary basin was performed. Debris flows develop in gullies with an excess topography ZE, which represents the sediment availability, above a critical threshold value. Debris flows in the Daheba watershed are supply-unlimited, i.e sediment is abundantly available from the steep erodible gully banks. Debris flows consist of a head and a body. The body propagates faster than the head and constantly supplies it with sediment. The body and head propagate in an intermittent way through the transient storage of sediment on the riverbed and its subsequent remobilization. Although the main sediment supply is provided by bank collapse, debris-flow events also incise the gully bed. The growth and incision of debris-flow gullies in supply-unlimited watersheds is mainly controlled by the frequency of occurrence of debris flows, which is closely related to ZE. With growth of the gully drainage area, ZE and the debris-flow frequency initially increase, until they reach maximum values in gullies with a drainage area of intermediate size, which are assumed to be the morphologically most active gullies. With further growth of the gully drainage area, ZE and the debris-flow frequency decrease, which opposes the development of debris flows and leads to a more stable gully morphology.

The Yarlung Tsangpo River, which flows from west to east across the southern part of the Tibetan Plateau, is the longest river on the plateau and an important center for human habitation in Tibet. Suspended sediment in the river can be used as an important proxy for evaluating regional soil erosion and ecological and environmental conditions. However, sediment transport in the river is rarely reported due to data scarcity. Results from this study based on a daily dataset of 3 years from four main stream gauging stations confirmed the existence of great spatiotemporal variability in suspended sediment transport in the Yarlung Tsangpo River, under interactions of monsoon climate and topographical variability. Temporally, sediment transport or deposition mainly occurred during the summer months from July to September, accounting for 79% to 93% of annual gross sediment load. This coincided with the rainy season from June to August that accounted for 51% to 80% of annual gross precipitation and the flood period from July to September that accounted for approximately 60% of annual gross discharge. The highest specific sediment yield of 177.6 t/km2/yr occurred in the upper midstream with the highest erosion intensity. The lower midstream was dominated by deposition, trapping approximately 40% of total sediment input from its upstream area. Sediment load transported to the midstream terminus was 10.43 Mt/yr with a basin average specific sediment yield of 54 t/km2/yr. Comparison with other plateau-originated rivers like the upper Yellow River, the upper Yangtze River, the upper Indus River, and the Mekong River indicated that sediment contribution from the studied area was very low. The results provided fundamental information for future studies on soil and water conservation and for the river basin management. Copyright © 2017 John Wiley & Sons, Ltd.

Hydraulic geometry (HG) is an important geomorphic concept that has played an indispensable role in hydrological analyses, physical studies of streams, ecosystem and aquatic habitat studies, and sedimentology research. More than 60 years after Leopold and Maddock (1953) first introduced the concept of HG, researchers have still not uncovered the physical principles underlying HG behavior. One impediment is the complexity of the natural river cross section. The current study presents a new way to simplify the cross section, namely, the hydraulic equivalent section, which is generalized from the cross section in the “gradually varied flow of an alluvial river” (GVFAR) and features hydrodynamic properties and bed-building laws similar to those of the GVFAR. Energy balance was used to derive the stage Z-discharge Q relationship in the GVFAR. The GVFAR in the Songhua River and the Yangtze River were selected as examples. The data, including measured discharge, river width, water stage, water depth, wet area, and cross section, were collected from the hydrological yearbooks of typical hydrological stations on the Songhua River and the Yangtze River from 1955 to 1987. The relationships between stage Z-discharge Q and cross-sectional area A-stage Z at various stations were analyzed, and “at-a-station hydraulic geometry” (AHG) relationships were obtained in power-law forms. Based on derived results and observational data analysis, the Z-Q and Z-A relationships of AHG were similar to rectangular weir flows, thus the cross section of the GVFAR was generalized as a compound rectangular, hydraulic equivalent cross section. As to bed-building characteristics, the bankfull discharge method and the stage-discharge-relation method were used to calculate the dominant variables of the alluvial river. This hydraulic equivalent section has the same Z-Q relation, Z-A relation, dominant discharge, dominant river width, and dominant water depth as the cross section in the GVFAR. With the hydraulic equivalent section, the relationships between the discharge and river width, river depth, and width-to-depth ratio are easier to depict in DHG analysis. Replacement of the cross section in the GVFAR with the hydraulic equivalent section is expected to promote further development of HG.

This situated case study outlines how a place-based landscape template provided an integrative platform for the environmental arm of a cross-disciplinary international education initiative, the Three Brothers Project, wherein geographers at the University of Auckland worked alongside engineers at Tsinghua University in Beijing to support collaborative research with grassland and agricultural scientists at Qinghai University in western China. These collaborative efforts built upon strategic leadership at government and university level, an appropriate resource base and engaged practitioners who developed and embedded research opportunities that built upon a shared commitment to research on environmental values in the source zone of the Yellow River. We highlight how a landscape framing brought together divergent mindsets, methodologies and practices in this collaborative research, providing an effective platform to share experiences, discuss perspectives and develop research outcomes.

Controlling desertification is an important ecological target for the Qinghai-Tibet Plateau of China, where studies on impacts of vegetation restoration measures on sandy soil improvement are still lacking. The Mugetan Desert in Guinan County, Qinghai Province, northeastern Qinghai-Tibet Plateau is a representative ecological restoration area. The impacts of artificial vegetation on the ecological restoration and its properties are studied by using field investigation and sample testing including contents of the surface layer and the vegetation composition of movable, semi-fixed, and fixed sand dunes. Results demonstrate that the moss crust has formed on the surface of a sand dune which has become fixed after 30 years under the impact of artificial vegetation (i.e. Cathay poplar). Meanwhile, the clay minerals, organic matter, and other soil available nutrients have markedly increased. A correlation has been found between these materials, i.e., clay minerals and organic matter content increasing with silt and clay increases with reduction in sand content. In addition, soil nutrient were positively correlated with the increase of plant diversity.Under the current meteorological conditions, the artificial vegetation is helpful for the stabilization of sand dune and the ecological restoration in the Mugetan Desert.

Assemblage structures and distribution patterns of aquatic macroinvertebrates are influenced by riverine environmental variables. The relationship between environmental variables and macroinvertebrate assemblages, however, has rarely been examined quantitatively for rivers with high stream power at high altitude. In this study, stream power was analyzed in relation to macroinvertebrate distributions in the Yarlung Tsangpo River Basin on the Tibetan Plateau. Field investigations were carried out at 22 sites in April, 2014 and 2015. Stream power, substrate size and evenness, discharge, bedload transport, and organic detritus availability varied greatly among these sites. In total, 125 taxa of macroinvertebrates belonging to 48 families and 104 genera were identified. The macroinvertebrate density was negatively and significantly correlated with the stream power (D = 3.30, P < 0.001). Both the assemblage indices (taxa richness, density, biomass, and the Improved Shannon–Wiener Index) and the environmental variables (elevation, substrate size, and discharge) differed among the sites with different levels of stream power. An adaptability analysis showed contrasting adaptive strengths of typical taxa. Orthocladius, Baetis, and Simulium adapted to wide ranges of stream power and their most optimal stream powers were relatively high, while Bethbilbeckia and Natarsia were only well-adapted to fairly narrow ranges in stream power. Some macroinvertebrates have evolved specific strategies to adapt to high stream power: Baetidae and Heptageniidae have developed specialized body shapes, and Epoicocladius has altered its host preference. The stream power has been shown to be significantly correlated with and could be used to predict macroinvertebrate density in the Yarlung Tsangpo River Basin.

•Meandering channel develops in a hyper-arid environment of the Tarim River, Northwestern China.•The planform of meandering channel in the Tarim River are similar to those in other environments.•The migration rates with wider range are higher than the meandering rivers in other environments.•Significant bank erosion occurs mainly during floods, which results in high migration rates and frequent cutoffs.

The biodiversity value of river-oxbow lake systems in high plateau peatland has been little recognized, and there are many gaps in our understanding of their ecology. In this study, we investigated the river-oxbow lake system of the Bai River basin, the main tributary of the Yellow River Source in the Zoige wetland from 2015 to 2016, in attempt to show how the environmental variations, especially hydrological connectivity and macrophyte biomass in the river-oxbow lake system influenced macroinvertebrates. Habitat patches were investigated in 11 river cross-sections and 18 oxbow lakes in the Bai River basin. Through hierarchical clustering and non-metric multidimensional scaling, four main types of habitats were identified in the river-oxbow lake system in the plateau: sand-bed river, cobble-bed river, sparse-macrophyte oxbow lake, and luxuriant-macrophyte oxbow lake. The luxuriant-macrophyte oxbows were characterized by high dissolved oxygen concentrations, alkalinity, and higher macroinvertebrate richness, density, biomass, and the Improved Shannon-Wiener Index in comparison to the other habitat types. Additionally, influential patterns of environmental variables on macroinvertebrates were analyzed using redundancy analysis. Lasso regression models were established to describe how macroinvertebrate density responded to macrophyte biomass and other variables, and how macrophyte biomass responded to hydrological connectivity and oxbow size. It was revealed that reduced hydrological connectivity and reduced oxbow size played important roles in increasing the biomass of submerged macrophyte, and dense macrophyte was directly responsible for the high biodiversity of macroinvertebrates. Different from the commonly believed unimodal influential pattern that medium hydrological connectivity supports the highest biodiversity in oxbow lakes reported in previous studies, macroinvertebrates in the high plateau river-oxbow lake systems benefited from low connectivity and reduced size. Oxbow lakes, especially those covered with luxuriant macrophytes, diversified the macroinvertebrate assemblages and enhanced primary consumer biomass at the regional scale.

Observations from field investigations showed that flow velocity greater than 3 m/s rarely occurs in nature, and high flow velocity stresses the bio-community and causes instability to the channel. For alluvial rivers without strong human disturbance, the flow velocity varies within a limited range, generally below 3 m/s, while the discharge and wet area may vary in a range of several orders. This phenomenon was studied by analyzing hydrological data, including daily average discharge, stage, cross sections, and sediment concentration, collected from 25 stations on 20 rivers in China, including the Yangtze, Yellow, Songhua, Yalu, Daling, and Liaohe Rivers. The cross-sectional average velocity was calculated from the discharge and wet area using the continuity equation. For alluvial rivers, the wet cross section may self-adjust in accordance with the varying flow discharge so that the flow velocity does not exceed a limit value. In general, the average velocity increases with the discharge increase at low discharge. As the discharge exceeds the discharge capacity of the banks, any further increase in discharge does not result in a great increase in velocity. The average velocity approaches an upper limit as the discharge increases. This limit velocity, in most cases, is less than 3 m/s. Human activities, especially levee construction, disturb the limit velocity law for alluvial rivers. In these cases, the average velocity may be approximately equal to or higher than the limit velocity. The limit velocity law has profound morphological and ecological implications on alluvial rivers and requires further study. Rivers should be trained and managed by mimicking natural processes and meeting the limit velocity law, so as to maintain ecologically-sound and morphological stability.

Bed structures develop in many coarse gravel-bed rivers, and the distribution of bed structures is obviously impacted by the environment conditions, especially hydrology and sediment regimes. This study carried out field investigations in natural tributaries of the Yangtze River to study the sizes of bed structures, their distribution in the basin, as well as their connections with local hydrology and sediment regimes. A field experiment was also conducted to study the evolution and functions of bed structures. Results of both the investigations and experiment indicated that under the conditions of low bedload, the structure intensity is in a positive correlation with the unit-width stream power, which is consumed by bed structures when the river is in a dynamic equilibrium. If the structures are not able to dissipate the whole energy, the river status turns into disequilibrium and the riverbed would be eroded by excess energy, and the river system would move to a stable position on the structure-power equilibrium line. The fluvial morphology of coarse-grained riverbeds is controlled by this mechanism to some extent. Sometimes excess energy can be consumed by bedload transport even with insufficient structure intensity, thus a unified power consumption model including bedload is also discussed.

Rivers have many service functions, and play an important role in people's living and agricultural production. During the last decades, intensive human activities have been threatening river ecosystem. For shipping, hydraulic engineering facilities (e.g. spur dikes) have been built along river bank to increase water depth. However, natural habitat conditions (i.e. substrate, flow regime, water physico-chemical properties) are accordingly altered. Therefore, it is necessary to select representative organisms as indicators to assess the aquatic ecological status of different habitat conditions, furthermore, management strategies are to be put forward. Macroinvertebrates are often considered as good indicators of long-term changes in environments due to their confinement to the bottom, long life cycles and limited abilities of movement. In this study, field investigations of macroinvertebrates in the West River were conducted in November 2009 (at low water level) and May 2010 (at high water level). Altogether 70 taxa of macroinvertebrates belonging to 30 families and 59 genera were identified. Among them were 16 annelids, 21 mollusks, 32 arthropods and 1 miscellaneous animal. The average density and biomass of total macroinvertebrates were 140 ind m −2 and 0.23 g dry weight m −2 , respectively. Canonical Correspondence Analysis (CCA) revealed that major factors structuring macroinvertebrate assemblages were flow velocity ( U ), water depth ( Z ), conductivity (Cond), total nitrogen (TN) and substrates (clay, silt, cobbles and bedrock). Density and diversity of macroinvertebrates peaked in the cobbles, while biomass reached the maximum in the bedrock. It is indicated that stable and heterogeneous habitats were beneficial to development of benthic assemblages. To conserve these habitats, type and construction position of spur dikes should receive enough attentions. Thus, it is suggested that as few spur dikes as possible can be constructed in the riverbed covered with cobbles and bedrocks. Otherwise, the angle between spur dike and river bank need be analyzed to generate the appropriate flow regime which can prevent the stable substrates from being buried by sands. Some advice about length and separation distance of spur dikes is also presented.

Highland running-water biodiversity has gained growing interest around the world, because of the more pristine conditions and higher sensitivity to environmental changes of highland rivers compared to the lowland rivers. This study presents the findings of systematic investigations and analyses on running-water biodiversity of macroinvertebrate assemblages in the most important headwater streams in the Yalutsangpo and Sanjiangyuan River basins in the Qinghai-Tibet Plateau and the lowland headwaters of the Songhua River, Juma River, and East River during the non-flood seasons of 2012 to 2016. The results indicated that the headwaters on the plateau had a higher regional biodiversity compared to the lowland rivers with the similar flow and substrate conditions. Even though the local diversity of the highland rivers was not significantly different at each single site, the taxonomic composition was significantly different with several rarely seen species scattering among the different sites, resulting in a high regional biodiversity. The biodiversity and composition of macroinvertebrates were strongly affected by the altitude gradient and the environmental variables associated with altitude. To be specific, for the Yalutsangpo River, canonical correspondence analyses of the macroinvertebrate assemblages and their environmental variables indicated that altitude, stream condition (represented by river pattern, riverbed structures, substrate composition), and water temperature influence macroinvertebrate taxa composition. Because of the restrictive plateau conditions including low water temperature, poor aquatic and riparian vegetation, and low runoff, the macroinvertebrate assemblages showed low biodiversity and were vulnerable to potential human disturbance/climate change. Therefore, it is essential to conserve suitable conditions of the determinative environmental variables to protect the unique and high regional biodiversity of the headwaters on the Qinghai-Tibet Plateau.

In recent years, flash flood disasters have occurred frequently in southwest China due to the increased frequency of extreme climate events. To solve this problem, great efforts have been made in studying the process of flash flood. However, little attention was paidon bearing body of hazard, the clusters of buildings. Thus the real disaster mechanism of flash flood remains unclear. Accordingly, based on the experiments of artificial flash floods in a conceptual solid model, this paper focuses on the flood-impacted inundation characteristics of the building clusters at different locations of the gully model, in order to obtain a better understanding of the disaster process and the interaction between the flash floods and building clusters. The results showed that, in a typical small-scale flash flood gully with hot and dry climate, 1) clusters of buildings on an alluvial fan could reduce about 35% of the flooding area by blocking the diffusion of the flood to the depression areas, and could also promote the deposition in lower reaches of the river channel by blocking the overbank flow from going back into the channel, making the width-depth ratio of the channel larger. 2) The flash flood rates of disaster and hazard on the alluvial fan are generally higher than that of the inner gully. For the inner gully, buildings located on the beaches along the lower river and the transitional areas of the straight channel and channel bends can easily be affected because of their lower elevations. For the alluvial fan, buildings nearby the meanders suffer the greatest impacts because of bank collapsing and flooding. 3) The safe vertical distance from a building to the river channel is 13 m for the buildings in the inner gully under extreme floods. Below this threshold, the smaller the vertical distance is, the greater the risk exposure is. For the buildings on the alluvial fan, especially for the buildings near the concave bank of the top rush point, the horizontal distance is more important, and the safe value is 80 m under extreme floods.

The golden mussel Limnoperna fortunei (Dunker, 1857) is a filter-feeding species of freshwater bivalve that is native to southern China. The species readily invades water transfer tunnels, causing considerable damage. The mussels typically attach to the walls of pipelines and gates, and are associated with serious biofouling. This may lead to increased flow resistance of the tunnels and to corrosion of their walls, and may threaten their operation. The mussels exhibit very high environmental adaptability and, once they become established in the water transfer works, they are impossible to eliminate. Therefore, prevention of the entry of golden mussels into the tunnels is considered to be the most efficient means of avoiding biofouling by this species. The main period of invasion corresponds with their reproductive season, which therefore forms the focus of prevention methods. Consequently, further study of reproduction of the golden mussel is essential. The process of attachment of golden mussels to material with a solid surface was studied experimentally in the Xizhijiang River, a tributary of the East River. It is the main water resource of the water transfer project supplying Shenzhen and Dongguan, southern China. Experiments were conducted from March 2010 to April 2011. Fourteen sets of materials were installed in the river to monitor attachment of the mussels. Shell-length frequency data of golden mussels attached on the monitoring materials were determined monthly and analyzed for identification of cohorts of individuals produced during successive reproductive seasons, and for measurement of their growth rates. The Windows version of FiSAT (FiSAT II), a software package developed specifically for the analysis of length-frequency data of aquatic biota, was applied in this study. The density of attachment of golden mussels to the monitoring materials was related to the water depth and to the orientation of the attachment surface. Clay and silt precipitation reduced the attachment density of the mussels. The attachment density on downward facing surfaces with lower sediment precipitation was much higher than the density on the upward facing surfaces with higher precipitation. A six-fold increase in precipitation of clay and silt was associated with a 90% decrease in attachment density. The analysis of monthly shell-length frequency indicated that the mussels produced three generations per year, each of which was associated with two reproductive peaks, resulting in six cohorts per year. The growth rates of the six cohorts differed and varied from month to month. Mean growth rates were in the range 0.4–3.5 mm/month. The average growth rate was logarithmically related to the water temperature, total nitrogen and total phosphorus concentrations. Therefore, the time for the cohorts to reach maturity (shell length: 6–8 mm) varied with these environmental parameters. The feasibility of preventing the attachment of golden mussels is discussed. Intensive prevention efforts should be performed during their peak reproductive seasons (March to May, June to September, and October to December). Clay or silt precipitation is recommended as a potential method for preventing the attachment of golden mussel to materials. However, because of the extended and frequent reproductive activities of golden mussels, preventing their invasion of water transfer tunnels remains a challenge; control strategies will need to be applied for long periods.

The fluvial process of the Yalu Tsangpo River occurs concurrently with the uplift of the Qinghai-Tibet Plateau. Therefore, the river exhibits unique features in morphology and sediment deposition. Field investigations were performed from 2009–2011 and the depth of the interface between the sediment deposits and bed rock was detected with an electromagnetic imaging system (EH4) at 29 cross sections. Sediment deposits were sampled along the Yalu Tsangpo valley from Xietongmen to the Yalu Tsangpo Canyon. The results show that a huge amount of sediment has been deposited in four wide valley sections because the uplift rate in these sections was lower than that in the downstream gorge sections over the past million years. About 518 billion m3 of gravel and sand have been stored in the high mountain river valleys, which has changed the V-shaped mountain river valley into a U-shaped wide river valley in the four sections. In the sections with high uplift rates the river bed is incised and has formed gorges and the Yalu Tsangpo Canyon.

The Ruoergai Swamp (Zoige) at the eastern margin of the Qinghai-Tibet Plateau in western China is the world's largest plateau peat wetland. Rapid shrinkage of the swamp since the 1950s has endangered the local terrestrial and aquatic ecosystems and the water supply of the upper Yellow River. The causes of the swamp shrinkage were evaluated based upon field investigations in 2011–2013 and analyses of remote sensing images and meteorological and hydrological data. Although a slight rise in the temperature was evident, there was no obvious decrease in the precipitation, indicating that climate change was not the primary cause of the recent swamp shrinkage. Remote sensing images indicated that roughly 920 km of artificial ditches excavated from the 1960s to 1990s have affected around 648 km 2 of swamp, accounting for 27% of the total shrinkage area (approximately 2400 km 2 ). Bed incision of the upper Yellow River was considered to be the primary cause for the long-term degradation of the Ruoergai Swamp. Ensuing headcut erosion of countless tributaries has induced drainage network extension, draining large areas of the swamp and lowering the groundwater levels. Headcut erosion and construction of the artificial channels have markedly increased the flow and sediment movement in this landscape.

Outburst floods from glacier-dammed lakes are major events associated with glacier thinning and volume reduction. This paper investigates jokulhlaups emanating from the glacier-dammed lake Ovre Messingmalmvatn at Rundvassbreen, an outlet glacier of the Blamannsisen ice cap in northern Norway. Since 2001, the lake has several times been observed to drain suddenly, causing jokulhlaup outbursts into the pro-glacial lake Rundvatnet. Varve analysis and lead-210 (210Pb) dating were used to date sediment cores taken from Rundvatnet. It was found that sedimentation from jokulhlaups is recognizable in the lake as distinct sand layers embedded in the varved silt-clay sequence which represents the normal lake sedimentation. Sand fractions were carried in suspension because of the extreme hydraulic conditions of jokulhlaups. The thickest sand layer was deposited during the 2001 jokulhlaup which lasted three days and had a total volume of 40 ×106 m3. Jokulhlaups were also recorded in 2005, 2007, 2009, and 2010; they each resulted in a sand layer. Annual sediment accumulation in Rundvatnet increased up to 10-fold during the years with jokulhlaup outburst floods, from a normal value of 1–2 mm yr−1 to 8–10 mm yr−1. Five other jokulhlaups were identified from the 1910–1930 sedimentation interval, in addition to those observed in 2001–2010; there appear to have been none for 70 years during 1931–2000. Each jokulhlaup was preceded by a period when the glacier thinned to a critical volume and could no longer withstand the hydrostatic pressure of Ovre Messingmalmvatn; consequently a tunnel developed beneath the glacier, leading to a jokulhlaup. Statistical analyses of the correlations between the pro-glacial sedimentation rate and temperature and precipitation suggested that although climate conditions are expected to influence sedimentation in the pro-glacial catchment, a host of other interacting factors moderate the availability and delivery of sediment to the pro-glacial system, making the processes responsible for changes in pro-glacial sedimentation to remain uncertain. Copyright © 2014 John Wiley & Sons, Ltd.

Alluvial reaches in the source region of the Yangtze and Yellow Rivers, located atop the Qinghai–Tibetan Plateau and mostly at elevations that are typically higher than 3500 m, have similar slope and valley setting conditions. However, alluvial reaches in the source region of the Yangtze River exhibit predominantly braided channel planforms, while equivalent reaches in the source region of the Yellow River have more diverse planform morphologies including anastomosing/braided, anabranching/braided, and anabranching/anastomosing reaches. The regional gradient of variation in riparian vegetation and interactions between vegetation development and hydrologic process are shown to be major factors influencing this difference in channel planforms. A short period above freezing, coincident with recurrent yet pulsed flows in the source region of the Yangtze River, suppress riparian vegetation growth, promoting the development of braided channel morphologies. In contrast, a milder climate, coincident with less variable flows in the source region of the Yellow River, permit the establishment of different forms of riparian vegetation, thereby supporting the development of a wider range of channel planform morphologies.

The development, stability, and growth direction of gravel mid-channel bars in rivers were studied by analyzing sediment distribution and vegetation development along the bars. Field studies and sediment sampling were conducted in the source region of the Yellow and Lancang rivers on the Qinghai Plateau. The results showed that the gravel bars in rivers always grow in the upstream direction, because gravel and sand are deposited at the upstream end of the bars. Gravel bedload stopped at the bar head. Sand and silt moved as suspended load during the flood season and were deposited at the bar tail due to vegetation resistance. Consequently, sediment size varied from gravel to sand and silt along the bars from the head to the tail on the bar surface. Dense vegetation coverage normally grew at the bar tail, while only pioneer species occurred at the bar head. The prevalent phenomena demonstrated the upstreamward growth of mid-channel bars.

Aquatic ecosystems of highland rivers are different from those of low altitude rivers because of the specific topography and environmental parameters associated with high altitudes. Yalutsangpo, the upper course of the Brahmaputra River, is the highest major river in the world, flowing from west to east across Tibet, China and pouring into India. Macroinvertebrates were sampled from Yalutsangpo and its tributaries, the Lhasa, Niyang, and Parlong Tsangpo Rivers, from October 2009 to June 2010, to study characters of the highland aquatic ecosystem. Altogether, 110 macroinvertebrate taxa belonging to 57 families and 102 genera were identified from the basin. The biodiversity and composition of macroinvertebrate assemblages were strongly affected by altitude gradients. Local diversity represented by taxa richness and the improved Shannon-Wiener index were high at altitudes of 3,300-3,700 m, among which suitability of habitat was higher due to the better integrated environmental conditions of water temperature, dissolved oxygen, and aquatic vegetation, etc. Macroinvertebrates were grouped into shredders, scrapers, predators, collector-filterers, and collector-gatherers according to their feeding behaviors. It was found that the distributions of the functional feeding groups varied with habitat altitudes. Shredders were present at altitudes of 2,900-4,400 m, while scrapers mainly inhabited altitudes of 3,500-4,500 m, and collector-filterers preferred 3,500-4,000 m. Even though the local taxa richness was not high at each site, the taxonomic composition and density of the assemblages varied greatly among the different sites, resulting in much higher regional diversity compared to the lowland river with similar flow and substrate conditions. The regional cumulative taxa richness of Yalutsangpo decreased and more families were lost as the altitude increased. However, some families that were newly present as the altitude increased were essential for sustaining the high regional biodiversity. The ordination diagram obtained from Detrended Correspondence Analysis indicated that altitude, river pattern, riverbed structures, bank structures, and flow conditions were the main factors that influenced the macroinvertebrate assemblages in the Yalutsangpo basin.

Quantitative measures of the relationships between channel morphology and the habitat use of Chinese sturgeon (Acipenser sinensis) can help management and regulatory agencies to quantify potential spawning habitats and develop recovery goals in view of the decreasing area of sturgeon spawning habitat. This study determined the specific bedform types at the pool–riffle scale and evaluated the slopes, aspects and bed load gradation composition of Chinese sturgeon spawning areas in the Yangtze River, China. A bedform differencing technique was used to objectively quantify the longitudinal riverbed profile into four distinct pool-riffle units that were independent of discharge. The vertical location of thalweg points within these units was quantified with a riffle proximity index. Chinese sturgeon spawning areas were mapped and correlated with the pool-riffle units, slopes and aspects. The results indicate that Chinese sturgeon spawning areas occur primarily in riffles. The majority of Chinese sturgeon spawning occurred at elevations greater than 75% of the difference in elevation between the nearest riffle crest and the pool bottom. The slope of spawning sites was distributed between 0.05 and 6.36, and the average aspects were 219.92 and 207.63, respectively. The bed load is mainly composted of gravel and pebble, sediment diameter concentrated on 50–500mm. These analyses of bedform morphology will assist regional fish managers in quantifying existing and potential Chinese sturgeon spawning habitats and will provide a quantitative framework for evaluating general ecological implications of channel morphology in the Yangtze River.

This study presents findings of the first systematic analysis of aquatic biotic assemblages in the source region of the Yellow and Yangtze Rivers. It provides an initial basis with which to select representative organisms as indicators to assess the aquatic ecological status of rivers in this region. Macroinvertebrates are considered to be good indicators of long-term environmental changes due to their restricted range and persistence over time. Field investigations of macroinvertebrates were conducted in August 2009 in the source region of the Yellow River, and in July 2010 in the source region of the Yangtze River. Altogether 68 taxa of macroinvertebrates belonging to 29 families and 59 genera were identified. Among them were 8 annelids, 5 mollusks, 54 arthropods and 1 other animal. In the source region of the Yellow River, taxa number, density and biomass of macroinvertebrates were 50, 329 individuals m−2 and 0.3966 g dry weight m−2, respectively. Equivalent figures for the source region of the Yangtze River were 29, 59 individuals m−2 and 0.0307 g dry weight m−2. The lower benthic animal resources in the source region of the Yangtze River are ascribed to higher altitude, higher sediment concentration and wetland degradation. Preliminary findings of this exploratory study indicate that hydroelectric power stations had a weak impact on benthic dwellers but wetland degradation caused by a series of human activities had a catastrophic impact on survival of macroinvertebrates. Ecological protection measures such as conservative grazing and vegetation management are required to minimize grassland degradation and desertification, and reduce soil erosion rate and river sediment discharge.

The 270 km long section of the Upper Yellow River at the First Great Bend is comprised of single channel and multiple channel systems that alternate among anastomosing, anabranching, meandering and braided reaches. The sequence of downstream pattern changes is characterized as: anastomosing-anabranching, anabranching-meandering, meandering-braided and braided-meandering. Remote sensing images, DEM data and field investigations are used to assess and interpret controls on these reach transitions. Channel slope and bed sediment size are key determinants of transitions in channel planform. Anastomosing reaches have a relatively high bed slope (0.86‰) and coarser sediment bed material (d 50 = 3.5 mm). In contrast, meandering reaches have a low slope (0.30‰) and fine sediment bed material (d 50 = 0.036 mm). The transition from a meandering to braided pattern is characterized by an increase in channel width-depth ratio, indicating the important role of bank strength (i.e. cohesive versus non-cohesive versus channel boundaries). Interestingly, the braided-meandering and meandering-braided transitions are coincident with variable flow inputs from tributary rivers (Baihe and Heihe rivers respectively). Theoretical analysis of the meandering-braided transition highlights the key control of channel width-depth ratio as a determinant of channel planform.

The spatial distribution of valley setting (laterally-unconfined, partly-confined, or confined) and fluvial morphology in the source region of the Yangtze and Yellow Rivers is contrasted and analyzed. The source region of the Yangtze River is divided into 3 broad sections (I, II and III) based on valley setting and channel gradient, with the upstream and downstream sections being characterized by confined (some reaches partly-confined) valleys, while the middle section is characterized with wide and shallow, laterally-unconfined valleys. Gorges are prominent in sections I and III, while braided channel patterns dominate section II. By contrast, the source region of the Yellow River is divided into 5 broad sections (sections I–V) based on valley characteristics and channel gradient. Sections I, II and IV are alluvial reaches with mainly laterally-unconfined (some short reaches partly-confined) valleys. Sections III and V are mainly confined or partly-confined. Greater morphological diversity is evident in the source region of the Yellow River relative to the upper Yangtze River. This includes braided, anabranching, anastomosing, meandering and straight alluvial patterns, with gorges in confined reaches. The macro-relief (elevation, gradient, aspect, valley alignment and confinement) of the region, linked directly to tectonic movement of the Qinghai-Tibet Plateau, tied to climatic, hydrologic and biotic considerations, are primary controls upon the patterns of river diversity in the region.

This paper reviews the state-of-the-art eco-hydraulic and eco-sedimentation studies in China, particularly focusing on the impact of hydropeaking, habitat suitability modelling, bio-invasion control strategies, sediment transport effects on river ecology, and ecological restoration. Field investigations found that macro-invertebrate species number reduced nearly to zero in a short reach downstream of a dam due to hydropeaking, resulting from a hydropower station. Habitat suitability modelling for the Chinese sturgeon indicated that the habitat suitability was reduced after the Three Gorges Dam began filling. Macro-invertebrate species number and fishery harvest reduced sharply after riparian lakes were cut-off from the Yangtze River. Invasion and dense attachment of mussels on water transfer tunnel walls have caused biofouling in many countries. An effective control strategy, using hydraulic control methods for the golden mussel invasion is proposed. Erosion, sediment transportation, and deposition create...

Golden mussel Limnoperna fortunei(Dunker 1857) is a filter-collector species of fresh water mussel originating from southern China. In the water transfer tunnels from the East River to Shenzhen and Hong Kong, golden mussels attach to the walls of pipelines and gates, causing serious biofouling, increased flow resistance, and resulted in corrosion of the tunnel wall. Golden mussel has very high environmental adaptability and may colonize habitats with low dissolved oxygen and a wide range of trophic levels. The colonization process of the species on solid surface was studied in the Xizhijiang River, a tributary of the East River and the main water resource of Shenzhen from March 2010 to April 2011. The results showed that the golden mussel completed three generations and reproduced six cohorts per year in the tropic zone. Water temperature was the controlling factor for the growth rate and maturity of each cohort. Based on the results, an ecological method for controlling the invasion of golden mussels in water transfer tunnels was proposed.

The Cesium-137 technique was used to estimate soil erosion in the Xihanshui River Basin. More than 100 samples were taken from 10 sites and 20 hillslopes with a 10cm diameter hand-operated core driller. Each sample was 60 cm long. The 137 Cs activity was analyzed by gamma spectrometry. The simplified mass balance model and the profile distribution model were used to calculate soil erosion and deposition rate. The local 137 Cs reference ranged from 1,600 to 2,402 Bq m −2 . The data shows an exponential decrease of mass concentration and amount with depth in an undisturbed soil profile. Soil erosion in the river basin is moderate or severe on cultivated land with annual erosion rates of 2,000–6,000 t km −2 yr −1 . In general, very severe or severe soil erosion occurred at the upper slope sections, moderate or severe soil erosion at the middle section, and moderate or slight soil erosion at the lower slope sections. On the slopes with natural vegetation, consisting of herbaceous and wood species, the erosion rate is much lower or not detectable. On the lower section of slopes with well-developed vegetation however, there was no soil loss, instead deposition occurred at a rate of more than 300 t km −2 yr −1 . The slope gradient and vegetation cover affected soil erosion and deposition rates. In general, the rate of soil erosion was proportional to the slope gradient and inversely proportional to the degree of vegetative cover.

Field investigations of macroinvertebrates in three Chinese rivers were conducted twice in 2009. Altogether 88 taxa were identified. Annelids, arthropods and mollusks were the dominant taxonomic group in the Songhua River, the Yongding River and the West River, respectively. Collector-gatherers were the most abundant group in the relatively lentic river sites, where the bottom was largely organic-rich silt. Epilithic collector-filterers and scrapers were dominant in the lotic river sites, where the bottom was mainly dominated by stone substrate. Based on statistical analyses, water physico-chemical variables (total phosphorus and conductivity) played a key role in structuring macroinvertebrate assemblages in silt substrate, while hydrological variables (median grain size of substrate and water velocity) mainly affected macroinvertebrate assemblages in stone substrate. In silt substrate, density and biomass of collector-gatherers increased with increasing total phosphorus. In stone substrate, total density peaked in the cobbles, while total biomass peaked in the bedrock.

The influence of vegetation upon bedload transport and channel morphodynamics is examined along a channel stability gradient ranging from meandering to anabranching to anabranching–braided to fully braided planform conditions along trunk and tributary reaches of the Upper Yellow River in western China. Although the regional geology and climate are relatively consistent across the study area, there is a distinct gradient in the presence and abundance of riparian vegetation for these reaches atop the Qinghai–Tibet Plateau (elevations in the study area range from 2800 to 3400 m a.s.l.). To date, the influence of vegetative impacts upon channel planform and bedload transport capacity of alluvial reaches of the Upper Yellow River remains unclear because of a lack of hydrological and field data. In this region, the types and pattern of riparian vegetation vary with planform type as follows: trees exert the strongest influence in the anabranching reach, the meandering reach flows through meadow vegetation, the anabranching–braided reach has a grass, herb, and sparse shrub cover, and the braided reach has no riparian vegetation. A non-linear relation between vegetative cover on the valley floor and bedload transport capacity is evident, wherein bedload transport capacity is the highest for the anabranching reach, roughly followed by the anabranching–braided, braided, and meandering reaches. The relationship between the bedload transport capacity of a reach and sediment supply from upstream exerts a significant influence upon channel stability. Bedload transport capacity during the flood season (June–September) in the braided reach is much less than the rate of sediment supply, inducing bed aggradation and dynamic channel adjustments. Rates of channel adjustment are less pronounced for the anabranching–braided and anabranching reaches, while the meandering reach is relatively stable (i.e., this is a passive meandering reach).

Diverse wetlands such as alpine meadows, lakes and peatlands are extremely important resources for water supply and ecological protection of aquatic ecosystems in the source zone of the Yellow River. Field surveys (2010–2014) and interpretations of remote sensing images are used to provide insights into the distribution of wetlands in this region and associated notions of landscape connectivity. Ruoergai Swamp (Zoige) at the eastern margin of the Qinghai–Tibet Plateau in the Yellow River Source Zone is the world’s largest plateau peat wetland. A case study of this swamp shows that it has shrunk greatly since the 1950s. Environmental suffering (i.e. desertification, grassland degradation and run-off reduction) is leading to the ecological degradation of the Ruoergai peatlands, severely affecting local herdsmen and the surrounding communities (e.g. Sichuan Basin and the Upper Yellow River). Wetland degradation is affected by both global climate warming and human activities (especially construction of artificial ditches). The second half of this chapter uses field and laboratory analyses of benthic macroinvertebrates as indicators to assess the status of aquatic ecosystems in the region, contrasting findings from the Upper Yellow and Yangtze rivers. Human activities such as artificial ditch system, overstocking and peat mining have impacted upon local aquatic ecosystems. Such pressures have been accentuated by the economic and social development since the 1980s.

Deltas are the most dynamic part of large rivers and the characteristics of deltas reflect the basic nature of morphodynamics, ecology and anthropogenic influence. The authors investigated many deltas of large rivers, including the Yellow, Yangtze, Pearl, Rhine, Nile, Mississippi, Luanhe and Ebro rivers. Data were collected and sediment, water, benthic invertebrates and fish were sampled. Statistical analysis showed that deltas can be classified into male deltas and female deltas. The deltas of the Yellow, Mississippi, Luanhe, Ural and Ebro rivers are male deltas. Male deltas extend into the ocean, each with only one or two channels, forming a fan-shape. Its development process is accompanied with periodic nodal or random avulsions. Male deltas develop if the sediment load/water ratio is high and the tidal range is low. The deltas of the Yangtze, Rhein-Meuse-Scheldt, Pearl and Irrawaddy rivers are female. Female deltas consist of complex channel networks and numerous bars and islands. Female deltas develop if the load/water ratio is not high and tidal current is relatively strong. Female deltas provide stable and multiple habitats for various bio-communities. Therefore, the biodiversity of female deltas and the taxa richness of benthic invertebrates and fish are much higher than that of male deltas. Human activities reduced sediment load and change the delta gender from male to female. Male rivers have high levees in their lower reaches and estuary. Several rivers originate from the levees of a male river and flow parallel with the river into the sea. Appearance, persistence, length and stability of these rivers depend on the male river to which they are attached. Therefore, these rivers are named parasitizing rivers. In general, parasitizing rivers have no tributaries and almost no drainage area. The runoff of these rivers comes from the rainfall on the surrounding area, and therefore, the flow discharge exhibits very sharp peaks during rainfall. The Yellow and Luanhe rivers have many parasitizing rivers. Some of the parasitizing rivers are quite long, with a length of 400-500 km, such as the Tuhai River and Majia River. Management of parasitizing rivers must be integrated into management strategies of their father rivers.

Rehabilitation of Shengou Creek, a small, steep mountain stream in southwestern China that is prone to debris flows, started more than 30. years ago through an integrated program of engineering applications (check dams and guiding dikes), biological measures (reforestation), and social measures (reducing human disturbance). Small and medium-sized check dams and guiding dikes were constructed on key upper and middle sections of the creek to stabilize hillslopes and channel bed. Meanwhile, Leucaena leucocephala, a drought-tolerant, fast-growing, and highly adaptive plant species, was introduced to promote vegetation recovery in the watershed. The collective community structure of tree, shrub, and herb assemblages in the artificial L. leucocephala forest, which developed after 7. years, enhanced soil structure and drastically reduced soil erosion on hillslopes. Cultivation of steep land was strictly controlled in the basin, and some inhabitants were encouraged to move from upstream areas to downstream towns to reduce disturbance. These integrated measures reduced sediment supply from both hillslopes and upstream channels, preventing sediment-related hazards. The development of natural streambed resistance structures (mainly step-pool systems) and luxuriant riparian vegetation aided channel stability, diversity of stream habitat, and ecological maintenance in the creek. These findings are compared with Jiangjia and Xiaobaini Ravines, two adjacent non-rehabilitated debris-flow streams which have climate and geomorphologic conditions similar to Shengou Creek. Habitat diversity indices, taxa richness, biodiversity, and bio-community indices are much higher in Shengou Creek relative to Jiangjia and Xiaobaini Ravines, attesting to the effectiveness of rehabilitation measures. 2011 Elsevier B.V.

Flood has kept causing disasters to the east river basin. This paper developed an inundation risk model to estimate the economic loss in the scenarios of events with different frequency. A method was used to estimate the flooding area in the east river basin, using the digital elevation model (DEM), GIS spatial analysis, and hydrology calculation. Since the flow in East River is partly controlled by several reservoirs, the flooding area has been greatly reduced. The model was also used to estimate the flooding area in the case of reservoir control. Results indicated that there is a logarithm correlation between the flooding area and the flood frequency. The decrease in flooding area due to reserviors will be about 25%. Some sediment problems that alter the fluvial process like sediment mining were also discussed with this model.

The Wenchuan Earthquake caused a large number of avalanches and landslides at different scales. It is extremely significant to evaluate the sediment in the earthquake river basins. Along the 38 km long upper Mianyuan River 196 landslides and avalanches happened during the earthquake, which have formed 25 landslide dams and quake lakes. The total volume of sediment erosion due to earthquake was about 115 million m3, which is 75 times higher than the soil erosion in normal years. Only a part of the solid material could be transported by the river water flow as suspended load and bed load. The total volume of bed load deposit in the river and the quake lakes was 1.43 million m3. Moreover the quake lakes had also trapped 0.12 million m3 suspended load. Only 0.18 million m3 of fine sediment had been drifted through the quake lakes and transported into the lower reaches of the Mianyuan River. The wide range of size distributions of sediment from earthquake erosion caused the extreme difference in the amounts of sediment erosion and transportation. Most of the sediment from earthquake erosion can be only transported for a short distance by landslides and debris flows. Less than 0.2% of the total volume of sediment from earthquake erosion may be transported into large rivers. Therefore, earthquake erosion has little effect on the sediment transportation and fluvial processes in the large rivers.

Benthic macro-invertebrates are vital components of river ecosystems. The effects of fluvial processes and human activities on the distribution of macro-invertebrates were studied through field investigations and experiment. Sixty-one sampling sites on 31 rivers in China were selected to investigate the structures of macro-invertebrate assemblages. The rivers, according to their fluvial conditions, are classified as streams with a stable channel bed, degrading channel bed, aggrading channel bed, and intensive bed load motion. The structures of macro-invertebrate fauna for the four types of rivers are very different. Stable rivers have a large number of individuals, abundant fauna, and high biodiversity; while the density and taxa richness for degrading rivers are small, and those for aggrading rivers are much less; whereas the ecology of rivers with intensive bed load motion are the worst. This paper proposes that streambed stability is the primary influential factor shaping the structure of benthic macro-invertebrate communities. Organic pollution can obviously result in the decrease of biodiversity, in the simplification of macro-invertebrate structures, and in the distortion of functional feeding group composition. In a river with high total nitrogen content, the relative abundance of collector-gatherers is high, and that of collector-filterers, scrapers, shredders, and predators are low. Scrapers, shredders, and predators disappear in severely polluted rivers. The isolation of aquatic habitat results in a distinct decrease of individual numbers and taxa richness. This result demonstrates that the connectivity of aquatic habitat significantly affects macro-invertebrate assemblages. A practical method to calculate a Habitat Suitability Index (HSI) is proposed, integrating the effects of the primary physical (including biotic and abiotic) and chemical factors. The biodiversity and taxa richness increase non-linearly with HSI.

Alluvial floodplains contain four types of abandoned channels: old river courses, oxbow lakes, oxtail lakes and riparian wetlands. These result from avulsions, meander cutoffs, ice-jam floods and stem-channel shifts, respectively. With the exception of old river courses, which belong to terrestrial ecosystems, abandoned-channel types are important components of freshwater ecosystems. During 2006–2009, we conducted systematic investigations of macroinvertebrates in three types of freshwater abandoned channels and identified 93 taxa of macroinvertebrates belonging to 51 families and 88 genera. In the assemblage composition, most taxa were similar to those found in river-isolated lakes and river mainstreams. Moreover, abandoned channels supported many unique benthic taxa, which are important complementary resources for the entire river system. In the abandoned channels that were covered with a layer of silt, standing crops were higher than that found in the river mainstream where the bed sediment consisted mainly of sand. Conversely, in abandoned channels that were covered with fine sand, standing crops were lower than in the gravel streambed. Some abandoned channels, such as the riparian wetlands of the East River that are freely connected with the mainstream, were characterized by the highest biodiversity and the greatest biomass. In regions less affected by human activities, abandoned channels need to be connected with mainstreams by flooding at least once every 3 years to maintain at least half of the maximum amount of macroinvertebrate resources. In regions more affected by human activities, abandoned channels need to be connected with mainstreams at least once every year. Copyright © 2011 John Wiley & Sons, Ltd.

The newly bared rocks created by the Wenchuan earthquake are undergoing continual intensive erosion in the form of detachment and movement of individual grains. Grain erosion is defined as the phenomenon of breaking down bare rocks under the action of insolation and temperature change, detachment of grains from the rockwalls by wind, flow down of grains on the slope under the action of gravity, and accumulation of grains at the toe of the mountain, forming a deposit fan. The Wenchuan earthquake, which occurred in Sichuan on May 12, 2008, caused thousands of avalanches and landslides and left scars on slopes and a huge area of bare rocks. Grain erosion causes flying stones, injured humans and resulted in numerous slope debris flows. The process of grain erosion and strategies to limit the erosion were studied by field investigations and field experiments. According to these field investigations and field studies, the most serious grain erosion occurs in spring and early summer when it is very dry. Rocks are broken down to grains under the action of insolation and temperature change. Then, wind blows the grains from the bare rock down slope. Experimental results showed that the amount of grains blown down by wind per area of rock surface per unit time is proportional to the fourth power of the wind speed. However, the size of the grains blown down by wind increases linearly with the wind speed. An experiment proved that grain erosion can be controlled with two moss species. Moss spores were mixed with clay suspension and splashed on bare rocks. The moss species germinated on the rock surface in one month and greened the bare rocks in two months. The moss layer protected the rocks from insolation and mitigated the effects of temperature change, thus effectively mitigated grain erosion.

The Wenchuan earthquake caused numerous landslides and avalanches, which initiated causal chains of geological and ecological disasters. Field investigations and field experiments were performed in the earthquake area in 2008 and 2009 to study the disaster chains. Four types of disaster chains have been identified and seven cases have been studied. In the disaster chains, each episode was caused by the previous episode, or the causal episode. In the first chain, landslide created a quake lake, which was followed by landslide dam failure flood and very intensive fluvial process. The last episode of the chain was loss of habitats and destruction of aquatic biocommunities. The Tangjiashan and Huoshigou landslides initiated such a type of disaster chain. The second chain consisted of landslide, drainage system burying, debris flows, and development of new drainage system and intensive fluvial process. The Wenjiagou landslide initiated such a type of disaster chain. The third chain consisted of avalanches, grain erosion (unusual erosion of bare rocks due to insolation and temperature change), slope debris flows, and flying stones. Many such disaster chain events occurred on the mountains by the Minjiang River section from Yingxiu to Wenchuan. The fourth chain has only two episodes: avalanches during the earthquake occurring on elevation between 100 and 800 m from the riverbed, and rock falls or new avalanches due to increased slope angle of high mountains (400–1,500 m from the riverbed). The Chediguan bridge was broken by such avalanches in July 2009, in which six were killed and more than 20 were injured. For all the disaster chains, the volume of mass movement in each episode was much less than the causal episode (previous episode). In other words, there was an attenuation along the causal chains. The attenuation factor is defined as the ratio of the volume of mass movement or affected area in one episode of a chain to the volume or affected area in the causal episode. The study concluded that the attenuation factor ranges from 0.02 to 0.3. Macroinvertebrates were used as indicator species to evaluate the ecological effect of the disaster chains. The number of species was greatly reduced by the causal chains, although the river section was not directly affected by landslides.

A field experiment using an artificial step-pool system was conducted to restore the Diaoga River, a seriously incised mountain stream in Yunnan-Guizhou Plateau, southwest China. Twenty-four artificial steps, designed to mimic natural step forms, were constructed on three stretches of about 260 m length in the middle reach of the river. Channel topography, hydraulic features, aquatic habitats and stream ecology were monitored for 20 months. Following the construction of the artificial step-pool system, the stream bed development coefficient increased significantly. This indicates that actions helped to dissipate flow energy more effectively, enhancing the stability of the stream bed. The step-pools have effectively controlled the incision and stabilized the river morphology. In addition, they have created multiple habitats for different species and increased the habitat diversity. Improvement of the aquatic ecosystem is confirmed by increased density and taxa richness of benthic macro-invertebrates, which...

The beautiful Longmenshan area is one of the main tourist attractions in Sichuan Province, China. The epicenter of a catastrophic earthquake measured at 8.0 Ms (China Seismological Bureau), occurred within this area at Wenchuan (31 degrees 01'16"N, 103 degrees 22'01"E) at 14:28 May 12, 2008 (Beijing time). The earthquake triggered numerous types of landslide transport and hazards, including soil and debris avalanches, rockfalls, slumps, debris flows, creation of barrier lakes and slope fattenings. This paper examines the landslide hazards in the Longmenshan area caused by the earthquake using remotely sensed images, mainly Beijing-1 Microsatellite data before and after the earthquake, compared to digital elevation maps and slope gradient maps, land use and vegetation cover maps. Areas of erosion and loss of vegetation were compared from pre- and post-earthquake data, from which were calculated changes in vegetated areas, bare slopes, and mass movement during the earthquake. These events occurred over altitudes from 1000 to 4000 m and on slope angles between 25 and 55 degrees. The results show that the total area of erosion and land movement due to the earthquake increased by 86.3 km(2) (19.2% of the study area). Compared with pre-earthquake, the areas of very low intensity soil erosion and moderate intensity soil erosion were respectively reduced by 3.6 km(2), 24.3 km(2) and 30.9 km(2). On the other hand, the areas of severe and very severe intensity soil erosion were substantially increased by 45.8 km(2) and 99.2 km(2). In the post-earthquake stage, the bare areas (vegetation cover

Stream networks and knickpoints in the Sanjiangyuan RegionThe source area of the Lancang (Mekong), Yangtze and Yellow rivers is named in Chinese Sanjiangyuan (source of three rivers). Geographical characteristics of these rivers, and various rivers at the margin of the Qinghai-Tibetan Plateau (Jialing, Minjiang, Dadu, Yalong and Jinsha) are summarized from field investigations along with digital elevation model (DEM) analyses and satellite images. Uplift of the Qinghai-Tibetan Plateau has resulted in an asymmetrical distribution of tributaries for stream networks at the margins of the plateau. Almost all tributaries join the trunk stream from the northwest. Three types of drainage network are evident: plume, nervation and dendritic. In general, plume networks have a large number of first order streams. Nervation networks have a main stream and parallel tributaries. Dentritic networks are characrterized by continuous bifurcation and have a branch-like appearance. Most stream networks in the Sanjiangyuan region are of the nervation type. Several large knickpoints are evident along the longitudinal profiles of the Yellow and Yangtze Rivers. Channel aggradation immediately upstream of these knickpoints marks a transition in river processes from vertical bed evolution (i.e. incision) to horizontal channel adjustment (and associated braided and anabranching channels).

The formation and geomorphic evolution of the Jiuduansha Shoal are investigated over the past 50 years in this paper. The sedimentary processes, formation, and geomorphic evolution of the Jiuduansha Shoal in the Yangtze River Estuary, eastern China, are analyzed based on digitized sea maps from 1945 to 2001, satellite images from 1975 to 2001, and field survey data in the spring-neap tidal cycle in the dry and flood seasons in 2003. The suspended sediment concentration and hydrodynamics of the North Passage and South Passage during the dry and flood seasons in the spring-neap tidal cycle in 2003 were investigated, and relations between the North Passage and South Passage of the Jiuduansha Shoal are analyzed. Results show that seasonal and spring-neap tidal cycle variations in sediment and water discharge from the drainage basin correspond to erosion and deposition on the Jiuduansha Shoal. The results and data can provide useful information for the management of the Yangtze River Estuary and restoration of the estuarine tidal flat ecology.