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Impact of water diversion on the morphological development of the Lower Yellow River
Abstract
In this paper we carry out a theoretical analysis based on the general one-dimensional morphodynamic model for rivers in order to show how the morphological equilibrium of a river is influenced by water and sediment diversion/supply along the river. The results of the analysis show that large scale water diversions, like those along the Lower Yellow River, can cause the development of a convex riverbed profile in the long-term. Deposition will take place along the whole reach of the river, with an increasing deposition depth from downstream to upstream. The slope of the river bed increases from upstream to downstream. Furthermore, an analysis on the morphological time scale shows that this development in the Lower Yellow River will take a time period on the order of decades to centuries. The results of the analysis have been compared with observations in the Lower Yellow River. Since the second half of the 1980's large scale water diversions from the Yellow River have been taking place. The observations show that this has indeed led to significant sedimentation along the river.
... The convex longitudinal bed profile is also theoretically predicted by Wang et al. (2008) when incorporating the continuous water diversion effects in the governing equations (including the mass and momentum conservations for flow and mass conservation for sediment load) for the equilibrium state (derivatives in time become zero). When employing a spatially varying channel width, Wang et al. (2008) pointed out that the longitudinal shape should be related to the variation of the specific discharge along the river, rather than the total discharge as suggested by Wang and Hu (2004). ...
... The convex longitudinal bed profile is also theoretically predicted by Wang et al. (2008) when incorporating the continuous water diversion effects in the governing equations (including the mass and momentum conservations for flow and mass conservation for sediment load) for the equilibrium state (derivatives in time become zero). When employing a spatially varying channel width, Wang et al. (2008) pointed out that the longitudinal shape should be related to the variation of the specific discharge along the river, rather than the total discharge as suggested by Wang and Hu (2004). However, in their application to the LYR, the variation of the specific discharge along the river is simplified to be only affected by continuous water diversions. ...
... This may be inappropriate as the water diversion effect could also be strengthened or weakened by the longitudinal change of channel width through the specific discharge. Furthermore, Wang et al. (2008) consider only the idealized scenario of continuous water diversions along the river, whereas in reality, water diversions are discrete. It is unclear how significantly these simplifications have influenced the analysis. ...
Abstract: Water diversions along alluvial rivers cause water and sediment loss, and thereby affect morphological development. Assuming spatially continuous diversions along a constant-width channel, previous studies suggest a longitudinally convex bed at the equilibrium state. However, the validity of a convex bed profile for practically discrete diversions in natural channels of longitudinally varying width remains to be justified. Moreover, such equilibrium analysis does not reveal the morphological time scale (MTS) associated with water diversions. To solve these issues, a general theoretical framework is proposed for predicting the equilibrium state of the fluvial system, which is applicable to both continuous and discrete water diversions in a longitudinally width-varying channel. Numerical experiments complement the MTS studies for water diversions. The effects of diversion intensity, diversion placement (discrete and continuous), and diversion scheme (pure water and water-sediment mixture) are also systematically studied. The present work confirms the previous findings that water diversions lead to a decrease of the equilibrium depth with respect to natural conditions and a convex bed in a constant-width channel. Moreover, it reveals that in a widening channel a convex bed also develops under water diversions, whereas convex, concave, or quasi-linear beds may occur in a narrowing channel. Nonmonotonic beds may develop in a strongly narrowing channel, depending on the diversion schemes. On large spatial scales, diversion placement is less important for the equilibrium development. The MTS for water diversions and natural development are very similar and large, indicating considerable influences of water diversions on river morphology. The present work advances the understanding of the long-term effect of water diversions on river evolution.
... where =(dL/dt)/L (s -1 ) is the progradation rate of the river mouth normalized by L, t (s) is time, and ie=tan is the equilibrium bed slope (see Wang et al. (2008) for a detailed derivation). ...
... As a result, the lower reach of the Yellow River approaches the equilibrium profile with a relatively low and relatively high FP and SP (the stars in Figure 3). Nevertheless, the longitudinal profile of the lower Yellow River would be a convex form due to water diversion, if not for river mouth progradation that plays the counteracting role to create the actual concave profile (Wang et al., 2008). In contrast, in the physical experiment conducted by Bijkerk et al. (2016), the relatively high equilibrium bed slope (0.01) and high progradation rate (0.25 m/h) result in a high A/S ratio (see Eq. (4)). ...
Plain Language Summary
As a key feature of a river, the bed level along the river, i.e., the river longitudinal profile, affects flooding, navigation, etc., and thus greatly influences human societies and natural ecosystems. However, the effects of the seaward progradation of a river mouth on the evolution of the river longitudinal profile are still unclear. Given the increasing influence of human activities and climate change on this critical downstream control, understanding these effects becomes imperative. A new theoretical framework incorporating the effects of river mouth progradation on the evolution of a river longitudinal profile is developed and tested by numerical experiments, field observations, and numerical and laboratory data from the literature. The results show that the seaward progradation of a river mouth could potentially lead to the formation of a concave river longitudinal profile. Specifically, we found that there exists a critical condition in which the sediment supply is insufficient to balance the seaward progradation of the river mouth, causing the typical concave upward longitudinal profile to form. The proposed theoretical framework further suggests that sea level rise tends to increase the concavity of the longitudinal profile for river with a relatively low equilibrium bed slope and progradation rate.
... To supply water and electricity, 11 major reservoirs have been constructed in the mid and upper reaches of the basin since the 1970's (Sun et al., 2008). This has resulted in a substantial reduction in sediment loads (and flow), now estimated to be approximately 1/10 of natural (Wang et al., 2008). This alteration to the natural sediment-water balance is considered the primary cause of ecosystem degradation in the lower Yellow River (Li, 2005;Li et al., 2007). ...
... The most significant flow alteration included an increase in the frequency and duration of cease to flow days and the extent (river length) of zero-flow conditions (maximum recorded river length 687 km extending upstream from the river mouth) (Sun et al., 2008). Sediment loads were also reduced to one-tenth of natural which resulted in substantial changes to substrate composition in sedimentary environments of the delta (Wang et al., 2008). In downstream riverine reaches, changes to the sediment-water balance led to substantial sedimentation which reduced channel cross-sectional area, the magnitude of bank-full flows and flood discharge capacity, and increased water stage heights (Ru et al., 2003). ...
Extensive agricultural, industrial and urban development in the Yellow River, China, have modified the sediment-water balance, flow and inundation regimes, longitudinal connectivity, integrity of riparian vegetation, and water quality. Macroinvertebrate assemblages in the bed sediment of main channel and major reservoirs of the Yellow River are described in detail for the first time. A total of 74 taxa comprising 17 taxa of oligochaetes, 48 taxa of aquatic insects, 5 taxa of molluscs, and 4 taxa of other animals were recorded. A range of feeding guilds were represented, including, collector-gatherers (32 taxa), predators (17 taxa), scrapers (16 taxa), shredders (6 taxa) and collector-filterers (2 taxa). Both the mean density and biomass of macroinvertebrates were significantly higher in sites located in the artificial reservoirs compared with the main river channel. Assemblages varied spatially; Oligochaetes dominated assemblages in upper reaches, insects dominated in middle reaches and other animals (e.g. Crustacea) dominated in lower reaches. Collector-gatherers were dominant throughout the entire river. Classification analysis identified five site-groups on the basis of macroinvertebrate presence/absence: downstream of reservoirs; vegetated sites; reservoir sites; polluted sites, and; lower-reach sites. Lower macroinvertebrate richness, density and biomass, compared with other similar large rivers, were attributed to modification of the sediment-water balance and associated disturbance of benthic habitats. Pollution, stability of sediment and sediment concentration combined to influence the distribution of macroinvertebrates. This knowledge will substantially benefit the recent focus on the health and environmental water requirements of the Yellow River.
... In single-thread fluvial channels, their morphological evolution under disturbances has received extensive attention (Best, 2019;Wohl et al., 2015). With fixed channel width, the evolution of longitudinal profile of river channel under human interventions or natural changes has become the main focus (Blom, Arkesteijn, et al., 2017;Gao, Nienhuis, et al., 2020;Wang et al., 2008;Ylla Arbós et al., 2023;Zheng et al., 2022). This is basically built upon the in-depth understanding of the equilibrium longitudinal profiles of river channels thus far (Blom et al., 2016;Chang, 1986;Ferrer-Boix et al., 2016;Gao, Li, et al., 2020). ...
Deltaic channel networks are important conduits for water and material supplies to the fluvial and coastal communities. However, increasing human interventions in river deltas have altered the topology and geometry of channel networks as well as their long‐term evolution. While the morphological evolution of a single channel has received extensive studies, the system‐wide morphological responses of channel networks to local disturbances remain largely unclear. Here we investigate the morphological responses of a bifurcating channel network subject to local disturbance of channel deepening due to dredging and sand mining through idealized simulations, and further compare the results with the reference scenarios of a single channel and theoretical analysis of the phase plane. The results show that the infilling of the local deepening is associated with the erosion of the entire branch, which also causes system‐wide effects on the siltation of the other branch. The morphological responses of the bifurcating channel network consist of a relatively short stage for the infilling of the local deepening followed by a relatively long stage for recovering the equilibrium configuration of the river bifurcation. The system‐wide effects of the local disturbance arise from the altered water surface slope and water partitioning downstream of the bifurcation due to the local deepening. Also, the prolonged recovery of the equilibrium configuration is consistent with theoretical analysis, which reveals a slow evolution of the bifurcation when approaching the equilibrium. Our results can help understand the long‐term morphological responses of large‐scale complex channel networks and inform water managements under increasing human interventions.
... During 1978-2017, sea level rose notably in the bay at around 4.6 mm/a, which resulted in increased flood risk areas and the increased frequency and severity of storm surges (Feng et al., 2018). The salt marsh in the southern Hangzhou Bay is an important sink for sediment from the Changjiang (Yangtze) River and Qiantang River (Li and Xie, 1993;Che et al., 2003;van der Wegen and Roelvink, 2008;Wang et al., 2008) and will most probably be affected by human activities surrounding the bay and by sea level rise. Previous studies conducted in the Andong salt marsh focused on identifying the heavy metal pollution (Pang et al., 2015) and biogeochemistry of sedimentary organic matter along the surface sediments across transects of the salt marsh (Yuan et al., 2017). ...
Salt marshes are important carbon and nutrient sinks that are threatened by climate changes and human activities. In this study, the accumulation rates of sedimentary total organic carbon (TOC), total nitrogen (TN), and total phosphorus (TP) from two cores in the Andong salt marsh, Hangzhou Bay, were investigated to determine whether TOC, TN, and TP show increasing or decreasing trends toward the present. The TOC accumulation rates at the relatively lower marsh were lower during 1990–1996 (1.63–2.37 g/(cm2·a)) than 1997–2014 (1.15–4.30 g/(cm2·a)). The TN accumulation rates increased from 1990 (0.14 g/(cm2·a)) toward 2012 (0.40 g/(cm2·a)), then decreased toward 2014 (0.16 g/(cm2·a)). The TP accumulation rates were lower during 1990–1999 (0.10–0.21 mg/(cm2·a)), and decreased from 2000 (0.32 mg/(cm2·a)) toward 2014 (0.15 mg/(cm2·a)). The TOC accumulation rates along the relatively upper marsh during 1982–1992 (1.18–3.25 g/(cm2·a)) were lower than during 1998–2010 (2.30–4.20 g/(cm2·a)), and then decreased toward 2015 (2.15 g/(cm2·a)). TN increased from 1982 (0.18 g/(cm2·a)) to 2005 (0.41 g/(cm2·a)), then decreased toward 2015 (0.22 g/(cm2·a)). TP accumulation rates fluctuated within a narrow range during 1982–1997 (0.21–0.41 mg/(cm2·a)), increased from 1998 (0.50 mg/(cm2·a)) to 2004 (0.87 mg/(cm2·a)), then decreased to 2015 (0.38 mg/(cm2·a)). Thus, increases in accumulation rates of TOC, TN, and TP from the 1980s to 1990s indicates that the marsh likely served as carbon and nutrient sinks, then the rates decreased during 2000–2015 due probably to the reduced sediment inputs from rivers and intensified sea level rise.
... This is in contrast to the study of Ratliff et al. (2018) who simulated multiple avulsion cycles. Notably, the backwater length is estimated as (Paola & Mohrig, 1996), where h e and i e are the equilibrium water depth and slope of the river channel in this study which can be derived from Equations 9 and 10 following Wang et al. (2008). ...
It is widely recognized that waves inhibit river mouth progradation and reduce the avulsion timescale of deltaic channels. Nevertheless, those effects may not apply to downdrift‐deflected channels. In this study, we developed a coupled model to explore the effects of wave climate asymmetry and alongshore sediment bypassing on shoreline‐channel morphodynamics. The shoreline position and channel trajectory are simulated using a “shoreline” module which drives the evolution of the river profile in a “channel” module by updating the position of river mouth boundary, whereas the channel module provides the sediment load to river mouth for the “shoreline” module. The numerical results show that regional alongshore sediment transport driven by an asymmetric wave climate can enhance the progradation of deltaic channels if sediment bypassing of the river mouth is limited, which is different from the common assumption that waves inhibit delta progradation. As such, waves can have a trade‐off effect on river mouth progradation that can further influence riverbed aggradation and channel avulsion. This trade‐off effect of waves is dictated by the net alongshore sediment transport, sediment bypassing at the river mouth, and wave diffusivity. Based on the numerical results, we further propose a dimensionless parameter that includes fluvial and alongshore sediment supply relative to wave diffusivity to predict the progradation and aggradation rates and avulsion timescale of deltaic channels. The improved understanding of progradation, aggradation, and avulsion timescale of deltaic channels has important implications for engineering and predicting deltaic wetland creation, particularly under changing water and sediment input to deltaic systems.
... Therefore, the sediments at the Andong tidal flat are influenced by both the Qiantang River and the Yangtze River, as well as the tidal current from the East China Sea. The Andong tidal flat is an accretion flat (Wang et al. 2008;Wegen and Roelvink 2008) with a tidal range of 2-8 m and wave amplitude of 1-2.5 m s ¡1 . In addition, this 300-km 2 tidal flat can be divided into a high, a middle, and a low tidal flat from onshore to offshore ( Figure 1B). ...
In this study, we collected two sediment cores (C1 and C2) from the Andong tidal flat, Hangzhou Bay, and studied the temporal variations of heavy metals in the cores. Vertical distributions of heavy metals were almost unchanged in both cores before 2000. After 2000, however, the heavy metal concentrations increased dramatically, suggesting that the sediments have been affected by enhanced human pollution in the recent decade. In the core C1, the sediments were severely polluted by Pb, moderately to considerably polluted by Cr and Zn, and low to moderately polluted by other heavy metals. The core C2 was relatively unpolluted before 2000 and low to moderately polluted after 2000. Multi-statistical analyses indicated that the core C1 was additionally contaminated by local human activities such as wastewater discharge and the Hangzhou Bay Bridge. The heavy metals in the core C2, however, were largely contributed by the Yangtze River and controlled by sedimentation process. The calculated sedimentary flux (4 - 8 g m⁻² a⁻¹) of heavy metals generally increased with time. It was closely related to the wastewater discharge in adjacent areas.
This study reconstructed the local heavy metal pollution history and provides important information for environmental protection and policy making.
... For alluvial rivers and reaches, Caskey et al. (2015) reported that channel simplifying and narrowing could occur because of diversion-induced flow alterations in single-thread, straight and meandering, alluvial channels on low to moderate gradient (<3%) valley segments. Wang et al. (2008) predicted that sediment deposition would develop along the whole reach in the long term downstream of the large water diversions in the Lower Yellow River. In general, these studies illustrate that the morphological responses of the downstream channels to the diversions are not only related to the changes in flow regimes and sediment availability, but also to the bed types and channel slope and geometry. ...
A recent study reported considerable sediment trapping by three large channel bars downstream 18–28 km of the Mississippi–Atchafalaya River diversion (commonly known as the Old River Control Structure, ORCS) during the 2011 Mississippi River flood. In this study, we analyzed 3-decadal morphological changes of the 10-km river channel and the three bars to elucidate the long-term effects of river engineering including diversion, revetment and dike constructions. Satellite images captured between 1985 and 2015 in approximate 5-year intervals were selected to estimate the change of channel morphology and bar surface area. The images were chosen based on river stage heights at the time when they were captured to exclude the temporal water height effect on channel and bar morphology. Using a set of the satellite images captured during the period of 1984–1986 and of 2013–2014, we developed rating curves of emerged bar surface area with the corresponding river stage height for determining the change in bar volume from 1985 to 2013. Two of the three bars have grown substantially in the past 30 years, while one bar has become braided and its surface area has shrunken. As a whole, there were a net gain of 4,107,000 m2 in surface area and a net gain of 30,271,000 m3 in volume, an equivalent of approximately 36 million metric tons of sediment assuming a bulk density of 1.2 t/m3. Sediment trapping on the bars was prevalent during the spring floods, especially during the period of 1990–1995 and of 2007–2011 when large floods occurred. The results suggest that although revetments and dikes have largely changed the morphology of the channel and the bars, they seem to have a limited impact on the overwhelming trend of sediment deposition caused by the river diversion.
... Water diversion projects can also change downstream hydrological regimes. In a theoretical morphological analysis conducted by Wang et al. (2008), they show that large scale diversions like those along the lower Yellow River can, in the longterm , cause the development of a convex riverbed profile. Deposition will take place along the whole reach of the river, with an increasing deposition depth from downstream to upstream. ...
Water is a basic necessity for organisms living on the earth. Most organisms, including humans, consist mainly of water and live on a planet that is dominated by water. Yet, despite this global abundance of water and its renewable characteristics, as much as one-fifth of the world’s population lives under conditions of water scarcity. This scarcity is due primarily to the heterogeneous distribution of freshwater in space and time. The availability of water is an important factor in determining the distribution of human populations, but historical, social, political, and institutional factors may contribute to situations where large groups of people suffer from shortages of fresh water.
... where g is gravitational acceleration; h and ū are average flow depth and flow velocity at Huayuankou, respectively; C Si is simulated average volumetric suspended sediment concentration at Huayuankou; ρ s is sediment density; and κ, ρ m , and w Sm are the von Karman constant, the density of the water-sediment mixture, and sediment settling velocity in the water-sediment mixture, respectively. Equation (7) considers the effects of suspended sediment concentration on the sediment-carrying capacity [Wang et al., 2008b], making it a suitable equation for historical periods with significant differences in sediment load. ...
The Yellow River, China, experienced >1000 levee breaches during the last 3000 years. A reduced-complexity model is developed in this study to explore the effects of climate change and human activity on flood levels, levee breaches, and river avulsions. The model integrates yearly morphological change along a channel belt with daily river fluxes and hourly evolution of levee breaches. Model sensitivity analysis reveals that under natural conditions, super-elevation of the channel belt dominates flood frequency. When there is significant human-accelerated basin erosion and breach repair, the dominant factors shift to a combination of mean annual precipitation, super-elevation, critical shear stress of weak channel banks, and the time interval between breach initiation and its repair. The effect of precipitation on flood frequency is amplified by land use changes in the hinterland, particularly in the erodible Loess Plateau. Uncertainty analysis estimates the most likely values of the dominant factors for six historical periods between 850 BC and AD 1839, which are used to quantitatively reconstruct flood dynamics. During 850 BC to AD 1839, when the sediment load increased fourfold, the breach recurrence interval was shortened from more than 500 years to less than 6 years, and the breach outflow rate increased ~27 times. River management practices during AD 1579 to AD 1839 focused on levees and triggered a severe positive feedback of increased levee heights and flood hazard exacerbation. Raising the levee heights proved to be ineffective for sustainable flood management.
... The flow-sediment interaction, particularly bed forms, plays a minor role. However, Kerssens and Van Urk (1986), Neary et al. (1993), Belaud and Paquier (2001), Michell et al. (2006), Wang et al. (2008), and Izadpanah et al. (2010) investigated the interaction of flow and sediment transport in case of lateral water withdrawal. ...
In flood protection engineering, side weirs or overflow dams are used to divert water in a controlled way into flood plains as soon as the discharge capacity of the main-channel is reached. Because of the lateral loss of water, the sediment transport capacity is reduced, resulting in local sediment deposition near the side overflow. Moreover, bed form characteristics such as length, height, steepness, and stoss and lee slope angle are affected by the lateral water withdrawal. Both phenomena are responsible for an increased side overflow intensity compared with plane bed conditions. The results from a systematic flume study show that the shape of observed bed forms is highly three-dimensional and that three distinct regions along the channel axis can be identified. The first one extends from the channel entrance to the upstream weir corner, the second one comprises the reach of the weir, and the third one represents the reach downstream of the weir. The description of bed form shape by approaches from literature shows reasonable agreement with measured bed form geometry.
... Currently, there are many different monthly water balance models available in the literature (Guo and Wang, 1994;Xu and Singh, 1998;Xiong and Guo, 1999;Wang et al., 2005). Such models have been used to study the impact of climate change (or human activity) on the hydrological balance, and also for studies related to general water resource planning and management (Wang et al., 2008b;Xu, 1999). The more complex the hydrological model, the higher the intercorrelation between model parameters (Vandewiele et al., 1992;Wang et al., 2005), and hence a physically based simple conceptual watershed model with fewer parameters may be better able to regionalize model parameters. ...
Prediction in ungauged basins remains a major challenge in hydrology. A key issue in the application of hydrological models to ungauged areas is regional parameterization. This paper presents a regional calibration approach to constructing regional relationships between the parameters of the Snowmelt-based Water Balance Model (SWBM) and catchment characteristics. Data from 38 well-gauged catchments were used to establish regional regression equations of model parameters, and data from an additional four independent catchments were used to test and validate the proposed regional calibration approach. The results indicated that the SWBM performed well in monthly discharge simulations for the 38 well-gauged catchments. The regional relationships of the SWBM parameters derived from the regional calibration approach were found to be highly correlated to catchment characteristics. In addition, the SWBM performed well in discharge simulations for the additional four test sites using only the constructed regional equations to estimate model parameters.
... These model results are consistent with the results of previous studies based on field measurements, satellite image and historical chart analysis. As previous studies have pointed out (Dronkers, 1985;Wang et al., 2002;Van der Wegen and Roelvink, 2008;Wang et al., 2008;Xie et al., 2009), negative feedback mechanisms exist between flow, sediment transport and bathymetry which are responsible for macro-scale morphodynamic evolution of the estuary. The long-term morphological evolution in the timescale of years is related to short-term hydrodynamics and sediment transport on a timescale of a tidal period. ...
A 2D depth-averaged numerical model is set up to simulate the macro-scale hydrodynamic characteristics, sediment transport patterns and morphological evolution in Hangzhou Bay, a large macro-tidal estuary on the eastern coast of China. By incorporating the shallow water equations, the suspended sediment transport equation and the mass-balance equation for sediment; short-term hydrodynamics, sediment transport and long-term morphological evolution for Hangzhou Bay are simulated and the underlying physical mechanisms are analyzed. The model reproduces the spatial distribution patterns of suspended sediment concentration (SSC) in Hangzhou Bay, characterized by three high SSC zones and two low SSC zones. It also correctly simulates the residual flow, the residual sediment transport and the sediment accumulation patterns in Hangzhou Bay. The model results are in agreement with previous studies based on field measurements. The residual flow and the residual sediment transport are landwards directed in the northern part of the bay and seawards directed in the southern part. Sediment accumulation takes place in most areas of the bay. Harmonic analysis revealed that the tide is flood-dominant in the northern part of the bay and ebb-dominant in the southern part of the bay. The strength of the flood-dominance increases landwards along the northern Hangzhou Bay. In turn sediment transport in Hangzhou Bay is controlled by this tidal asymmetry pattern. In addition, the direction of tidal propagation in the East China Sea, the presence of the archipelago in the southeast and the funnel-shaped geometry of the bay, play important roles for the patterns of sediment transport and sediment accumulation respectively.
... These model results are consistent with the results of previous studies based on field measurements, satellite image and historical chart analysis. As previous studies have pointed out (Dronkers, 1985;Wang et al., 2002;Van der Wegen and Roelvink, 2008;Wang et al., 2008;Xie et al., 2009), negative feedback mechanisms exist between flow, sediment transport and bathymetry which are responsible for macro-scale morphodynamic evolution of the estuary. The long-term morphological evolution in the timescale of years is related to short-term hydrodynamics and sediment transport on a timescale of a tidal period. ...
A 2D depth-averaged numerical model is set up to simulate the macro-scale hydrodynamic characteristics, sediment transport patterns and morphological evolution in Hangzhou Bay, a large macro-tidal estuary on the eastern coast of China. By incorporating the shallow water equations, the suspended sediment transport equation and the mass-balance equation for sediment; short-term hydrodynamics, sediment transport and long-term morphological evolution for Hangzhou Bay are simulated and the underlying physical mechanisms are analyzed. The model reproduces the spatial distribution patterns of suspended sediment concentration (SSC) in Hangzhou Bay, characterized by three high SSC zones and two low SSC zones. It also correctly simulates the residual flow, the residual sediment transport and the sediment accumulation patterns in Hangzhou Bay. The model results are in agreement with previous studies based on field measurements. The residual flow and the residual sediment transport are landwards directed in the northern part of the bay and seawards directed in the southern part. Sediment accumulation takes place in most areas of the bay. Harmonic analysis revealed that the tide is flood-dominant in the northern part of the bay and ebb-dominant in the southern part of the bay. The strength of the flood-dominance increases landwards along the northern Hangzhou Bay. In turn sediment transport in Hangzhou Bay is controlled by this tidal asymmetry pattern. In addition, the direction of tidal propagation in the East China Sea, the presence of the archipelago in the southeast and the funnel-shaped geometry of the bay, play important roles for the patterns of sediment transport and sediment accumulation respectively.
... Moreover, the water flow into the sea was reduced, thus influencing the existence and reproduction of fish. Water transfer projects have proven that water transfer can result in serious problems, such as seawater invasion, the decline of water quality, sediment, erosion, destruction of the water ecosystem, inundation of large areas of land, involuntary resettlement, and third-party influences [5]. Usually, larger long-distance water transfer projects can elicit complex eco-environment effects. ...
The planning Yalong-River water transfer project will transfer 5.65 billion cubic meters water from the Yalong River into the Yellow River per year. The Yalong River will be dramatically impacted hydrologically and ecologically because more than 60% of the runoff will be diverted. An ecohydrological model was used to evaluate the impacts of the project on river corridor and wetland in this study. Schizothorax is a typical plateau river species and was used as the indicator species for assessment of the impact of water transfer project. The model simulated the habitat area of Schizothorax in the reach between the Reba Dam and the Ganzi Hydrology Station on the Yalong River. The Reba Dam, A’an Dam and Renda Dam will be constructed in the Yalong River for enhancing the water level for water diversion into the Yellow River. The velocity, channel width, runoff, and water depth will be reduced due to the water transfer, especially during flood season. The reduction in the velocity, channel width, runoff and water depth will occur mainly in the reach near the three dams and the reduction will be reduced to a minimum level in a distance about 100 km downstream of the dams. The maximum net water loss of Kasha Lake is only 1197200 m3, only 0.3% of runoff flowing into the lake. The project cannot bring adverse effect on the lake. The habitat area of Schizothorax in the Yalong River might be reduced if the water was transferred from the Reba Dam. The habitat area of this species will be reduced more than 40%.
... A large number of estuarine deltas have suffered from erison or have had reduced accretion rates because human intervention in the catchments which eliminated the sediment supply to the estuary (Liu et al., 2008;Wang et al., 2008). Thus, numerous studies have been undertaken to investigate the changes in the estuarine systems due to human activities, including investigations on the Nile River (Fanos, 1995), the Chinese Changjiang and Huanghe Rivers (Yang et al., 2004(Yang et al., , 2005Xu, 2003), the Spanish Ebro River (Mikhailova, 2003), the European Danube River (Panin and Jipa, 2002), the French Rhone River (Fassetta, 2003), the Finnish Kokemaenjoki River (Ojala and Louekari, 2002), the Russian Don River (Mikhailov et a1., 2001), the African Niger River (Abam, 1999), the Volta River (Ly, 1988), the Senegal River (Barusseau et a1., 1998), and the American Skokomish River (Jay and Simenstad, 1996). ...
The response of the Yalu River Estuary to human activities was investigated. Changes of sediment dynamics during the past 10 years were explored through hydrodynamic calculation, as well as heavy mineral and grain size analysis. In addition, the characteristics of estuarine geomorphological evolution were compared with historical data. The long-term sediment dynamic process and geomorphological evolution were primarily affected by the decrease of water discharge and sediment supply resulting from human activities. The entire estuarine system of Yalu River Estuary has also undergone significant changes since 1941 that are associated with water reduction and sediment discharge affected by construction reservoirs. The estuary eventually formed the current patterns in the 1980s. Compared with variations of water and sediment discharge, sand dredging directly affected the estuarine sediment dynamics in the past 10 years. Data from six hydrodynamic stations measured in 2009 indicated that the bedload transport flux has substantially decreased during a tidal cycle compared with that surveyed in 1996. The bedload transport direction also changed from seaward in 1996 to landward in 2009. In addition, the estuarine bed load movement changes were: (a) sediment from areas with water depth being less than 5 m was transported from the sea towards the land; (b) sediment transport from areas with water depth between 5 to 20 m was oriented towards the sea; and (c) sediment from areas with water depth greater than 20 m was conveyed from the sea towards the land.
... Large numbers of source substances under the combined action of marine agent and runoff accumulated rapidly to form the protruding sandspit and the subaqueous deltaic accumulating body of rapid growth (Yu, 2002). The high silt content and rapid deposition caused the frequent diversion or shift of the river course (Wang et al., 2008). After river diversion, the abandoned lobe would be eroded by waves and eventually regress due to the loss of sediment sources (Li et al., 1998). ...
Coastal structures in tidal estuaries are of scientific and societal interest as they form important artificial sea barriers resulting in different hydrodynamic conditions on both sides of them. A field study was performed on both sides of an embankment in the Yellow River Delta, China, in order to investigate the temporal and spatial variations in the geotechnical strength of the sediment caused by the effects of different hydrodynamic conditions. Using a portable core penetration tester together with hydrodynamic observation and fractal dimension analyses, changes in sediment strength were tested in 1999 and 2002 in rectangular areas on both sides of the embankment and along two cross-shore profiles. The field observations both on space and time scales suggest that different intensity in wave loading can not change the mean strength of the superficial sediment within 0–15cm depth, but rather makes it more uneven under strong hydrodynamic conditions, with the increasing degree of heterogeneity that can be quantitatively described by the fractal method. The effect of waves is regarded as the major control factor on the quasi-periodic alternation of sediment strength within the study area surface and the depth stratification in the Yellow River Delta. Further work is still necessary to determine the forming process, its mechanism and their implications for efficient environmental management, coastal protection and hazard forecasting.
... This effect can be estimated by rewriting the Chezy equation in combination with a simple powerlaw sediment transport formula ͑relating the transport s to velocity u to the power n͒. The response of the equilibrium river bed slope i to changes in the specific discharge q of a river ͑see Wang et al. 2008b͒ is then given as ...
The high sediment load of the Yellow River results in rapid infilling of its reservoirs when sediment is not regularly flushed. Simultaneously, the downstream reaches of the Yellow River experience extremely high siltation rates, which are reduced when sediment is retained in its reservoirs. To minimize siltation in the reservoirs and the downstream river bed, water and sediment are released from the reservoir in a controlled way through flushing experiments. In this paper, we analyze the effect of such a flushing event on the downstream river bed through data analysis and numerical modeling. Sedimentation may be minimized by relating the amount of sediment released from the reservoir to the sediment available for release through operational monitoring and by releasing relatively clear water after turbid water. Despite this flushing of sediment, the reservoir will eventually fill up, and more sediment released again into the lower Yellow River. The change in discharge magnitude and frequency brought about by the reservoir will then probably result in increased siltation rates in the lower Yellow River compared to the predam situation.
... Hyperconcentrated floods occur less frequently than in the 1960s and 1970s. The fluvial processes are now affected both by hyperconcentrated floods and water and sediment load reduction ( Wang et al., 2008). This paper presents new results of studies on the phenomena and mechanisms of sediment transportation, fluvial processes, and the impact on river morphology of hyperconcentrated floods. ...
Hyperconcentrated floods, with sediment concentrations higher than 200 kg/m3, occur frequently in the Yellow River and its tributaries on the Loess Plateau. This paper studies the fluvial hydraulics of hyperconcentrated floods by statistical analysis and comparison with low sediment concentration floods. The fluvial process induced by hyperconcentrated floods is extremely rapid. The river morphology may be altered more at a faster rate by one hyperconcentrated flood than by low sediment concentration floods over a decade. The vertical sediment concentration distribution in hyperconcentrated floods is homogeneous. The Darcy–Weisbach coefficient of hyperconcentrated floods varies with the Reynolds number in the same way as normal open channel flows but a representative viscosity is used to replace the viscosity, η. If the concentration is not extremely high and the Reynolds number is larger than 2000, the flow is turbulent and the Darcy–Weisbach coefficient for the hyperconcentrated floods is almost the same as low sediment concentration floods. Serious channel erosion, which is referred to as ‘ripping up the bottom’ in Chinese, occurs in narrow-deep channels during hyperconcentrated floods. However, in wide-shallow channels, hyperconcentrated floods may result in serious sedimentation. Moreover, a hyperconcentrated flood may cause the channel to become narrower and deeper, thus, reducing the flood stage by more than 1 m if the flood event lasts longer than one day. The fluvial process during hyperconcentrated floods also changes the propagation of flood waves. Successive waves may catch up with and overlap the first wave, thus, increasing the peak discharge of the flood wave during flood propagation along the river course. Copyright © 2009 John Wiley & Sons, Ltd.
Climate change, river pollution and loss of biodiversity are increasing and becoming global environmental concerns. The Yellow River is China’s mother river, providing water for about 114 million residents in towns and cities along its route. Yet in 2012, the Yellow River received 4.474 × 109 tons of sewage containing a large number of exogenous pollutants, posing a huge ecological and public health threat. Water quality safety is not only a matter of ecosystem health but also of human survival and social development. Therefore, the effects of pollutants on water quality safety should be carefully studied, which is important to ensure the sustainability of the Yellow River and the surrounding cities and towns. In this study, water and sediment samples from the Jishan River of the Juancheng, a typical city in the lower reaches of the Yellow River, were collected and evaluated by integrating the traditional physicochemical water indicators, benthic Index of Biological Integrity (B-IBI) and zebrafish embryotoxicity test. The results showed that water dissolved oxygen, pH, total nitrogen and total phosphorus were strongly correlated with zebrafish embryonic teratogenicity, lethality, abundance index and Shannon Winner index. A total of 21 benthic species were collected, including mollusks, arthropods and annelids, with the upper reaches having the largest biomass and B-IBI values indicating the urban reaches have better biological integrity than rural reaches. The teratogenic rate of zebrafish embryos in raw water was greatest in rural rivers and was significantly different from the negative control (p < 0.05). When exposed to 100 mg/mL sediment samples, embryo hatching rates were inversely correlated with teratogenic rates, with lethal rates reaching over 96% in all rural reaches. The results showed that the water quality safety at the rural farms in the Yellow River transfer-type towns is poor, and they especially recommended that the river near the farms in rural areas should be monitored with emphasis.
Palaeodischarge estimation is largely undertaken within fluvial settings. However, there are limited palaeodischarge estimates specifically from delta deposits, despite their significance globally. Estimating water palaeodischarges for deltas using catchment‐based approaches developed using data from fluvial settings requires estimating parameters from the rock record (for example, palaeotemperature, palaeoslope and palaeorelief). These may be difficult to determine, leading to under‐estimation or over‐estimation of palaeodischarge values due to differences in process‐form relationships between alluvial rivers and deltas. When a sediment‐conveying fluvial channel enters a standing body of water, delta lobes develop through repeating mouth bar deposition due to flow deceleration, forming a deltaic morphology with distributary channel networks that differ morphologically from those developed in unidirectional flowing alluvial rivers. This study provides empirical relationships determined across five climate regions, using 3823 measurements of distributary channel width from 66 river deltas alongside the trunk river bankfull discharge that feeds into the entire delta, using a hydraulic geometry scaling approach. Empirical relationships are developed from the global delta dataset between bankfull discharge and catchment area (Qb–A), and bankfull discharge and median distributary channel width (Qb–Wmed). These empirical relationships produce very strong statistical correlations, especially between Qb and Wmed, across different climate regions (Qb = 0.34Wmed1.48, R2 = 0.77). However, both Qb–A and Qb–Wmed relationships have outliers that may be explained by particular hydrological or geomorphic conditions. These new empirical relationships derived from modern systems are then applied to Cretaceous outcrops (Ferron Sandstone and Dunvegan Formation). The comparatively simple scaling relationships derived here produced palaeodischarge estimates within the same order of magnitude as palaeodischarge values previously obtained using existing, more complex approaches. This study contributes to source‐to‐sink investigations by enabling palaeodischarge estimates that intrinsically account for climate impacts on channel geometry at the time of deposition, using measurements of channel width or catchment area of a deltaic outcrop.
The hydrology and sediment processes in large rivers play important roles in maintaining aquatic and coastal ecosystems and advancing civilization and production in human systems. Therefore, quantitatively analyzing the spatiotemporal variability and dynamics of water and sediment discharge in large rivers is essential for improving watershed management and sustainable development in the areas surrounding rivers, especially the Yellow River, which is one of the most sediment-laden rivers in the world. In this study, we analyzed the evolution patterns and spatial sources of water and sediment discharge in the Yellow River from 1951 to 2020 and determined the impacts of different factors on water and sediment discharge variations. The results showed that the annual water and sediment discharge significantly decreased (p < 0.05) over the past 70 years, with an abrupt change occurring in 1986. The first dominant periodicity of water discharge was approximately 29 years, while the first dominant periodicity of sediment discharge was approximately 28 years. In terms of the water and sediment sources, the dominant factor affecting variations in water discharge was water diversion from 1951 to 2020, while the dominant factor affecting variations in sediment discharge was sediment aggradation from 1951 to 1985 and changed to tributary inflow sediment from 1986 to 2020. In addition, the water and sediment discharge changes were also affected by anthropogenic activities, such as water and sediment diversions, dams and reservoirs, and water and soil conservation measures. In particular, the water and sediment interception capabilities of the established soil and water conservation measures gradually became saturated over time. Specifically, the maximum water and sediment interception capabilities of the current soil and water conservation measures were 12.2 billion m³ and 1.9 Gt, respectively. Overall, the results of the present study can help tailor water and sediment regulation countermeasures in the future.
Water diversion rivers are the fundamental transport lines in water diversion projects, which represent a unique ecosystem with changeable hydrological and physicochemical conditions, leading to significantly changes in biogeographical characteristics of microbial communities within river catchments. This study gives an insight into longitudinal patterns of the composition and diversity characteristics of microbial communities in water diversion rivers in the East Route of the South‐to‐North Water Diversion Project using 16S rRNA gene‐based Illumina MiSeq sequencing. A total of 937 743 microbial sequence reads were obtained and classified into 9178 distinct operational taxonomic units, belonging to 48 phyla and 424 genera, respectively. Along the water diversion line, obvious distribution characteristics of microbial communities could be observed in Actinobacteria, Firmicutes, Exiguobacterium, CL500‐29_marine_group, Acinetobacter, and Cloacibacterium. The relative abundance of Actinobacteria and CL500‐29_marine_group both increased from the upper rivers in the northern region to the lower rivers in the southern region, while Firmicutes and Exiguobacterium showed the opposite trend. Ammonia oxidizers were the most abundant functional group, followed by dehalogenators, sulfate reducers, and nitrite reducers. Higher microbial diversity was found in the upper rivers of the water diversion line than in the lower rivers. Externally, redundant analysis indicated the spatial shift in microbial community is largely shaped by ammonium, total nitrogen, conductivity and total phosphorus. Internally, longitudinal construction of the microbial community was mainly affected by species replacement. This article is protected by copyright. All rights reserved
Deltas are classified into river-, wave-, and tide- dominated deltas according to the dominant forces; or fan deltas and braided deltas according to their geomorphic settings. Large river deltas can also be classified into male deltas and female deltas. Estuary floods are due to 1) subsidence of the land or islands; 2) tsunamis, hurricanes and storm surges; and 3) heavy rainstorms. The flooding risk and flood defense strategies are discussed with the Venice Lagoon, Indian Ocean Tsunami, Hurricane Kartrina and New Orleans, and Hong Kong as examples. Human activities pose a serious threat to the health of estuaries and coastal waters. In particular, semi-enclosed estuaries are often under pressure to serve as wastewater disposal areas, leading to a high risk of eutrophication and algal blooms. Wastewater is flushed through repeated exchange of the intertidal water volume between the embayment and the open water body: clean water entering the embayment during flood tide fills the intertidal volume, mixing with the existing water in the embayment and, as the tide falls, the intertidal volume of water discharges out of the embayment, removing the dissolved substance. Tidal flushing time is taken as the time required for a tracer mass to reduce to a certain level of the initial mass. Wetlands along coastal shorelines serve as natural barriers against flood damage and erosion due to wind, waves and currents. Mangrove plants are capable of transferring oxygen from the atmosphere to the roots and creating an oxygenated zone for nitrification around the roots while the surrounding sediments are reduced thus favoring de-nitrification. Various techniques of wastewater outfalls, protection of wetlands, and prediction of algal blooms are also discussed in this chapter.
The runoff and sediment in the Yellow River Delta is significant to the continuous economic development and ecological environment evolution. The analysis of the flow and sediment can provide an important basis for the future control of the River Delta. According to the survey data from 1950∼2007 of Linjin hydrologic station, probability statistics and time series method such as Kendall method, order clustering method are applied to analyze the runoff and sediment discharge. The results show that the flow and sediment have been declining obviously over the past 60 years, and the change decreases mainly in the form of jumping. The reasons of the variations of flow and sediment are also discussed in this paper. © 2012 by International Society of Offshore and Polar Engineers.
A simulation for floc growth in three-dimensional space is presented with diffusion-limited aggregation model. In three-dimensional space, calculation methods of fractal dimension for non-uniform sediment flocs are deduced from density function method, radius of gyration method and sedimenation method, respectively. Fractal dimensions are calculated using diffusion-limited aggregation model. Results obtained show that the fractal dimensions calculated by three methods are all at the range of 1.75 to 2.19. However, the fractal dimensions calculated by radius of gyration method are little greater than those by density function method and sedimenation method. The fractal dimensions calculated from non-uniform sediment flocs are greater than those of uniform sediment flocs, and they are both decreased with the increase of floc size. Researches presented have some theoretical and practical meanings on the control and treatment of the Yellow River high turbidity flow.
In recent years, promoted by tremendous demands from national economic construction, great progress has been made in geomorphology and Quaternary geology in China. This article generalizes the recent progresses, mainly those in the period 2006-2008, including the progress in the fields of tectonic landforms, fluvial landforms, eolian landforms, glacial landforms, estuary and coastal landforms and Quaternary environmental evolution. Furthermore some suggestions are proposed to develop the discipline in the following aspects: (1) Studies of basic theories; (2) Research into applied geomorphology and Quaternary geology concerning the key construction projects; (3) Experimental studies, both in laboratories and in field surveys; (4) Training of young geomorphologists and Quaternary geologists.
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.
A coupled routing for the transport capacity and the energy slope is introduced through the definition of the control factor m whose value is linked to the bed form configuration. The coupling aims to further incorporate the interactions occurring in alluvial rivers and thus enhance the prediction of the fine sediment fluxes, especially during high stream power events. Based on a predictive rule for the control factor m that only involves water depth, velocity and bedform constitutive texture, the novel method is confronted to observations collected in one of the most strongly dynamic alluvial river namely the Lower Yellow River. Comparisons between time series of measured and computed concentrations illustrate that during high velocity events the main dynamics of the sediment transport is correctly reproduced. The main advantage of the present approach is to supply consistent time evolutions of sediment concentrations without making use of any detailed shear information.
The Yellow River is widely known as a “hanging river” due to its high sedimentation rate (the current channel bed is about 2.74m higher than the overbank plains on average) in the lower reach. Understanding the variations in channel patterns and their influencing factors is crucial to regulate potential flooding risk in this critical region. Changes in discharge, suspended sediment delivery rate, median grain size, sedimentation rate, channel planform and cross-section, and channel width/depth ratio during 1950–1999 from gauging stations in Huayuankou, Gaocun-Sunkou and Lijin that represent the braided, meandering and straight channel sections, respectively, were compared. During this period, frequent internal channel variations dominated in the braided channel section. The channel bed was continuously raised as a whole, but experienced strong erosion in certain times, mainly influenced by the operation and closure of the Sanmenxia Dam. The straight channel section was relatively stable due to restricted lateral migration by the solid artificial levees in both banks. Instead, channel aggradation was the dominant process and erosion only happened when channel avulsions occurred in the river mouth. The meandering channel section between the upstream braided and downstream straight channel sections was formed as a result of stream self-adjustment. Rapid lateral migrations were observed during this period, but the extent of the migration was restricted by artificial levees. Sediment aggradation on the channel bed and floodplain was apparent. Since 1970, the channel shrank remarkably in all sections due to the increased use of water resources and the decreased precipitation in the Yellow River basin. Recently, migration of the channel is limited, and the lower portion of the braided section seems to be a meandering channel.
A new closure approach involving a common parameter has been incorporated into a 1D fully coupled model of mobile-bed alluvial hydraulics. The objective is to simplify the methodology of 1D river routing models and to improve their accuracy. The common parameter, called control factor m, introduces the concept of Rossiter modes in alluvial hydraulics and represents the interactions between the flow, the sediment transport and the bed morphology. The feasibility of the new closure approach has been established by reproducing numerically the 2002 silt flushing experiment conducted on the Lower Yellow River (LYR) downstream the Xiaolangdi reservoir. From the comparison between the experimental data and the numerical results, a time evolution of the control factor m reproducing the characteristics of the flow has been extracted. This time evolution agrees with analysis conducted previously on other datasets and with data measured during the flush. The results obtained with this time evolution for the hydraulics, the sediment transport and bed adaptation are encouraging but still need improvements and further feeding from complementary experimental data.
Ab initio calculations have been performed at the UMP2/aug-cc-pVDZ and UMP2/aug-cc-pVTZ levels to study the non-additivity of methyl group in the single-electron halogen bond. The strength of the interaction in the CH3–BrH, CH3CH2–BrH, (CH3)2CH–BrH, and (CH3)3C–BrH complexes has been analyzed in terms of the geometries, energies, frequency shifts, stabilization energies, charges, and topological parameters. tert-Butyl radical forms the strongest halogen bond, followed by iso-propyl radical and then ethyl radical, methyl radical forms the weakest halogen bond. The shortening of the C···Br distance and increase of the binding energy in the (CH3)2CH–BrH and (CH3)3C–BrH complexes are more than two and three times those in the CH3CH2–BrH complex, respectively. A positive non-additivity is present among methyl groups. Such conclusions have also been estimated with natural bond orbital (NBO) and atom in molecules (AIM) analyses. The orbital interaction and charge transfer play an important role in the non-additivity of methyl groups.
This paper presents simulated channel patterns for various scenarios in a conceptual alluvial valley by an improved two-dimensional (2-D) mathematical model described in the companion paper. Starting from the same initial channel, different channel patterns have been simulated over a real time period of 250 days for varied boundary and initial conditions, including the inlet water discharge and sediment load, initial valley slope, and erodibility of river banks. Impacts of these control factors are discussed, in terms of the longitudinal bottom profiles of simulated fluvial channels, the geometry of channel cross sections, and the water surface profiles in the conceptual river valley. Results suggest that the upper and lower parts of the same channel may have different planforms because the sediment transport conditions of the two parts differ greatly. Simulated causal relationship between control variables and channel patterns agrees qualitatively with known channel pattern theories.
The availability of nearly 100 years of bathymetric measurements allows the analysis of the morphodynamic evolution of the Dutch Wadden Sea under rising sea level and increasing human constraint. The historically observed roll-over mechanisms of landward barrier and coastline retreat cannot be sustained naturally due to numerous erosion control measures that have fixed the tidal basin and barrier dimensions. Nevertheless, the large continuous sedimentation in the tidal basins (nearly 600 million m3), the retained inlets and the similar channel-shoal characteristics of the basins during the observation period indicate that the Wadden Sea is resilient to anthropogenic influence, and can import sediment volumes even larger than those needed to compensate the present rate of sea-level rise. The largest sedimentation occurs in the Western Wadden Sea, where the influence of human intervention is dominant. The large infilling rates in closed-off channels, and along the basin shoreline, rather than a gradual increase in channel flat heights, render it likely that this sedimentation is primarily a response to the closure of the Zuiderzee and not an adaptation
to sea-level rise. Most of the sediments were supplied by the ebb-tidal deltas. It is, however, unlikely that the sediment volume needed to reach a new equilibrium morphology in the Western Wadden Sea can be delivered by the remaining ebb-tidal deltas alone.
A large amount of the total sediment load in the Chinese Yellow River is transported during hyperconcentrated floods. These floods are characterized by very high suspended sediment concentrations and rapid morphological changes with alternating sedimentation and erosion in the main channel, and persistent sedimentation on the floodplain. However, the physical mechanisms driving these hyperconcentrated foods are still poorly understood. Numerical modelling experiments of these floods reveal that sedimentation is largely caused by a collapse of the turbulence structure by sediment-induced density gradients, whereas erosion prevails when this sediment is largely held in suspension due to hindered settling. Observed patterns of erosion and sedimentation during these floods can be well reproduced using a numerical model in which sediment-induced density effects and hindered settling are included. Based on these results a refined definition of hyperconcentrated flow is proposed.
Soil loss, water shortage, flooding, sedimentation and water pollution are the major problems affecting the sustainable development of the Yellow River basin. Their impacts and management strategies are briefly discussed in this paper. The integrated management strategy, which includes one ultimate goal, four standards, nine countermeasures, and the concept of “three Yellow Rivers,” is a contemporary management strategy and represents the vision of the Chinese government and engineers for the sustainable development of the Yellow River basin.
In the past 30 years, the lower Yellow River has been watching obvious variation in water and sediment load, which has caused the readjustment of longitudinal and transversal river bed profiles. This article studies the characteristics of the water and sediment load from 1960 to 1997 and the longitudinal and transversal bed profile from 1977 to 2002 by employing statistic analysis. The main results are: i) Water and sediment load and their fluctuation decreases sharply after 1986. The river is dried up very often in the reach from Aishan to Lijin; ii) The longitudinal profile of the lower Yellow River is developing toward an S shape; iii) The wet area of the stem channel of the lower Yellow River becomes smaller.
It is important to know the rate of intra-molecular contact formation in proteins in order to understand how proteins fold clearly. Here we investigate the rate of intra-molecular contact formation in short two-dimensional compact polymer chains by calculating the probability distribution p(r) of end-to-end distance r using the enumeration calculation method and HP model on two-dimensional square lattice. The probability distribution of end-to-end distance p(r) of short two-dimensional compact polymers chains may consist of two parts, i.e. p(r) = p1(r) + p2(r), where p 1(r) and p2(r) are different for small r. The rate of contact formation decreases monotonically with the number of bonds N, and the rate approximately conforms to the scaling relation of k(N) ∝ N -α, Here the value of α increases with the contact radius α and it also depends on the percentage of H (hydrophobic) residues in the sequences of compact chains and the energy parameters of εHH εHp and εPP. Some comparisons of theoretical predictions with experimental results are also made. This investigation may help us to understand the protein folding.
Small runoff, large sediment load, and incompatible relationship of flow and sediment load are very important characteristics of the Yellow River. They are also the crux of the most prominent problems of the Yellow River. To solve these problems, the regimes of flow and sediment load have to be improved by increasing water, reducing sediment load, and by using reservoirs to regulate flow and sediment load. The results of experiments for regulating the flow and sediment load in the last three years by the Xiaolangdi Reservoir have indicated that this measure is a realistic and effective way to mitigate the prominent problems in flood control of the Lower Yellow River at present and in the near future. However, the regulation system is still imperfect. It is advisable to speed up the pace of research and construction of the system for regulating flow and sediment load.
PROCESSES ON DEGRADATION AND AGGRADATION OF RIVERS HAVE A SPEED DEPENDING ON THE CHARACTERISTICS OF THE RIVERS.STARTING FROM THE BASIC EQUATIONS A MORPHOLOGICAL TIME-SCALE, CHARACTERISING THESE PROCESSES, IS DEFINED.THIS MORPHOLOGICAL TIME-SCALE IS ESTIMATED FOR VARIOUS RIVERS.(A.)
The cross-sectional stability of two tidal inlets connecting the same back-barrier lagoon to the ocean is investigated. The condition for equilibrium is the cross-sectional area tidal prism relationship. In an earlier study [Van de Kreeke, J., 1990. Can multiple inlets be stable Estuarine, Coastal and Shelf Science 30: 261-273.], using the same equilibrium condition, it was concluded that where two inlets connect the same basin to the ocean ultimately one inlet will close. One of the major assumptions in that study was that the water level in the basin fluctuated uniformly. In hindsight this assumption might be too restrictive. For example, in the Wadden Sea the back barrier lagoon consists of a series of basins, rather than one single basin, separated by topographic highs. These topographic highs limit but do not exclude the exchange of water between the sub-basins. For this reason in the present study, a topographic high in the form of a weir was added, separating the back-barrier lagoon in two sub-basins. The water level in the sub-basins, rather than in the back-barrier as a whole, is assumed to fluctuate uniformly. For this schematization the hydrodynamic equations are solved using a finite difference method. The results, together with the equilibrium condition, yield the equilibrium flow curve for each of the inlets. The intersections of the two equilibrium flow curves represent combinations of cross-sectional areas for which both inlets are in equilibrium. The stability of the equilibriums was investigated using a non-linear stability analysis resulting in a flow diagram. Calculations were carried out for different inlet and weir characteristics. Sinussoidal tides were the same for both inlets. The results show that for relatively large wetted cross-sectional areas over the topographic high, approaching the situation of a single basin, there are no combinations of inlet cross-sectional areas for which both inlets are in a stable equilibrium. This supports the conclusion in the earlier study. For relatively small wetted cross-sectional areas over the topographic high there is one set of stable equilibriums. In that case the two-inlet bay system approaches that of two single-inlet bay systems.
This chapter discusses the morphodynamic evolution of tidal basins and coastal inlets, which is a complex issue. Due to the complexity, scientific attention is spent on uninterrupted coasts and rivers. Ecologically and socio-economically tidal basins and coastal inlets are of high importance. The derivation in the chapter explains that tidal basins with relatively shallow channels require relatively wide flats, and that tidal basins with relatively deep channels require relatively narrow flats to create zero asymmetry-induced sand transport, thus promoting dynamic equilibrium. By accepting these semi-empirical observations of dynamic equilibrium, an aggregated-scale model assesses the macroscale response of tidal basins and ebb-tidal deltas to natural and human forcing. Morphodynamic response of tidal basins consists of a complex mix of several time scales, which may differ in the order-of-magnitude.
The Yellow River in China is characterized by channel erosion and a meandering channel pattern at both low sediment concentrations and at hyperconcentrations, whereas deposition and braiding tends to dominate at intermediate sediment concentrations. A 3D numerical model (Delft3D) is used to analyze the effect of sediment-induced density effects on the formation of channel patterns using a highly simplified river geometry. Results show that the effect of vertical sediment density stratification and hindered settling significantly influence river channel patterns. At some critical concentration (the saturation concentration), vertical mixing is totally damped by the density gradients at the lutocline (a strong vertical gradient in sediment concentration). This increases the secondary circulation in the river channel significantly, which in turn promotes meander development. When the flow is not close to saturation, the main channel-forming process seems to be channel avulsion through blocking of old channels and subsequent channel cut-off. When the concentrations are so high that sediment is primarily held in suspension by hindered settling, sedimentation is so much reduced that channels are no longer blocked and therefore the river course becomes confined to a single meandering channel.
A successful project in Malawi designed to provide
a viable method of short-haul transport, in rural
areas with poor infrastructure, for agricultural
produce is described. The tractor plus two trailers
unit that was developed was not only efficient but
cost effective compared to other systems. It was
also assembled and therefore could be maintained
by skilled workers locally. The problems of raising
capital for projects of this kind are discussed.
Gallium nitride (GaN) epilayers with nanopore arrays were fabricated by inductive coupled plasma (ICP) etching using anodic aluminum oxide (AAO) as mask. Nanoporous AAO templates were formed by anodizing the Al films deposited on GaN epilayers. The diameter of the perforations in the AAO masks could be easily controlled by tuning the technique parameters of AAO fabrication process. Cl2/Ar and Cl2/He were employed as etching gas. Scanning electron microscopy (SEM) analysis shows that vertical nanoporous arrays with uniform distribution can directly be transferred from AAO masks to GaN films in some proper conditions. Photoluminescence (PL) spectra, X-ray diffraction (XRD) and Raman spectroscopy were applied to assess properties of the nanoporous GaN films with different average pore diameters and interpore distances.
Contents: River characteristics; Use of rivers; Water movement; Sediment transport; River morphology; Mapping; Water levels; Bed levels; Discharges; Stage/discharge relationship; Sediments; Water quality; Mathematical models; Scale models; Bed regulation; Discharge control; Water level cntrol; Water quality control; River engineering for various purposes.
Negative selection algorithms generate their detector sets based on the points of self data. In the approach described in this paper, the continuous self region is defined by the collection of self data. This has important differences from the negative selection algorithms that simply take each self point and its vicinity as the self region: when the training self points are used together as a whole, more information is provided than used as individual points; the boundary between self and nonself regions are detected in the algo-rithm. It also demonstrated that a negative selection algo-rithm as a unique strategy can obtain certain results that straightforward positive selection cannot. Experiments are carried out using both synthetic data and real world applica-tions. The former was designed to highlight the difference from conventional point-wise interpretation of self data in negative selection algorithms. KEY WORDS Artificial Immune Systems (AIS), Negative Selection Al-gorithms (NSA).
The fluvial and morphological processes induced by impoundment of the Sanmenxia Reservoir and relevant human activities on the Yellow River and its tributaries are complex. The long‐term annual sediment load of the Yellow River was 1.6 billion tons, ranking first of all the world's rivers. In 1960, Sanmenxia Dam began filling. Sediment transport in the river then was greatly disturbed and a new cycle of the fluvial processes was induced. First, the dam caused not only anticipated sedimentation in the reservoir, but also serious sedimentation in the largest tributary of the river (the Weihe River). The response of fluvial process to the dam closure varies in space and time. Second, the downstream reaches of the dam experienced erosion and resiltation, changes of river pattern, and development of meanders. Moreover, the downstream reaches of the dam have experienced more and more water diversion, which has induced readjustment of the longitudinal profile of the river. The study reveals that sedimentation in the Sanmenxia Reservoir enhanced the bed elevation at Tongguan, where the Weihe River flows into the Yellow River. The rising Tongguan's elevation caused retrogressive siltation waves in the Weihe River, which propagated at a speed of about 10 km/yr. An equilibrium sedimentation model is proposed, which agrees well with the data of sedimentation in the Weihe River. In the reaches below the dam the river changes from braided to wandering, or from wandering–braided to wandering–meandering. The discharge released to the downstream reaches has been regulated by the reservoir and it decreases along the course because the quantity of water diversions is more than the inflow from tributaries. The reduction in discharge causes readjustment of the longitudinal bed profile. By using the minimum stream power theory, we prove that the riverbed profile is developing toward an “S‐shape” profile.
The equilibrium condition in tidal basins, especially in the Dutch Wadden Sea, a multi-basin tidal system, has been the subject of numerous studies in recent decades. This concept is very important when the tidal basin imports sediments from the adjacent coastline and its ebb-tidal delta. In the Dutch Wadden Sea, the construction of the Afsluitdijk in 1932 has affected the behavior of tidal basins, especially the Marsdiep, to a large extent and disturbed its equilibrium condition. Today, 76 years after the construction of the Afsluitdijk, the Marsdiep has not reached a new equilibrium condition and it continues to import large volumes of sand every year.In this study a process-based model based on shallow water equations is used to simulate the morphological changes of the Western Wadden Sea for a duration of more than 2000 yr. The main forcing included in the simulations is tidal forcing and simulations with different initial conditions of the model are carried out.The main parameters of the Marsdiep tidal basin are calculated and compared with empirical equilibrium relations suggested in the literature. It is shown that such a process-based model can simulate the morphological evolution of tidal basins like the Marsdiep and can model a stable (equilibrium) condition in these basins. This stable condition is, however, strongly dependent on the initial conditions of the model as well as the forcing conditions. This paper also looks at the effect of different initial conditions on the channel and shoal pattern formation.In addition, some simulations are carried out with initial real bathymetry and the migration of the boundaries of tidal basins in the Western Dutch Wadden Sea is analyzed. The hypothesis that the basins are expanding towards the east, especially in the case of the Marsdiep, is also tested in these simulations.
This study focuses on the prediction of the long-term morphological evolution of tidal basins due to human interventions. New analytical results have been derived for an existing model [ASMITA, Aggregated Scale Morphological Interaction between a Tidal inlet and the Adjacent coast; Stive, M.J.F., Capobianco, M., Wang, Z.B., Ruol, P., Buijsman, M.C., 1998. Morphodynamics of a Tidal Lagoon and adjacent Coast. 8th International Biennial Conference on Physics of Estuaries and Coastal Seas, The Hague, September 1996, 397–407.]. Through linearisation of the model equations a set of time scales is obtained that describe the main features of the morphological evolution of tidal inlets. The magnitude of these system time scales is determined by inlet geometry and sediment exchange processes. The nature and degree of interventions determine which time scales are dominant. We focus on five different tidal inlets in the Wadden Sea. For these inlets, the system time scales have been estimated. The model has been applied to simulate the morphological response of the Marsdiep and Vlie inlets to the closure of the Zuiderzee in 1932. In this way, the model and associated system time scales for each of these inlets have been validated. Results show that in both inlets, the channels display the largest adaptation time. It will take at least a century before the channels and hence the tidal inlet systems reach a new morphological equilibrium.
Channel shrinkage and its instability in the Lower Yellow River
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Chen Jianguo, Zhou Wenhao, and Deng Anjun. 2006, Channel shrinkage and its instability in the Lower Yellow
River. International Journal of Sediment Research, Vol. 21, No. 1, pp.13-23.
Interactions between fluvial systems and large-scale hydro-projects A study on the effect of Tongguan's elevation on sedimentation in the Weihe River
- Hu Chunhong
Wang Zhao-Yin and Hu Chunhong. 2004, Interactions between fluvial systems and large-scale hydro-projects. Keynote lecture at 9 th International Symposium on River Sedimentation, October, Yichang China. Wang Zhao-Yin and Li Changzhi. 2003, A study on the effect of Tongguan's elevation on sedimentation in the Weihe River. Research Report, Institute of River and Coastal Engineering, Tsinghua University (in Chinese).
Morphological interaction between the Yellow River and its estuary Regulation of flow and sediment load in the Yellow River
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Analysis of the instable Yellow River channel size decrease
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the Institute of Water Resources and Hydropower Research, Vol. 3, pp. 291-296.
Analysis on fluvial processes and failure of spur dykes in the Lower Yellow River
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Wang Zhao-Yin, Cheng Dongsheng, Li Changzhi, and Zhou Jing. 2004, Analysis on fluvial processes and failure of
spur dykes in the Lower Yellow River. Research Report, Institute of River and Coastal Engineering, Tsinghua
University (in Chinese).
Impact of sea level rise on the morphology of the Wadden Sea in the scope of its ecological function. ISOS*2 Project
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Project, phase 1, Report H1300, WL | Delft Hydraulics, Delft.
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barrier islands, ebb-tidal deltas, inlets and drainage basins, Doctoral thesis, Utrecht University.
Development and application of a large-scale morphological model of the Dutch coast, Phase 2: Formulation and application of the PONTOS
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Formulation and application of the PONTOS model 1.4, Report Z3334, WL | Delft Hydraulics.
Morphological development of the Rif and the Engelsmanplaat, an intertidal flat complex in The Frisian Inlet, Dutch Wadden Sea
- Z B Wang
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Frisian Inlet, Dutch Wadden Sea, Proceedings of 32nd Conference on Coastal Engineering, Shanghai, China, 2010. Paper #:
sediment.54. Retrieved from http://journals.tdl.org/ICCE/.
Morphodynamics of the Wadden Sea and its Barrier Island System
- Z B Wang
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Sea and its Barrier Island System, Ocean and Coastal Management, 68, pp. 39-57, doi:10.1016/j.ocecoaman.2011.12.022.
Principles of River engineering: the non-tidal alluvial river
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Modelling of flood defence measures in the Lower Yellow River using SOBEK. International Yellow River Forum (IYRF) on River Basin Management
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Yellow River using SOBEK. International Yellow River Forum (IYRF) on River Basin Management, Zhengzhou,
China, October, pp. 21-24.
Morphological interaction between the Yellow River and its estuary
- Kriele
Kriele H. O., de Vries M., and Wang Z. B. 1998, Morphological interaction between the Yellow River and its estuary,
in Dronkers, J. and Scheffers, M., (eds.). Physics of Estuaries and Coastal Seas, A.A.BALKEMA, Rotterdam.
A study on the effect of Tongguan's elevation on sedimentation in the Weihe River
- Wang Zhao-Yin
- Li Changzhi
Wang Zhao-Yin and Li Changzhi. 2003, A study on the effect of Tongguan's elevation on sedimentation in the
Weihe River. Research Report, Institute of River and Coastal Engineering, Tsinghua University (in Chinese).
Fluid-sediment interaction in silt-laden flow. International Yellow River Forum (IYRF) on River Basin Management
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Winterwerp Johan C., de Vriend Huib J., and Wang Zhengbing. 2003, Fluid-sediment interaction in silt-laden flow.
International Yellow River Forum (IYRF) on River Basin Management, Zhengzhou, China, October 21-24.
Development of meanders under varying water and sediment load conditions in the Lower Yellow River
- Zhou Jing
- Wang Zhao-Yin
- Li Changzhi
- Liu Ji-Xiang
Zhou Jing, Wang Zhao-yin, Li Changzhi, and Liu Ji-xiang. 2006, Development of meanders under varying water and
sediment load conditions in the Lower Yellow River. Journal of Sediment Research, No. 1, pp. 45-50 (in Chinese).
Analysis of the instable Yellow River channel size decrease
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Yellow River basin management and current issues
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Channel shrinkage and its instability in the Lower Yellow River
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Development of meanders under varying water and sediment load conditions in the Lower Yellow River
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