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The Gezhouba Reservoir (GR) and Three Gorges Reservoir (TGR) are the two largest water-storage projects in the middle reach of the Yangtze River. The impoundments of the reservoirs have changed natural flow-regimes in the river. This paper uses the Yichang Hydrological Station as a proxy for water-storage projects along the Yangtze River to assess alterations in river-flow conditions in three separate periods. The periods coincide with the start of water storage in the GR and TGR. The ecohydrological conditions in the river system are assessed based on annual discharge, water level, water temperature, and suspended-sediment concentration. More importantly, the entire analysis is done in relation to the Chinese sturgeon species, which face the danger of extinction in the Yangtze River. Based on the research reported in this paper, the impoundment of the GR and TGR increases downstream average annual water-temperature. In contrast, it decreases downstream average annual runoff, water level, and suspended-sediment concentration. The change of hydrological conditions negatively influences the spawning and hatching conditions of Chinese sturgeon. This change is the key reason that causes the fertilized rate of Chinese sturgeon eggs to decline. [ABSTRACT FROM AUTHOR]

Accurate and reliable prediction of runoff generation is necessary for flood control scheduling, water supply planning, and hydropower generation. Support vector machine (SVM), which is at the forefront of current research of regression and classification, was used in this paper to conduct monthly mean streamflow prediction. A novel heuristic optimization named bat algorithm (BA) was introduced to determine the parameters of SVM [penalty parameter (C) and kernel parameter (η)], in which the initial fitness was supposed to be equal to the initial loudness for all bats. In order to evaluate the effectiveness of the proposed approach, monthly mean streamflow from 1952 to 2011 of Yichang station in the middle reaches of the Yangtze River were trained and tested. In the meantime, the given data set was also modeled using artificial neural networks (ANN) and cross validation-based SVM. The comparison results indicate that the proposed model (bat algorithm-based SVM) is more accurate compared with both ANN and cross validation-based SVM. However, two main shortages exist, i.e., time-consuming and relatively low accuracy in the break points of continued dry (wet) years. To relieve these shortages, local optimization algorithms [e.g., differential evolution (DE) algorithm, immune algorithm (IA), and genetic algorithm (GA)] were suggested to be combined with the bat algorithm to produce the initial population. Modifications of the stochastic term of the local search were also useful. [ABSTRACT FROM AUTHOR]

U-section steel sheet piles are widely used as support structures in bridge foundation pit excavation. Because of the reduced modulus action (RMA) effect of U-section steel sheet piles, it is difficult to balance structural safety and construction cost in engineering. In this paper, a case study of a foundation pit supported by U-section steel sheet piles in the middle and lower reaches of the Yangtze River was carried out. A three-dimensional FEM of the support structure was established and the RMA parameter analysis was conducted. According to the measured data, the RMA value was identified. Based on the RMA value, the support structure of the subsequent foundation pit was optimized and the deformation of the pile head was monitored during the excavation process. The measured deformation was in good agreement with the predicted value, verifying the feasibility of the inferred RMA value. Finally, to solve the uncertainty problem of the U-section steel sheet pile RMA in general situations, an optimization strategy for the design of the U-section steel sheet pile support structure was proposed. [ABSTRACT FROM AUTHOR]

Recently, increasing nutrient (i.e., nitrogen and phosphorus) concentrations have been observed in the surface water of many countries and this nonpoint source (NPS) pollution has become an important factor in the deterioration of water quality in the upper reach of the Yangtze River Basin. In this paper, the NPS pollution loads in the upper reach of Yangtze River Basin in the year 2000 were estimated using export coefficient model and remote sensing techniques. The spatial distributions of the NPS loads within the watershed were then displayed using geographical information system. Results indicated that the total nitrogen load was 1.947×106 t and the total phosphorus load was 8.364×104 t. Important source areas for the nutrients were croplands in the Jinsha R. and Jialing R. watershed, as well as the Chongqing municipality. [ABSTRACT FROM AUTHOR]

This paper describes a record setting project in the horizontal directional drilling field involving twin pipes with a diameter of 711 mm and a length of 3,300 m. The Yangtze River is the longest river in China. The Jiangdu-Rudong gas pipeline, which is part of the Chinese gas pipeline trunk network, was constructed to transport gas from the north side to the south side of the River. The width of the river surface is 3,000 m, and the length of the crossing is 3,300 m. It was recommended by engineers that twin pipes with a diameter of 711 mm be used instead of the existing pipe with a diameter of 1,016 mm. The required depth of penetration for the crossing was determined by an analysis of 43 years of historical river scour data from 1966 to 2009 combined with a calculated result using a river scour depth formula. The recommended construction scheme included arranging two drilling rigs, laying magnetic-signal submarine cable, using the intersect method, and designing a new flat-barrel combination-type reamer. This major project was finished successfully on July 27, 2013. [ABSTRACT FROM AUTHOR]

With the advent of acoustic Doppler current profiler (ADCP), the velocity profile method or index velocity method based on a single profile or a fixed-depth cell has been recommended for estimating discharge in tidal reaches. However, in large tidal reaches with a width of nearly 6 km and cross-sectional variability of flow, such as Yangtze Estuary, these methods are not accurate enough for the discharge estimation. Therefore, an improved method named the multiprofile method, is proposed in this paper. The method includes four main steps: (1) calculating the cross-sectional area A with stage data by considering the transverse slope; (2) calculating the depth-mean velocity u at each fixed ADCP; (3) establishing the u − U model with the multiprofile us and estimating the cross-sectional mean velocity U; (4) estimating the final discharge through U multiplied by A. The proposed method was tested at the Xuliujing section of the Yangtze Estuary. The result shows that the multiprofile method averagely improves the accuracy by approximately 5.8% relative to the single-profile method in the discharge estimation, which proves the proposed method to be valid in the discharge estimation of large tidal reach. [ABSTRACT FROM AUTHOR]

The flow regime of the Yangtze River (Changjiang) has been altered to some extent by intensified human activities over the past decades, particularly dam construction. To assess the impacts of dam building on the flow regime in the Yangtze River, two of the largest reservoirs on the upper reach, i.e., the Gezhouba and Three Gorges reservoirs, have been selected as case study sites. To analyze the changes in flow regime between predam and postdam periods, the whole study period was divided into three subperiods according to the years when these two reservoirs started to store water. On the basis of the time series of daily flow discharge from four key hydrological stations, i.e., Cuntan, Yichang, Hankou, and Datong, the alterations in annual, seasonal, monthly, and daily flow regimes and water rising or falling regime in different subperiods were investigated and the driving forces were explored. The results revealed the impacts of the two reservoirs on their downstream flow regime varied with reservoir storage capacity and the distance between the target reservoir and the case study site, the Gezhouba and Three Gorges reservoirs imposed various impacts on different time scales of downstream runoff regime, and the operation of these two reservoirs altered the water rising and falling regime to some degree, which is particularly critical for the spawning of Chinese sturgeon and the four major domestic carp. The output of the paper could provide references for the assessment of impacts of dam construction on the health and stability of the Yangtze River ecosystem. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A new static-based method for damage detection of cable-stayed bridges using the changes in cable forces is presented in this paper. In recognizing the fact that damage incurring in bridge girders will cause a redistribution of forces in stay cables, the proposed method uses the measured changes in cable forces to detect the damage in bridge girders. In this method, the damage identification is formulated as an optimization problem in which the cable force error between measurement results and analytical model predictions is minimized. The sensitivities of cable forces with respect to the structural parameters of bridge girders for the linear and geometrically nonlinear bridge structures are obtained by using the direct differentiation method and the finite difference method, respectively, and are used to solve the optimization problem. Regularization technique is used to alleviate ill-conditioning in the solution course of the optimization problem. The validity of the method is illustrated by numerical studies of damage detection of the cable-stayed Sutong Bridge with a main span of 1,088 m. The effect of measurement noises and the number of measured cable forces on the accuracy of damage quantification is investigated. The proposed method correctly identifies the damage locations and damage magnitudes in bridge girders when using noise-free cable forces. It is also shown that structural damage can be quantified with acceptable accuracy in the case of low-level measurement noises and the damaged members being well spaced, and the identification accuracy is greatly improved when the forces in the cables connected to the damaged members are available for damage quantification. [ABSTRACT FROM AUTHOR]

In a flood-prone region, quick and accurate flood forecasting is imperative. It can extend the lead time for issuing disaster warnings and allow sufficient time for habitants in hazardous areas to take appropriate action, such as evacuation. In this paper, two hybrid models based on recent artificial intelligence technology, namely, the genetic algorithm-based artificial neural network (ANN-GA) and the adaptive-network-based fuzzy inference system (ANFIS), are employed for flood forecasting in a channel reach of the Yangtze River in China. An empirical linear regression model is used as the benchmark for comparison of their performances. Water levels at a downstream station, Han-Kou, are forecasted by using known water levels at the upstream station, Luo-Shan. When cautious treatment is made to avoid overfitting, both hybrid algorithms produce better accuracy in performance than the linear regression model. The ANFIS model is found to be optimal, but it entails a large number of parameters. The performance of the ANN-GA model is also good, yet it requires longer computation time and additional modeling parameters. [ABSTRACT FROM AUTHOR]

Flow complexity, which means the degree of uncertainty or the rate of information production of a flow series, is analyzed for the upper reaches of the Yangtze River. Sample entropy (SampEn) is applied to measure flow complexity, and the Mann-Kendall method is applied to analyze the trend of flow-complexity change. Except for the flow complexity of the Jinsha River, which is increasing, the flow complexity of the upper reaches of the Yangtze River is decreasing. The influencing factor of the flow-complexity change is analyzed. On the basis of analysis of the rainfall complexity, which is also measured by SampEn, it is considered that the flow-complexity increase of the Jinsha River may be attributed to the rainfall-complexity increase, while the flow-complexity loss of the upper reaches of the Yangtze River may be attributed to the underlying surface-condition change influenced by human activities, especially reservoir construction. The reservoir operation makes the flow series more regular and self-similar, and leads to the flow-complexity loss. [ABSTRACT FROM AUTHOR]

Temperature field data from the steel truss arch girder and longitudinal displacement data from six groups of rubber bearings were collected by the structural health monitoring system for the Dashengguan Yangtze Bridge. By using long-term monitoring data, two correlations are investigated: the linear correlation between the longitudinal displacement and the temperature field (including uniform temperature and temperature gradient); and the linear correlation of the longitudinal displacements in different locations. A multivariate linear regression equation is used to model the first correlation, and a Lagrange polynomial interpolation is used to model the second correlation. The final mathematical models, representing the healthy state of the bearings, can be applied to simulate the longitudinal displacements of the main girder. Furthermore, the change regularity of longitudinal displacements for the degraded rubber bearings is revealed taking advantage of a hysteretic model and presumed envelope curves of frictions caused by bearing degradation. A method of detection and location for the degraded bearings is proposed in four detailed steps, and the numerical results demonstrate that this method is effective. [ABSTRACT FROM AUTHOR]

Two river crossing cases are considered in which a pipe is installed beneath the Yangtze River using horizontal directional drilling (HDD). In both cases, a length of pipeline located on the rock strata near the north bank, including a local protrusion, is disrupted by river erosion. A three-dimensional (3D) model is developed to simulate the river erosion based on the finite-element software ABAQUS, which is capable of modeling the properties of the soil and pipelines, as well as their interaction. Results are presented based on an analysis of the stress concentration points at the ends of the rock protrusion, in the vicinity of the erosion. The effect on the pipelines is investigated as a function of the depth, extent, and location of the erosion. The resulting stress and displacement along the crown, spring, and invert lines of the pipelines are shown and compared to the function of the depth, extent, and location. And the stress concentration points occur at the location of rock protrusion and in the vicinity of the eroded soil. [ABSTRACT FROM AUTHOR]

A hybrid rainfall-runoff model that integrates artificial neural networks (ANNs) with Xinanjiang (XAJ) model was proposed in this study. The writers extracted the digital drainage network and subcatchments from digital elevation model (DEM) data considering the spatial distribution of rain-gauge stations. Then the semidistributed XAJ model was established based on DEM. Considering the runoff routing cannot be calculated by the linear superposition of the route runoff from all subcatchments, artificial neural networks as effective tools in nonlinear mapping are employed to explore nonlinear transformations of the runoff generated from the individual subcatchments into the total runoff at the entire watershed outlet. The integrated approach has been demonstrated as feasible and was applied successfully in the Yanduhe watershed, the upper tributary of Yangtze River Basin. The results indicated that the approach of integrating back-propagation ANN with semidistributed XAJ model may achieve the promising results with acceptable accuracy for flood events simulation and forecast. [ABSTRACT FROM AUTHOR]

The coincidence of flood flows of the mainstream and its tributaries may determine flood peaks. This study analyzed the risk of flooding as a result of such flood coincidences by considering flood magnitudes and time (dates) of occurrence. The Pearson Type III (P3) and log-Pearson Type III (LP3) distributions were selected as the marginal distribution of flood magnitude for annual maximum flood series; the mixed von Mises distribution was selected as the marginal distribution of flood occurrence dates. Two four-dimensional (4D) copula functions were developed for the joint distribution of flood magnitudes and occurrence dates. The upper Yangtze River in China and the Colorado River in the United States were selected to evaluate the method of computing risk. The coincidence probabilities of flood magnitudes and dates were calculated, and the conditional probabilities for the Three Gorges Reservoir (TGR) were analyzed. Results show that the von Mises distribution can fit the observed flood dates data well. The X-Gumbel copula was selected for risk analysis. On the basis of the proposed model, the coincidence and conditional probabilities for any return period were obtained. [ABSTRACT FROM AUTHOR]

The Yangtze River delta urban agglomeration of China has experienced a significant development bloom in the last 30 years. To explore the spatial structure, a series of methods have been applied in this study: a mathematical analysis to ascertain the framework of cities in this urban agglomeration, a research on the expansion of completed areas, and population density on the basis of the grid analysis. It has been identified that a single-nucleus and several-centers model could be the best model to suit the spatial structure. This model, similar in many classical cases of spatial-structure model of conurbations and urban agglomerations, can be utilized to speed up urbanization, provide reasonable modes to industry spreading, establish special functional cores, and protect the environment in both urban and rural regions. [ABSTRACT FROM AUTHOR]

This study investigated the traffic-induced stresses in the steel deck of a suspension bridge on the Yangtze River, taking into account the dependence of Young's modulus of asphalt pavement on temperature. In particular, the stress spectra of local areas in the steel deck were studied. On the basis of the massive traffic data collected by a bridge toll system over one month, traffic composition and the vehicle load were statistically analyzed, and then a random traffic flow model that reflected the statistical characteristics of actual traffic flow, was generated. Through a bridge dynamic analysis of the random traffic flow model, a segment of the steel box girder which experiences the greatest stress was selected. The local stress variation and the stress spectrum under traffic flow were analyzed using a finite-element model (FEM). In the FEM analysis process, the impact of the temperature on mechanical properties of the asphalt pavement was considered. The results show that the middle segment of the main span has the largest moment amplitude. In addition, it was observed that the variation of Young's modulus of asphalt pavement resulting from temperature change can significantly affect the stress of the steel box girder and the stress spectrum at different local areas in steel deck. [ABSTRACT FROM AUTHOR]

At the South Branch of the Changjiang Estuary near Baimao Shoal, two in situ approaches were used to estimate the settling velocity, ws, of suspended, fine-grained sediments. The first approach was used when the current was less than 1.5 m/s and was based on measurements from an optical backscatter sensor (OBS-3A) and a laser in situ scattering and transmissometer (LISST-100, Type C). A modification, using the measured ratio of volume concentration for each floc size class to the total volume concentration as a weighting factor. To improve a previously published approach, a better algorthim was implemented to estimate ws. Results of the modified approach (0.4 to 4.6 mm/s) are about twice those of the original approach, which assumes that all sizes of flocs have the same floc density. The second approach used the Rouse equation to estimate the depth-averaged ws when the current was strong and nearly steady around maximum ebb. Results from the second approach show a much greater depth-averaged ws (4-8.5 mm/s). This is attributed to the large bed shear stresses (between 3 and 3.6 Pa) bringing large sediments into the water column. [ABSTRACT FROM AUTHOR]

With an increasing tendency of the flood disaster frequency and intensity in China, risk analysis of design flood volume for the Three Gorges Dam Project (TGP) should be of paramount importance for about one-half of the population and gross domestic product in China. How to predict the floods of Yangtze River with high precision is always a difficult problem, for the vast drainage basin and numerous tributaries. After a brief introduction of extreme value distribution and compound extreme value distribution, the TGP design flood volume predicted by the Chinese Hydraulic Design Code (CHDC) recommended annual maximum data sampling based Pearson type III extrapolation method is compared with the stochastic simulation technique based on the important sampling procedure (ISP) and the multivariate compound extreme value distribution (MCEVD), respectively. Comparison results show that the 100-year joint return period of the 3-day flood volume predicted by ISP and MCEVD is greater than 1,000-year return volume predicted by CHDC recommended method. [ABSTRACT FROM AUTHOR]

The effects of the sediment regime on the flood level in the middle reach of the Yangtze River before and after the construction of the Three Gorges Dam (TGD) are investigated. Before the dam construction, the sediment regime has driven the flood level higher and higher over recent decades in the middle reach of the Yangtze River, which has reflected changes in the location and amount of sediment deposition. After dam completion, the magnitude and rate of channel degradation determines the process of flood stage lowering but they are difficult to estimate owing to insufficient understanding of the sediment discharge recovery process. To make a rational prediction of channel degradation of the Yangtze River downstream from the TGD, the sediment transport rate during channel degradation downstream from other dams is examined. It is found that, for any grain size, postdam sediment transport rates cannot exceed the predam level at any location along the downstream channel. Erosion amounts predicted for the reach downstream from the TGD before its closure are too high. In light of this, a numerical simulation of the channel degradation process is carried out. The results indicate that, although degradation takes place immediately after the TGD closure, the flood level in the middle reach of the Yangtze River will still remain at its predam condition in the following 20 years. This is determined not only by the regional characteristics of the middle reach of the Yangtze River but also by the common law of sediment transportation downstream from dams. [ABSTRACT FROM AUTHOR]

The TR2004 transport formulations for clay, silt, and sand as proposed in Parts 1 and 2 have been implemented in morphodynamic models to predict bed level changes. These models have been verified using various laboratory and field data cases concerning coastal flow in offshore and near-shore zones. Furthermore, the model has been applied to two complicated sediment environments concerning the flow around a spurdike in a river and the tidal flow of cohesive sediments in the Yangtze Estuary in China. Overall, it is concluded that the morphodynamic models using default settings performs reasonably well. The applied scaling factors of the sediment transport model are in the generally accepted range of 0.5–2. [ABSTRACT FROM AUTHOR]

To evaluate the performance of a computer model simulating runoff and sediment load in the upper region of the Changjiang (Yangtze River) basin over a relatively short time interval, including examining the applicability of the input precipitation data generated from global circulation models and satellite data, we used a spatially distributed model, HSPF with the International Satellite Land Surface Climatology Project (ISLSCP) precipitation data for 1987 and 1988 as input data. The Nash–Sutcliffe coefficient (R2) for 5-day average streamflow was 0.94 in the calibration period and 0.95 in the verification period for the whole upper region. Moreover, the model simulated the 5-day average streamflow well in each main tributary, as shown by R2 values of 0.46–0.96, except that it underestimated the peak flow rates during the flood season over 2 years by up to 71% in Tuojiang and 61% in Jialingjiang. The model simulated the 5-day concentrations of suspended solids (SS) fairly well in the headwaters and upper regions of the Jinshajiang, Yalongjiang, and Minjiang watersheds, as shown by R2 values of 0.31–0.65. In the other regions, however, the model underestimated the SS load by up to 72%, and rarely simulated the fluctuation of SS concentration in each river channel during the flood season. These errors led to the underestimation of sediment runoff volume from the whole upper region during the flood season, as shown by the ratio of the simulated sediment load to the observed data at Yichang: 0.69 in the calibration period and 0.68 in the verification period. The ISLSCP precipitation tended to be more frequent and less intense than the measured precipitation. This was probably the main reason why the HSPF did not perform well in all regions at all times. [ABSTRACT FROM AUTHOR]

Artificial neural networks (ANNs) have proved to be an efficient alternative to traditional methods for hydrological modeling. One of the most important steps in the ANN development is the determination of significant input variables. This study proposes a new method based on the copula-entropy (CE) theory to identify the inputs of an ANN model. The CE theory permits to calculate mutual information (MI) and partial mutual information (PMI), which characterizes the dependence between potential model input and output variables directly instead of calculating the marginal and joint probability distributions. Two tests were carried out for verifying the accuracy and performance of the CE method. The CE theory-based input determination methodology was applied to identify suitable inputs for a flood forecasting model for a real-world case study involving the three gorges reservoir (TGR) in China. Test results of application of the flood forecasting model to the upper Yangtze River indicates that the proposed method appropriately identifies inputs for the ANN with the smallest root-mean-square error (RMSE) for training, testing, and validation data. [ABSTRACT FROM AUTHOR]