The results from both the field measurements and numerical simulation were reported to comprehensively analyze the sediment siltation in the upper reach of the Deepwater Navigation Channel Project in the Yangtze Estua...The results from both the field measurements and numerical simulation were reported to comprehensively analyze the sediment siltation in the upper reach of the Deepwater Navigation Channel Project in the Yangtze Estuary after the project has been implemented. In this research, firstly some basic information about the river evolution in the Yangtze Estuary is analyzed, including the variations of water depths in the Hengsha Passage and the inlet cross-sections of the North Passage and the South Passage, and changes of diversion ratios of ebb flow and sediment flux in the North Passage and the South Passage, Then the Delfl3D-FLOW model is applied to simulate the hydrodynamics and sediment transport in the Yangtze Estuary. This model has been calibrated and the simulated results agree well with the measured data of the tidal levels, flow velocities and suspended sediment concentration （SSC）, indicating that the model can well simulate the hydrodynamics and sediment transport of the Yangtze Estuary caused by the Deepwater Navigation Channel Project. The research results show that the development of the Hengsha Passage and decrease of diversion ratio of ebb flow and sediment flux in the North Passage are the main reasons of sediment siltation in the upper reach of the Deepwater Navigation Channel in the Yangtze Estuary.展开更多
The Three Gorges Project(TGP)has changed the flow-sediment process in the middle Yangtze River.For navigation purposes,there is an urgent need to study the changes of the river regime over a long-term period and the s...The Three Gorges Project(TGP)has changed the flow-sediment process in the middle Yangtze River.For navigation purposes,there is an urgent need to study the changes of the river regime over a long-term period and the shoal-channel evolution over different seasons since the completion of the TGP.Based on analysis of the measured data and the results of a two-dimensional mathematical model,the changes of the river regime and river bed evolution in the Yaojian reach downstream of the TGP were studied.Results show that a high sediment transport flux helps to keep the main flow in the North Branch,while a low sediment transport flux helps to keep the main flow in the South Branch.Thus,the main branch will not change in the near future because of the low sediment transport load.In this study,the flow-sediment process adjusted by the TGP was restored to the conditions before the TGP,and the river bed evolution under the adjusted and non-adjusted flow-sediment conditions was calculated.After the completion of the TGP,the reservoir storage accelerated the flood recession process and decreased the erosion by 11.9%under the flow-sediment conditions in 2010,and the deposition in the flood season decreased by 56.4%.展开更多
Sediment research of TGP has been carried out for more than 40 years since 1958.This paper briefly describes the sediment research work of Yangtze River Scientific Research Institute in the reservoir area and damsite ...Sediment research of TGP has been carried out for more than 40 years since 1958.This paper briefly describes the sediment research work of Yangtze River Scientific Research Institute in the reservoir area and damsite area of TGP in recent years.The research results demonstrate that sediment from Jinsha river and Jialing river reaches 83% of the total sediment at TGP.The completion of Xiluodu,Xiangjiaba and Tingzikou reservoirs will postpone the initial sediment balance time in TGP reservoir. In initial operation period of the project,the sediment in approach channels of the navigation structures can be cleared by machinery,in future period,the sediment outside the entrances of the upper and lower approach channels still need to be cleared by machinery while the sediment within the approach channel should be cleared by joint measures of flushing and mechanical dredging.展开更多
The Dinh An Estuary is one of the Nine Dragon estuaries of the Mekong River. An international navigation channel was built in the estuary for vessels traveling from the South China Sea to the southwestern area of Viet...The Dinh An Estuary is one of the Nine Dragon estuaries of the Mekong River. An international navigation channel was built in the estuary for vessels traveling from the South China Sea to the southwestern area of Vietnam and then to Phnom Penh, Cambodia. The morphological evolution of the navigation channel is complicated and unstable. The back siltation intensity in the navigation channel has largely increased and been concentrated in the curvature segments of the channel since 1980. In this study, based on simulation results and measured data, five key factors that influence the back siltation in the navigation channel were systematically analyzed. These factors included the increasing elevation gap between the channel and the nearby seabed, the disadvantageous hydrodynamic conditions, sediment transport, mixing of saltwater and freshwater, and wave effects in the navigation channel. It is shown that the back siltation to a large extent results from the low current velocity of the secondary ocean circulation, which often occurs in the curvature segments of the channel. Suspended sediment also settles in the channel due to the decrease of the current velocity and the sediment transport capacity when flow passes through the channel. The changes of hydrodynamic conditions are responsible for the majority of the severe siltation in the curvature segments of the navigation channel.展开更多
Based on field investigations, this paper analyzes three types of harbour basinns and navigation channel excavated on seabed in Jiaozhou Bay, get a general rule of deposition for excavated trough, it found that pollut...Based on field investigations, this paper analyzes three types of harbour basinns and navigation channel excavated on seabed in Jiaozhou Bay, get a general rule of deposition for excavated trough, it found that pollution is one of crucial factors resulting in the deposition of the excavated trough in the east shore of Jiaozhou Bay. With these results, it predicted the annual deposition thickness for the excavated trough and disclosed the fact that it can't be deposited deadly during one storm. At the same time, with two-dimensional numerical model, it studied the effects of the excavated trough and the reclamation near shore on tidal cureent and said that the excavated trough can decrease the current velocity passing through the trough about 10- 15%, but only limited inside and near the trough and there are no effect on other regions; reclamation can cut off the pollution sources and no obvious effect on the currents of the Jiaozhou Bay. Connecting the deep trough and Cangkou tidal channel with a new excavated trough can improve the current conditions on the deep trough in some degree, but not great.展开更多
This paper, after briefly reviewing the experimental research on sediment transport on muddy beach since the 1950s, improves and perfects the method for forecasting siltation in navigation channels and harbour basins ...This paper, after briefly reviewing the experimental research on sediment transport on muddy beach since the 1950s, improves and perfects the method for forecasting siltation in navigation channels and harbour basins which was first put forward in China by the authors. In consideration of silty sediment and sand, some factors in forecasting methods have been changed and modified. Consequently, the modified methods can be used either to compute siltation in navigation channels and harbour basins on muddy beach or to compute siltation and scouring in navigation channels and harbour basins on both silty beach and sandy beach. The verification of field data from eleven large, medium and small natural harbours shows a good agreement between the forecasting by the modified method and the natural conditions. Finally, the paper deals with the rational utilization of water area after the construction of the West Dyke in Lianyungang, the maintenance of water depth of the navigation channel at the entrance, siltation distribution, siltation in the navigation channel and harbour basin for ships of 100 thousand tonnnage. Results once again prove that the prospect of constructing Lianyungang Harbour into a deepwater harbour is bright.展开更多
Liquefied Natural Gas (LNG) port is located at Abu Qir Bay on the northwestern coast of the Nile delta, Egypt. The port was constructed in 2004 to export liquefied natural gas worldwide. The offshore basins of this po...Liquefied Natural Gas (LNG) port is located at Abu Qir Bay on the northwestern coast of the Nile delta, Egypt. The port was constructed in 2004 to export liquefied natural gas worldwide. The offshore basins of this port including the turning and berthing areas (15-m depth) are connected to the deep water by a 15-m depth dredged channel that extends 4 km offshore. However, the navigation channel and its contiguous basins have experienced problematic shoaling that might affect the navigation activities of gas tankers. Sedimentation processes have been investigated by analyses of waves, currents, bathymetry, grain size of seabed and channel dimensions. Sedimentation rates are estimated using a developed numerical model. Sedimentation rate fluctuates between 0.048 × 106 m3/month and 0.388 × 106 m3/month, with an annual sedimentation rate of 1.977 × 106 m3/yr. The variance in the sedimentation rates between winter and summer resulted in increasing of current speed and direction flowing towards offshore. The sedimentation process is influenced by the temporal variability in the direction and intensity of the predominant waves, currents, orientation of navigation channel, basin breakwaters, seafloor morphology and sediment sources. Due to the geographic location of LNG port it lays within a sediment sink for sediments supplied from different alternating directions by several pathways, flowing towards the N-W, S-W, N-E, and S-E quadrants. Most of these currents components are substantially effective in transporting fine-grained sediment towards the navigation channel axis and contiguous basins. Together with these currents, the predominant NW and SE waves acting to agitate and stirrup sediments in the vicinity of the port, and thereby accelerating sedimentation rates.展开更多
The morphological evolution characteristics of the North-South Passage area since the construction of the Yangtze Estuary Deepwater Navigation Channel Project(DNCP)are analyzed on the basis of the measured data.A twod...The morphological evolution characteristics of the North-South Passage area since the construction of the Yangtze Estuary Deepwater Navigation Channel Project(DNCP)are analyzed on the basis of the measured data.A twodimensional morphodynamics numerical model of the Yangtze Estuary is established to verify the morphological evolution of the North-South Passage under the influence of the DNCP and to predict the future evolution in the next 40 years.Data analysis shows that the North Passage has experienced rapid adjustment stages and adaptive stages after the construction of the DNCP.Slow erosion occurred along the main channel,and slow siltation could be observed in the area between the groins.The South Passage showed a state of upper section erosion and down section deposition.At present,the whole South Passage is in a slight erosion state.According to the numerical model,the eroding and silting speed of the North Passage will slow down in the future.The present state that erosion occurs in the main channel and siltation occurs between the groins will continue.The South Passage will still maintain upper section erosion and down section deposition in the future.Due to the main channel erosion of the North Passage and siltation of the South Passage,the sediment division ratio of the North Passage will increase in the future but still be smaller than 50%.After morphological evolution of 40 years,the direction of residual sediment transport caused by M2 and M4 tidal components in the North Passage has not changed,but the transport rate will decrease.It is considered that the morphological evolution of the North-South Passage could reach a relatively stable state after 40 years.展开更多
基金supported by the Key Subject Foundation of Shanghai Education Committee(Grant No.J50702)the Na-tional Key Basic Research Development Program of China(973 Program,Grant No.2012CB957704)
文摘The results from both the field measurements and numerical simulation were reported to comprehensively analyze the sediment siltation in the upper reach of the Deepwater Navigation Channel Project in the Yangtze Estuary after the project has been implemented. In this research, firstly some basic information about the river evolution in the Yangtze Estuary is analyzed, including the variations of water depths in the Hengsha Passage and the inlet cross-sections of the North Passage and the South Passage, and changes of diversion ratios of ebb flow and sediment flux in the North Passage and the South Passage, Then the Delfl3D-FLOW model is applied to simulate the hydrodynamics and sediment transport in the Yangtze Estuary. This model has been calibrated and the simulated results agree well with the measured data of the tidal levels, flow velocities and suspended sediment concentration （SSC）, indicating that the model can well simulate the hydrodynamics and sediment transport of the Yangtze Estuary caused by the Deepwater Navigation Channel Project. The research results show that the development of the Hengsha Passage and decrease of diversion ratio of ebb flow and sediment flux in the North Passage are the main reasons of sediment siltation in the upper reach of the Deepwater Navigation Channel in the Yangtze Estuary.
基金supported by the National Key Research and Development Program of China(Grants No.2016YFC0402307 and 2016YFC0402103)the National Natural Science Foundation of China(Grant No.51520105014).
文摘The Three Gorges Project(TGP)has changed the flow-sediment process in the middle Yangtze River.For navigation purposes,there is an urgent need to study the changes of the river regime over a long-term period and the shoal-channel evolution over different seasons since the completion of the TGP.Based on analysis of the measured data and the results of a two-dimensional mathematical model,the changes of the river regime and river bed evolution in the Yaojian reach downstream of the TGP were studied.Results show that a high sediment transport flux helps to keep the main flow in the North Branch,while a low sediment transport flux helps to keep the main flow in the South Branch.Thus,the main branch will not change in the near future because of the low sediment transport load.In this study,the flow-sediment process adjusted by the TGP was restored to the conditions before the TGP,and the river bed evolution under the adjusted and non-adjusted flow-sediment conditions was calculated.After the completion of the TGP,the reservoir storage accelerated the flood recession process and decreased the erosion by 11.9%under the flow-sediment conditions in 2010,and the deposition in the flood season decreased by 56.4%.
文摘Sediment research of TGP has been carried out for more than 40 years since 1958.This paper briefly describes the sediment research work of Yangtze River Scientific Research Institute in the reservoir area and damsite area of TGP in recent years.The research results demonstrate that sediment from Jinsha river and Jialing river reaches 83% of the total sediment at TGP.The completion of Xiluodu,Xiangjiaba and Tingzikou reservoirs will postpone the initial sediment balance time in TGP reservoir. In initial operation period of the project,the sediment in approach channels of the navigation structures can be cleared by machinery,in future period,the sediment outside the entrances of the upper and lower approach channels still need to be cleared by machinery while the sediment within the approach channel should be cleared by joint measures of flushing and mechanical dredging.
基金supported by the 322 Project of Vietnam International Education Development, Ministry of Education and Training, Vietnam (Grant No. 322)the Qing Lan Project, the 333 Project of Jiangsu Province (Grant No. BRA2012130)+1 种基金the Fundamental Research Funds for the Central Universities (Grant No.2012B06514)the 111 Project (Grant No. B12032)
文摘The Dinh An Estuary is one of the Nine Dragon estuaries of the Mekong River. An international navigation channel was built in the estuary for vessels traveling from the South China Sea to the southwestern area of Vietnam and then to Phnom Penh, Cambodia. The morphological evolution of the navigation channel is complicated and unstable. The back siltation intensity in the navigation channel has largely increased and been concentrated in the curvature segments of the channel since 1980. In this study, based on simulation results and measured data, five key factors that influence the back siltation in the navigation channel were systematically analyzed. These factors included the increasing elevation gap between the channel and the nearby seabed, the disadvantageous hydrodynamic conditions, sediment transport, mixing of saltwater and freshwater, and wave effects in the navigation channel. It is shown that the back siltation to a large extent results from the low current velocity of the secondary ocean circulation, which often occurs in the curvature segments of the channel. Suspended sediment also settles in the channel due to the decrease of the current velocity and the sediment transport capacity when flow passes through the channel. The changes of hydrodynamic conditions are responsible for the majority of the severe siltation in the curvature segments of the navigation channel.
文摘Based on field investigations, this paper analyzes three types of harbour basinns and navigation channel excavated on seabed in Jiaozhou Bay, get a general rule of deposition for excavated trough, it found that pollution is one of crucial factors resulting in the deposition of the excavated trough in the east shore of Jiaozhou Bay. With these results, it predicted the annual deposition thickness for the excavated trough and disclosed the fact that it can't be deposited deadly during one storm. At the same time, with two-dimensional numerical model, it studied the effects of the excavated trough and the reclamation near shore on tidal cureent and said that the excavated trough can decrease the current velocity passing through the trough about 10- 15%, but only limited inside and near the trough and there are no effect on other regions; reclamation can cut off the pollution sources and no obvious effect on the currents of the Jiaozhou Bay. Connecting the deep trough and Cangkou tidal channel with a new excavated trough can improve the current conditions on the deep trough in some degree, but not great.
文摘This paper, after briefly reviewing the experimental research on sediment transport on muddy beach since the 1950s, improves and perfects the method for forecasting siltation in navigation channels and harbour basins which was first put forward in China by the authors. In consideration of silty sediment and sand, some factors in forecasting methods have been changed and modified. Consequently, the modified methods can be used either to compute siltation in navigation channels and harbour basins on muddy beach or to compute siltation and scouring in navigation channels and harbour basins on both silty beach and sandy beach. The verification of field data from eleven large, medium and small natural harbours shows a good agreement between the forecasting by the modified method and the natural conditions. Finally, the paper deals with the rational utilization of water area after the construction of the West Dyke in Lianyungang, the maintenance of water depth of the navigation channel at the entrance, siltation distribution, siltation in the navigation channel and harbour basin for ships of 100 thousand tonnnage. Results once again prove that the prospect of constructing Lianyungang Harbour into a deepwater harbour is bright.
文摘Liquefied Natural Gas (LNG) port is located at Abu Qir Bay on the northwestern coast of the Nile delta, Egypt. The port was constructed in 2004 to export liquefied natural gas worldwide. The offshore basins of this port including the turning and berthing areas (15-m depth) are connected to the deep water by a 15-m depth dredged channel that extends 4 km offshore. However, the navigation channel and its contiguous basins have experienced problematic shoaling that might affect the navigation activities of gas tankers. Sedimentation processes have been investigated by analyses of waves, currents, bathymetry, grain size of seabed and channel dimensions. Sedimentation rates are estimated using a developed numerical model. Sedimentation rate fluctuates between 0.048 × 106 m3/month and 0.388 × 106 m3/month, with an annual sedimentation rate of 1.977 × 106 m3/yr. The variance in the sedimentation rates between winter and summer resulted in increasing of current speed and direction flowing towards offshore. The sedimentation process is influenced by the temporal variability in the direction and intensity of the predominant waves, currents, orientation of navigation channel, basin breakwaters, seafloor morphology and sediment sources. Due to the geographic location of LNG port it lays within a sediment sink for sediments supplied from different alternating directions by several pathways, flowing towards the N-W, S-W, N-E, and S-E quadrants. Most of these currents components are substantially effective in transporting fine-grained sediment towards the navigation channel axis and contiguous basins. Together with these currents, the predominant NW and SE waves acting to agitate and stirrup sediments in the vicinity of the port, and thereby accelerating sedimentation rates.
基金the National Key R&D Program of China(Grant No.2017YFC0405400)the National Natural Science Foundation of China(Grant No.51979172)Innovation Team Project of Estuarine and Coastal Protection and Management(Grant No.Y220013).
文摘The morphological evolution characteristics of the North-South Passage area since the construction of the Yangtze Estuary Deepwater Navigation Channel Project(DNCP)are analyzed on the basis of the measured data.A twodimensional morphodynamics numerical model of the Yangtze Estuary is established to verify the morphological evolution of the North-South Passage under the influence of the DNCP and to predict the future evolution in the next 40 years.Data analysis shows that the North Passage has experienced rapid adjustment stages and adaptive stages after the construction of the DNCP.Slow erosion occurred along the main channel,and slow siltation could be observed in the area between the groins.The South Passage showed a state of upper section erosion and down section deposition.At present,the whole South Passage is in a slight erosion state.According to the numerical model,the eroding and silting speed of the North Passage will slow down in the future.The present state that erosion occurs in the main channel and siltation occurs between the groins will continue.The South Passage will still maintain upper section erosion and down section deposition in the future.Due to the main channel erosion of the North Passage and siltation of the South Passage,the sediment division ratio of the North Passage will increase in the future but still be smaller than 50%.After morphological evolution of 40 years,the direction of residual sediment transport caused by M2 and M4 tidal components in the North Passage has not changed,but the transport rate will decrease.It is considered that the morphological evolution of the North-South Passage could reach a relatively stable state after 40 years.
