A comprehensive analysis is conducted based on observations on topography, tidal current, salinity, suspended sediment and bed load during the years of 1982, 1983, 1988, 1989. 1996, and 1997 in the Yangtze Estuary. Re...A comprehensive analysis is conducted based on observations on topography, tidal current, salinity, suspended sediment and bed load during the years of 1982, 1983, 1988, 1989. 1996, and 1997 in the Yangtze Estuary. Results show that the deformation of tidal waves is distinct and the sand carrying capacity is large within the mouth bar due to strong tidal currents and large volume of incoming water and sediments. Owing to both temporal and spatial variation of tidal current, deposition and erosion ore extremely active. In general a change of up to 0.1 m of bottom sediments takes place during a tidal period. The maximum siltation and erosion are around 0.2 m in a spring to neap tides cycle. The riverbed is silted during flood when there is heavy sediment load, eroded during dry season when sediment lo:ld is low. The annual average depth of erosion anti siltation on the riverbed is around 0.6 m. In particular cases, it may increase to 1.4 m to 2.4 m at some locations.展开更多
The objective of this study is to incorporate a numerical model with GIS to simulate the movement, erosion and deposition of debris flow across the three dimensional complex terrain. In light of the importance of eros...The objective of this study is to incorporate a numerical model with GIS to simulate the movement, erosion and deposition of debris flow across the three dimensional complex terrain. In light of the importance of erosion and deposition processes during debris flow movement, no entrainment assumption is unreasonable. The numerical model considering these processes is used for simulating debris flow. Raster grid networks of a digital elevation model in GIS provide a uniform grid system to describe complex topography. As the raster grid can be used as the finite difference mesh, the numerical model is solved numerically using the Leap-frog finite difference method. Finally, the simulation results can be displayed by GIS easily and used to debris flow evaluation. To illustrate this approach, the proposed methodology is applied to the Yohutagawa debris flow that occurred on 2oth October 2010, in Amami- Oshima area, Japan. The simulation results that reproduced the movement, erosion and deposition are in good agreement with the field investigation. The effectiveness of the dam in this real-ease is also verified by this approach. Comparison with the results were simulated by other models, shows that the present coupled model is more rational and effective.展开更多
Debris flow is a rapid flow which could lead to severe flooding with catastrophic consequences such as damage to properties and loss of human lives.It is important to study the movement of debris flow.Since during a d...Debris flow is a rapid flow which could lead to severe flooding with catastrophic consequences such as damage to properties and loss of human lives.It is important to study the movement of debris flow.Since during a debris flow process,the erosion and deposition processes are important,the no entrainment assumption is not acceptable.In this study,first we considered the debris flow as equivalent fluid and adopted the depth-averaged govern equations to simulate the movements and evolution of river bed.Secondly,the set of partial differential equations was solved numerically by means of explicit staggered leap-frog scheme that is accurate in space and time.The grid of difference scheme was derived from GIS raster data.Then the simulation results can be displayed by GIS and easily used to form the hazard maps.Finally,the numerical model coupled with GIS is applied to simulate the debris flow occurred on Oct.20th,2010,in Amamioshima City,Japan.The simulation reproduces the movement,erosion and deposition.The results are shown to be consistent with the field investigation.展开更多
基金This study is supported by the National Natural Science Foundation of China(Grant No.49736220)
文摘A comprehensive analysis is conducted based on observations on topography, tidal current, salinity, suspended sediment and bed load during the years of 1982, 1983, 1988, 1989. 1996, and 1997 in the Yangtze Estuary. Results show that the deformation of tidal waves is distinct and the sand carrying capacity is large within the mouth bar due to strong tidal currents and large volume of incoming water and sediments. Owing to both temporal and spatial variation of tidal current, deposition and erosion ore extremely active. In general a change of up to 0.1 m of bottom sediments takes place during a tidal period. The maximum siltation and erosion are around 0.2 m in a spring to neap tides cycle. The riverbed is silted during flood when there is heavy sediment load, eroded during dry season when sediment lo:ld is low. The annual average depth of erosion anti siltation on the riverbed is around 0.6 m. In particular cases, it may increase to 1.4 m to 2.4 m at some locations.
基金finanicial support from the Global Environment Research Fund of Japan(S-8)from Grants-in-Aid for Scientific Research(Scientific Research(B),22310113,G.Chen)from Japan Society for the Promotion of Science
文摘The objective of this study is to incorporate a numerical model with GIS to simulate the movement, erosion and deposition of debris flow across the three dimensional complex terrain. In light of the importance of erosion and deposition processes during debris flow movement, no entrainment assumption is unreasonable. The numerical model considering these processes is used for simulating debris flow. Raster grid networks of a digital elevation model in GIS provide a uniform grid system to describe complex topography. As the raster grid can be used as the finite difference mesh, the numerical model is solved numerically using the Leap-frog finite difference method. Finally, the simulation results can be displayed by GIS easily and used to debris flow evaluation. To illustrate this approach, the proposed methodology is applied to the Yohutagawa debris flow that occurred on 2oth October 2010, in Amami- Oshima area, Japan. The simulation results that reproduced the movement, erosion and deposition are in good agreement with the field investigation. The effectiveness of the dam in this real-ease is also verified by this approach. Comparison with the results were simulated by other models, shows that the present coupled model is more rational and effective.
基金This study was supported by the Global Environment Research Found of Japan(S-8)and Grants-in-Aid for Scientific Research(Scientific Research(B),22310113,G.Chen)from Japan Society for the Promotion of ScienceAnd the first author acknowledges the support of China Scholarship Council.These financial supports are gratefully acknowledged.
文摘Debris flow is a rapid flow which could lead to severe flooding with catastrophic consequences such as damage to properties and loss of human lives.It is important to study the movement of debris flow.Since during a debris flow process,the erosion and deposition processes are important,the no entrainment assumption is not acceptable.In this study,first we considered the debris flow as equivalent fluid and adopted the depth-averaged govern equations to simulate the movements and evolution of river bed.Secondly,the set of partial differential equations was solved numerically by means of explicit staggered leap-frog scheme that is accurate in space and time.The grid of difference scheme was derived from GIS raster data.Then the simulation results can be displayed by GIS and easily used to form the hazard maps.Finally,the numerical model coupled with GIS is applied to simulate the debris flow occurred on Oct.20th,2010,in Amamioshima City,Japan.The simulation reproduces the movement,erosion and deposition.The results are shown to be consistent with the field investigation.
