A new expression for calculating suspended fine-sediment deposition rate is developed based on theoretic analysis and experiments. The resulting equation is applied to simulation of fine sediment deposition in the rec...A new expression for calculating suspended fine-sediment deposition rate is developed based on theoretic analysis and experiments. The resulting equation is applied to simulation of fine sediment deposition in the reclaimed land in the Hangzhou Bay, China. The hydrodynamic environment in this area is solved by use of a long wave model, which gives the 2D-velocity field and considers bathymetric changes due to fine sediment deposition. The expression is proved convenient to use in engineering practice, and the predicted deposition rate agrees with the annual data available from field measurements from the first year to the third year after the construction of the long groin as a reclaiming method.展开更多
Two depositional processes controlled the muddy sediments in the South China Sea Basin. Bathyal sediments depositional rate was 7.66 cm/la in the northern continental slope of the Basin where turbidity current was alm...Two depositional processes controlled the muddy sediments in the South China Sea Basin. Bathyal sediments depositional rate was 7.66 cm/la in the northern continental slope of the Basin where turbidity current was almost nonexistent. In the northern margin of the Basin, abyssal sediment depositional rate was 5.05cm/ka and turbidity current occurrence averaged 0.22 per 1000 years. Turbidite was found in the middle of the Basin. Over half of the muddy sediments in the deep sea basin were deposited by turbidity currents, and had typically graded bedding, and contents of organic matter, calcareous material and micropaleontologic species inconsistent with the environment.展开更多
According to the hydrographic and sediment data, the dynamic sedimentation characteristics are dealt with based on the analyses of the hydra-dynamics and the suspended and bottom sediment characters in Xiashimen (XSM)...According to the hydrographic and sediment data, the dynamic sedimentation characteristics are dealt with based on the analyses of the hydra-dynamics and the suspended and bottom sediment characters in Xiashimen (XSM) strait channel mouth area in the eastern part of Zhoushan Islands. It is pointed out that both of the changes of the hydra-dynamics and the fine sediment supply from Changjiang estuary result in the sedimentation mechanism of mainly the fine sediments flocculating deposition and secondly the coarser sediment deposition in single grain. The dynamic sedimentation characteristics are developed under the action of the deposition mechanism and reworking differences in different bedform areas.展开更多
As there are many heavily sedimentladen rivers in China, with high sediment concentration and a large quantity of sediment load, the sedimentation problems of the reservoirs built on those rivers are so serious that t...As there are many heavily sedimentladen rivers in China, with high sediment concentration and a large quantity of sediment load, the sedimentation problems of the reservoirs built on those rivers are so serious that the amount of sediment deposited in the reservoirs is great and the rate of sedimentation is accelerated. According to the statistics, up to the end of 1981, a total amount of 11.5×109m3 of sediment were accumulated in those reservoirs, i.e. 14.2% of the total designed capacity were lost. The average annual loss in storage capacity reached 2.3 percent, being the highest in the world. Silting of impounding lakes not only has an effect on the benefits of the reservoirs and seriously threatens the life of reservoirs, but also results in many environmental problems which were not fully estimated in the planning of the reservoirs. In this paper, the situation of reservoir deposition in China are described from the following aspects: 1) the characteristics of hydrology and sediment of the rivers; 2) the seriousness of reservoir sedimentation in China; 3) problems caused by reservoir deposition; 4) the methods of minimizing sediment deposition, etc.展开更多
文摘A new expression for calculating suspended fine-sediment deposition rate is developed based on theoretic analysis and experiments. The resulting equation is applied to simulation of fine sediment deposition in the reclaimed land in the Hangzhou Bay, China. The hydrodynamic environment in this area is solved by use of a long wave model, which gives the 2D-velocity field and considers bathymetric changes due to fine sediment deposition. The expression is proved convenient to use in engineering practice, and the predicted deposition rate agrees with the annual data available from field measurements from the first year to the third year after the construction of the long groin as a reclaiming method.
文摘Two depositional processes controlled the muddy sediments in the South China Sea Basin. Bathyal sediments depositional rate was 7.66 cm/la in the northern continental slope of the Basin where turbidity current was almost nonexistent. In the northern margin of the Basin, abyssal sediment depositional rate was 5.05cm/ka and turbidity current occurrence averaged 0.22 per 1000 years. Turbidite was found in the middle of the Basin. Over half of the muddy sediments in the deep sea basin were deposited by turbidity currents, and had typically graded bedding, and contents of organic matter, calcareous material and micropaleontologic species inconsistent with the environment.
文摘According to the hydrographic and sediment data, the dynamic sedimentation characteristics are dealt with based on the analyses of the hydra-dynamics and the suspended and bottom sediment characters in Xiashimen (XSM) strait channel mouth area in the eastern part of Zhoushan Islands. It is pointed out that both of the changes of the hydra-dynamics and the fine sediment supply from Changjiang estuary result in the sedimentation mechanism of mainly the fine sediments flocculating deposition and secondly the coarser sediment deposition in single grain. The dynamic sedimentation characteristics are developed under the action of the deposition mechanism and reworking differences in different bedform areas.
文摘As there are many heavily sedimentladen rivers in China, with high sediment concentration and a large quantity of sediment load, the sedimentation problems of the reservoirs built on those rivers are so serious that the amount of sediment deposited in the reservoirs is great and the rate of sedimentation is accelerated. According to the statistics, up to the end of 1981, a total amount of 11.5×109m3 of sediment were accumulated in those reservoirs, i.e. 14.2% of the total designed capacity were lost. The average annual loss in storage capacity reached 2.3 percent, being the highest in the world. Silting of impounding lakes not only has an effect on the benefits of the reservoirs and seriously threatens the life of reservoirs, but also results in many environmental problems which were not fully estimated in the planning of the reservoirs. In this paper, the situation of reservoir deposition in China are described from the following aspects: 1) the characteristics of hydrology and sediment of the rivers; 2) the seriousness of reservoir sedimentation in China; 3) problems caused by reservoir deposition; 4) the methods of minimizing sediment deposition, etc.
