The Inner Mongolia reaches of the Yellow River face problems of severe sedimen- tation caused by a variety of complex factors. The sedimentation process in those reaches has been characterized using the sediment balan...The Inner Mongolia reaches of the Yellow River face problems of severe sedimen- tation caused by a variety of complex factors. The sedimentation process in those reaches has been characterized using the sediment balance method, and the key factors affecting the process have been analyzed using the correlation analysis method. The results show that during the period 1952-2012 the Bayangaole （Bayan Gol） to Toudaoguai reaches in Inner Mongolia have undergone successive processes of accumulative sedimentation, then relative balance, and then accumulative sedimentation once again. The total annual sedimentation is 12.0341×108 m^3, of which accumulations from July to October account for 95.1% and the reaches from Sanhuhekou to Toudaoguai account for 98.5%. The main factor affecting scouring and sedimentation of the Bayangaole to Sanhuhekou reaches is the combined water and sediment condition. The critical conditions for equilibrium are an incoming sediment co- efficient 〈 0.007 kg·s·m^-6 and a flow discharge 〉 700 m^3·s^-1. The main factor affecting scouring and sedimentation of the Sanhuhekou to Toudaoguai reaches is the incoming sediment from the tributaries on the south bank and the combined water and sediment condition of the main stream. The critical conditions of the main stream for maintaining equilibrium status are a flow discharge of the main stream exceeding 800 m^3·s^-1 and a comprehensive incoming sediment coefficient 〈 0.005 kg^-3·m^-6. The incoming sediment from the tributaries has little impact on the main stream when the annual sediment load is less than 0.1 ×10^8 t. The incoming sediment coefficient of the main stream and the incoming sediment from the tributaries both play vital roles in the riverbed evolution of the Inner Mongolia reaches, but the latter contributes the most.展开更多
Due to safety concerns and habitat restoration for landlocked salmon,a 13-m high check dam on Chijiawan Creek was removed in late May 2011 in Taiwan.We conducted experiments to understand channel evolution of differen...Due to safety concerns and habitat restoration for landlocked salmon,a 13-m high check dam on Chijiawan Creek was removed in late May 2011 in Taiwan.We conducted experiments to understand channel evolution of different scenarios.We further compared our experimental results of riverbed elevation changes with the analytical solutions derived from the diffusion equation and field dynamics as well after the creek experienced the first flood event.The results indicated that magnitude of discharges and notch size are dominant factors in resulting channel evolution.While the largest differences between grain size distribution are associated with discharge,the largest differences in net change in upstream volume are associated with notch size.While the theoretical equation could help understand the channel change after dam removal,it only explained the evolution closer to the dam.The physical experiments,on the other hand,provided insights especially with regard to comparing alternative proposed management actions.The discrepancies between predicted and actual outcome highlight more needed inputs for future dam-removal assessments.展开更多
文摘The Inner Mongolia reaches of the Yellow River face problems of severe sedimen- tation caused by a variety of complex factors. The sedimentation process in those reaches has been characterized using the sediment balance method, and the key factors affecting the process have been analyzed using the correlation analysis method. The results show that during the period 1952-2012 the Bayangaole （Bayan Gol） to Toudaoguai reaches in Inner Mongolia have undergone successive processes of accumulative sedimentation, then relative balance, and then accumulative sedimentation once again. The total annual sedimentation is 12.0341×108 m^3, of which accumulations from July to October account for 95.1% and the reaches from Sanhuhekou to Toudaoguai account for 98.5%. The main factor affecting scouring and sedimentation of the Bayangaole to Sanhuhekou reaches is the combined water and sediment condition. The critical conditions for equilibrium are an incoming sediment co- efficient 〈 0.007 kg·s·m^-6 and a flow discharge 〉 700 m^3·s^-1. The main factor affecting scouring and sedimentation of the Sanhuhekou to Toudaoguai reaches is the incoming sediment from the tributaries on the south bank and the combined water and sediment condition of the main stream. The critical conditions of the main stream for maintaining equilibrium status are a flow discharge of the main stream exceeding 800 m^3·s^-1 and a comprehensive incoming sediment coefficient 〈 0.005 kg^-3·m^-6. The incoming sediment from the tributaries has little impact on the main stream when the annual sediment load is less than 0.1 ×10^8 t. The incoming sediment coefficient of the main stream and the incoming sediment from the tributaries both play vital roles in the riverbed evolution of the Inner Mongolia reaches, but the latter contributes the most.
文摘Due to safety concerns and habitat restoration for landlocked salmon,a 13-m high check dam on Chijiawan Creek was removed in late May 2011 in Taiwan.We conducted experiments to understand channel evolution of different scenarios.We further compared our experimental results of riverbed elevation changes with the analytical solutions derived from the diffusion equation and field dynamics as well after the creek experienced the first flood event.The results indicated that magnitude of discharges and notch size are dominant factors in resulting channel evolution.While the largest differences between grain size distribution are associated with discharge,the largest differences in net change in upstream volume are associated with notch size.While the theoretical equation could help understand the channel change after dam removal,it only explained the evolution closer to the dam.The physical experiments,on the other hand,provided insights especially with regard to comparing alternative proposed management actions.The discrepancies between predicted and actual outcome highlight more needed inputs for future dam-removal assessments.
