A Study on Flood Storage Capacity in Dongting Lake
LI Yi-tian, DENG Jin-yun,SUN
Zhao-hua, HE Yong
(Wuhan University, The Key Laboratory of Water and Sediment Sciences, Ministry of
Education)
Abstract: Based on the calculation results of the flood storage capacity in Dongting Lake from 1950's to 90's, the impact of sediment deposition in Dongting Lake and the reach from Chenglingji to Hankou and land use in the lake region on the flood storage capacity is analyzed. The study shows that sediment deposition in downstream reach is the main reason of flood storage increment under the same inflow condition.
Key words: sediment deposition; flood storage capacity; high flood level
Average Velocity and Acceleration Effects of Intermittent Debris Flows
XU Yong nian,KUANG Shang fu,SHU
An ping
(China Institute of Water Resources and Hydropower Research)
Abstract: In this paper,the authors discussed the definition and classification of debris flows, and studied the characteristics of different equation forms of debris flow motion. The authors considered that the average velocity formulas of debris flows accord with the Manning's formula.By using the annual observed data in Jiangjia channel,the authors analysed and verified the effect factors of the average velocity formulas of debris flows,such as the average coarse grain size, the concentration by volume, the thickness of unsteady layer,and relative gradient of slope,etc. Finally, the superimpose effect on the moving process of intermittent debris flows was diccussed.The authors pointed out that the supernormal pore water pressure between debris flows and underlay reduces resistance between debris flows and underlay,and accelerates debris flows,thereby the velocity of debris flows on mild slope can reach 15m/s.
Key words: intermittent debris flows; the average velocity; resistance decrease due to superimpose effect; acceleration effect
Study on Navigation Condition of Dajiang Downstream Channel of Gezhouba Project
ZHAO Lian-bai, LIU Wan-li, ZHANG
Xiu-qin
(Tianjin Research Institute for Water Transport Engineering)
Abstract: The navigation condition of Dajiang downstream channel in Gezhouba Project has been studied by analyzing the field data and model test. The main problems for navigation existed in the project and the influence of the project operation on the downstream channel were also studied. In addition, the paper predicted the influence of the operation of the Three Gorges Project on the riverbed evolution and flow pattern in Dajiang downstream reach.
Key words: Gezhouba project; navigation condition; engineering measures
JI Zu wen, HU Chun hong, TIAN
Qing qi, LIU Hai tao
(China Institute of Water Resources and Hydropower Research)
Abstract: According to the experimental data of the generalized physical model of the Lower Reach of Yellow River, some characteristics of bed evolution and sediment-carrying capacity under the different conditions of the dredging dimension and the oncoming runoff and sediment load are analyzed¡£In general, the variational ranges of water velocity, the scouring volume in the upper reach and the redepositing volume in the dredging channel will be bigger if the dredging dimension is larger. However, the redepositing rate and the dredging efficiency are a nonlinear relation. When the value of B/Hof the dredging channel is about 5-8, the dredging efficiency will be maximum. Under a constant dredging dimension, with the increase of the discharge or the reduction of the sediment concentration/the sediment size, the scouring volume in the upper reach will increase, whereas the re-deposition in the dredqing channel will decrease.
Key words: Yellow River; velocity; sediment; dredging channel; scouring and depositing volumes
Application of Multigrid Method in 2-D Numerical Model
CAO Zhi-fang, ZHAO Ming-deng, LI
Yi-tian
(Wuhan University, the Key Laboratory of Water and Sediment Sciences of Ministry of
Education)
Abstract: The convergent speed is one of the important reasons to affect the application of 2 D numerical models for unsteady flow and sediment transport. In this paper, a so-called multigrid method is used to improve the computational speed. Meanwhile, the coordinate transformation method is used to fit the complicated and irregular boundary conditions. The analysis to the iteration characteristic of the multigrid method by a case study shows that the method can greatly improve the numerical convergent speed. Finally, the proposed 2-D model was verified by using the field data in Wuhan reach of Yangtze River.
Key words: multigrid method; HFAM; coordinates transformation£»mathematical model
SHEN Guan-qing£¬QU Shao-jun£¬ZHANG Yuan-feng£¬LONG Yu-qian
(Institute of Hydraulic Research£¬YRCC)
Abstract: The change of water level is the reflection of the interaction between stream flow and river boundaries. The interactions are different for different rivers. For ordinary rivers, deformations of riverbed are not intensive and changes of water level depend mainly upon changes of discharge. For rivers with sediment-laden, such as the Yellow River, changing quickly of river boundaries, channel erosion and floodplain deposition, erosion in flooding up and deposition in flooding down are the main characteristics of river variation in flood period. Cross section regulation affects the change of water level greatly. In this paper the effect of main channel erosion on the capacity of average or low sediment concentration conveyance flood are analyzed from quality to quantity in details. The research result is very significant to guide flood protection of the Lower Yellow River.
Key words: the Lower Yellow River£» flood period£» main channel£» cross section regulation£»ability of flood transporting£» average or low sediment concentration flood
Experimental Study on Hydraulic Characteristics of Rill Flows over Clay Soil Slope
SHA Ji de1£¬BAI Qing jun2
£¨1.Northwest Science and Technology University of
Agriculture and Forest£»2. Shandong Agricultural
University£©
Abstract: The characteristics of rill flows occurred over clay soil slope were often described from the point of geography. Based on indoor experiments, the paper discussed the characteristics of rill flows from the point of minimum energy dissipation and hydraulics. Not only were the "drop pit" phenomena which occurred during the rill erosion analyzed, but also the differences in the hydraulic characteristics between rill flows and open channel flows were pointed out.
Key words: rill flow£»drop pit£»minimum energy dissipation£»hydraulic characteristics
Abstract:This paper is undertaken the phenomenon of the sand motion and scour-deposition on bottom panel by experimental tests with clear water.From experimental analysis,some results could be summarized as:(1)The depths of scour ds and deposition dd are larger as the ¦È is larger (¦Èis the angle between flow and panel).They may reach the maximum values as ¦È between 45¡ã and 60¡ã¡£However, when ¦È is greater than 60¡ã, the bigger the ¦È,the smaller the ds and dd.(2) A scouring hole close to panel moves backward and forward between upstream and downstream of panel center as ¦È increases gradually.(3) There is a linear positive relationship between ds or dd and h (h is the height from bed to top of panel)¡£(4) There is a linear positive relationship between ds/a and ¦È (a is the length of the scouring hole).
Key words: bottom panel; sand motion trained; scour; deposition
Abstract: The initiative project of channel dredging and dykes strengthenning in the lower Yellow River started in the reach of Zhujiawuzi¡«Qing No.2 on the November 23, 1997.Without doubt, it is an attempt to reduce river deposition in lower Yellow River. The affect of river channel dredging on water level, slope, and the cross sectional shape, etc. was analyzed based on the field observation of hydrology and sedimentation in 1998 flood season.
Key words: star up engineering; field observation; retrogressive erosion; streamwise erosion
Abstract: Based on the previous research, the mechanism of the consolidation of fly ash has been analyzed through the study on its incipient velocity, dry density, physical and chemical properties, and microstructure. In addition, the methods to control consolidation of fly ash are also discussed.
Key words: model sands; fly ash; consolidation; incipient velocity; dry density
Abstract: In order to select the route of Tonggu channel, the sediment transport in Tonggu sea area has been conducted for both natural condition and after the completion of Tonggu channel project. Not only did the results of physical and mathematical models verify the feasibility of the project, but also provide the plan to select the route.
Key words: Tonggu channel; deposition and erosion; sediment transport and diffusion
Abstract: Different types of land uses are the main reason to cause soil erosion. By taking the Baolongquan small basin in Hulunbeier League erodible region as an observation base, the analyses on the relationship among the precipitation, runoff, and soil erosion under different land uses are conducted. The results show that the soil erosion depends greatly on land uses, such as cultivated land along ridges, cultivated land across ridges, uncultivated slope fields, terraced fields, and the secondary forest land. In addition, the results indicate that the soil erosion is directly proportional to the rain runoff. These findings may provide a scientific basis for the prevention and management of the soil in the erodible region in Hulunbeier League.
Key words: land use in erodible region; runoff erosion; Hulunbeier League
XIA Jun-qiang, WANG Guang-qian,
ZHANG Hong-wu, FANG Hong-wei
(Key Laboratory of Water and Sediment Sciences of Education Ministry, Tsinghua University)
Abstract: This paper first describes the phenomena of channel widenning of alluvial rivers, and analyzes two kinds of mechanisms leading to lateral widenning, which are fluvial-controlled and non-fluvial-controlled mechanisms. Then mechanical relations and main effect factors causing lateral widenning are presented. Finally three kinds of approaches to simulating lateral widenning are systematically summarized, and their advantages,disadvantages and application limitation are analyzed.In addition, further study is suggested.
Key words: lateral widenning mechanisms; noncohesive riverbanks; cohesive riverbanks; approaches to simulating lateral widening
ÍøÒ³ÖÆ×÷£º |
