Debris flows are recurrent natural hazards in many mountainous regions.This paper presents a numerical study on the propagation of debris flows in natural erodible open channels,in which the bed erosion and sedimentat...Debris flows are recurrent natural hazards in many mountainous regions.This paper presents a numerical study on the propagation of debris flows in natural erodible open channels,in which the bed erosion and sedimentation processes are important.Based on the Bingham fluid theory,a mathematical model of the two-dimensional non-constant debris flow is developed.The governing equations include the continuity and momentum conservation equations of debris flow,the sediment convection-diffusion equation,the bed erosion-deposition equation and the bed-sediment size gradation adjustment equation.The yield stress and shear stress components are included to describe the dynamic rheological properties.The upwind control-volume Finite Volume Method (FVM) is applied to discretize the convection terms.The improved SIMPLE algorithm with velocity-free-surface coupled correction is developed to solve the equations on non-orthogonal,quadrilateral grids.The model is applied to simulate a debris flow event in Jiangjia Gully,Yunnan Province and to predict the flow pattern and bed erosion-deposition processes.The results show the effectiveness of the proposed numercial model in debris flow simulation and potential hazard analysis.展开更多
Sediment-associated processes, such as sediment erosion, deposition, and pore water diffusion/advection affect sorptive contaminant transport. By considering these processes, we developed an equation to simulate conta...Sediment-associated processes, such as sediment erosion, deposition, and pore water diffusion/advection affect sorptive contaminant transport. By considering these processes, we developed an equation to simulate contaminant transport. Erosion and deposition processes are considered as erosion and deposition fluxes of sediment, and adsorption-desorption processes of contaminants by sediment are simulated using the Langmuir Equation. Pore water diffusion is calculated based on the contaminant concentration gradient across the sediment-water interface. Pore water advection is estimated using pore water contained in the sediments of erosion flux. The equation is validated to simulate total phosphorus concentrations in Guanhe estuary in the northern Jiangsu, China. The simulated total phosphorus concentrations show better agreement with field observations compared to estimations that do consider sediment-associated processes.展开更多
The research works were carried out for determination of the washout, types, sorts and level of the development reasons of degradation with the purpose of preparation of the measures of fight against degradation in th...The research works were carried out for determination of the washout, types, sorts and level of the development reasons of degradation with the purpose of preparation of the measures of fight against degradation in the soils in 2005-2009 in the lowland of Kur-Araz. The investigations were fulfilled by using of geographical and stasionar methods. It is revealed that 333.6 thous, ha of the soils of the lowland of Kur-Araz have been exposed to erosion. 97.4 thousand ha of them have been exposed to rainstorm erosion, 127.1 thous, have been exposed to irrigative and 122.1 thous, ha to wind erosion. The most dangerous of them are considered irrigative erosion. Under the influence of erosion process in deposited over the length of furrow, deposits the changes happened in maintenance of humus and nutritions elements. In dependence on slope and water expenditure on 1 ha 2.23-14.86 t of soil are leached. As a result of out wash from 1 ha of soil 55.88-304.59 kg of humus, 4.06-20.80 kg of nitrogen, 4.57-26.55 of phosphorus and 57.40-372.99 of potassium are lost. The soil is exposed to degradation and as a result a process of desertification begins. On the basis of the quantitative an intensity of soil outwash the possible losses of dry matter including humus and main elements of nutrition of plants as a result of erosion, their deposit with the water way, are calculated, too.展开更多
The Tianshan Mountains,located in the northwestern China,are bounded by the Tarim Basin to south and the Junggar Basin to north.In the north piedmont of this mountain range,ongoing thrusting and folding forms a set of...The Tianshan Mountains,located in the northwestern China,are bounded by the Tarim Basin to south and the Junggar Basin to north.In the north piedmont of this mountain range,ongoing thrusting and folding forms a set of roughly parallel anticlines.Geological observations predicted that averaged over last^1 Ma time scale,the shortening rates of these anticlines are about2.1–5.5 mm/a;However by averaged over about 10±2 kyr,their shortening rates reduce to merely about 1.25±0.5 mm/a.The slow shortening of the anticlines in the last^10±2 kyr is coarsely concurrent in time with the last global deglaciation.Here,we use a two-dimensional finite element model to explore crustal deformation across north piedmont of the Tianshan Mountains under various erosion-sedimentation conditions that are assumed to represent the climate-controlled surface process.Numerical experiments show that with a relatively weak erosion-sedimentation strength,the crustal shortening is accommodated mainly by north piedmont of the Tianshan Mountains,similar to the high shortening rate of anticlines averaged over the last^1Ma.By increasing erosion-sedimentation strength,the resultant crustal shortening is transformed gradually toward the Tianshan Mountains,resulting in the shortening rate in its north piedmont being decelerated to what is observed as averaged over the last^10±2 kyr.This result suggests that erosion and sedimentation could play an important role mechanically on strain localization across an intra-continent active tectonic belt.Hence,if the climate change around the last global deglaciation could be simply representative to the enhancement of surface erosion and sedimentation across the pre-existed Tianshan Mountains and its foreland,our models indicate that the observed shortening-rate variations averaged over^1 Ma and^10±2kyr time scales around north piedmont of the Tianshan Mountains should be resulted from climate changes.展开更多
The Kaoping submarine canyon, connected to the Kaoping River in the coastal plain in SW Taiwan, continues the dispersal path of modern Kaoping River sediments, from an active small mountainous drain basin to the recei...The Kaoping submarine canyon, connected to the Kaoping River in the coastal plain in SW Taiwan, continues the dispersal path of modern Kaoping River sediments, from an active small mountainous drain basin to the receiving basin of the South China Sea. Using seismic reflection sections, Chirp sonar profiles, and bathymetric mapping, we reveal characteristic erosive processes responsible for multiple cut-and-fill features, deeply entrenched thalweg, and sediment dispersal that are closely related to turbidity currents in the canyon. The river-canyon connection setting, along with extreme climatic conditions and active tectonism, is favorable for generation of turbidity currents at the canyon head. The upper reach of the Kaoping Canyon is distinguished into three distinct morpho/sedimentary features. The canyon head is characterized by V-shaped axial thalweg erosion. The sinuous segment of the upper reach is dominated by a deeply incised canyon pathway with trough-like morphol- ogy. Relatively small-scaled features of cut-and-fill associated with the dominant incision process are commonly along the canyon floor, resulting in a flat-floored pathway. Sliding and slumping dominated the steep canyon walls, producing and transporting sediments to canyon floor and partially filling up canyon thalweg. The meandering segment is characterized by erosive features where deeply down-cutting occurs in the outer bend of the major sea valley, forming V-shaped entrenched thalweg. The recurrences of turbidity currents have allowed continuous incision of the canyon head and have kept the connec- tion between the canyon head and the river mouth during Holocene highstand of sea level. The upper reach of the Kaoping Canyon is linked to drainage area and maintains as a conduit and/or sink for terrigenous and shallow marine material. Sediment-laden river plume operates in the Kaoping River-Canyon system, with turbidity currents flushing fiver sediments into the canyon head where the canyon thalweg is the most erosive. Presently, the upper reach of the Kaoping Canyon can be considered as a temporal sediment sink.展开更多
基金supported by the National Basic Research Program of China (973 Program)(Grant No.2011CB409902)the Knowledge Innovation Project of the Chinese Academy of Sciences (No.KZCX2-YW-302)
文摘Debris flows are recurrent natural hazards in many mountainous regions.This paper presents a numerical study on the propagation of debris flows in natural erodible open channels,in which the bed erosion and sedimentation processes are important.Based on the Bingham fluid theory,a mathematical model of the two-dimensional non-constant debris flow is developed.The governing equations include the continuity and momentum conservation equations of debris flow,the sediment convection-diffusion equation,the bed erosion-deposition equation and the bed-sediment size gradation adjustment equation.The yield stress and shear stress components are included to describe the dynamic rheological properties.The upwind control-volume Finite Volume Method (FVM) is applied to discretize the convection terms.The improved SIMPLE algorithm with velocity-free-surface coupled correction is developed to solve the equations on non-orthogonal,quadrilateral grids.The model is applied to simulate a debris flow event in Jiangjia Gully,Yunnan Province and to predict the flow pattern and bed erosion-deposition processes.The results show the effectiveness of the proposed numercial model in debris flow simulation and potential hazard analysis.
基金Supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China(No.200802940014)
文摘Sediment-associated processes, such as sediment erosion, deposition, and pore water diffusion/advection affect sorptive contaminant transport. By considering these processes, we developed an equation to simulate contaminant transport. Erosion and deposition processes are considered as erosion and deposition fluxes of sediment, and adsorption-desorption processes of contaminants by sediment are simulated using the Langmuir Equation. Pore water diffusion is calculated based on the contaminant concentration gradient across the sediment-water interface. Pore water advection is estimated using pore water contained in the sediments of erosion flux. The equation is validated to simulate total phosphorus concentrations in Guanhe estuary in the northern Jiangsu, China. The simulated total phosphorus concentrations show better agreement with field observations compared to estimations that do consider sediment-associated processes.
文摘The research works were carried out for determination of the washout, types, sorts and level of the development reasons of degradation with the purpose of preparation of the measures of fight against degradation in the soils in 2005-2009 in the lowland of Kur-Araz. The investigations were fulfilled by using of geographical and stasionar methods. It is revealed that 333.6 thous, ha of the soils of the lowland of Kur-Araz have been exposed to erosion. 97.4 thousand ha of them have been exposed to rainstorm erosion, 127.1 thous, have been exposed to irrigative and 122.1 thous, ha to wind erosion. The most dangerous of them are considered irrigative erosion. Under the influence of erosion process in deposited over the length of furrow, deposits the changes happened in maintenance of humus and nutritions elements. In dependence on slope and water expenditure on 1 ha 2.23-14.86 t of soil are leached. As a result of out wash from 1 ha of soil 55.88-304.59 kg of humus, 4.06-20.80 kg of nitrogen, 4.57-26.55 of phosphorus and 57.40-372.99 of potassium are lost. The soil is exposed to degradation and as a result a process of desertification begins. On the basis of the quantitative an intensity of soil outwash the possible losses of dry matter including humus and main elements of nutrition of plants as a result of erosion, their deposit with the water way, are calculated, too.
基金supported by National Natural Science Foundation of China(Grant Nos.40474039,41030320)Chinese Academy of Sciences(Grant No.XDB030105)
文摘The Tianshan Mountains,located in the northwestern China,are bounded by the Tarim Basin to south and the Junggar Basin to north.In the north piedmont of this mountain range,ongoing thrusting and folding forms a set of roughly parallel anticlines.Geological observations predicted that averaged over last^1 Ma time scale,the shortening rates of these anticlines are about2.1–5.5 mm/a;However by averaged over about 10±2 kyr,their shortening rates reduce to merely about 1.25±0.5 mm/a.The slow shortening of the anticlines in the last^10±2 kyr is coarsely concurrent in time with the last global deglaciation.Here,we use a two-dimensional finite element model to explore crustal deformation across north piedmont of the Tianshan Mountains under various erosion-sedimentation conditions that are assumed to represent the climate-controlled surface process.Numerical experiments show that with a relatively weak erosion-sedimentation strength,the crustal shortening is accommodated mainly by north piedmont of the Tianshan Mountains,similar to the high shortening rate of anticlines averaged over the last^1Ma.By increasing erosion-sedimentation strength,the resultant crustal shortening is transformed gradually toward the Tianshan Mountains,resulting in the shortening rate in its north piedmont being decelerated to what is observed as averaged over the last^10±2 kyr.This result suggests that erosion and sedimentation could play an important role mechanically on strain localization across an intra-continent active tectonic belt.Hence,if the climate change around the last global deglaciation could be simply representative to the enhancement of surface erosion and sedimentation across the pre-existed Tianshan Mountains and its foreland,our models indicate that the observed shortening-rate variations averaged over^1 Ma and^10±2kyr time scales around north piedmont of the Tianshan Mountains should be resulted from climate changes.
基金supported under a grant of the "National" Science Council,Chinese Taiwan
文摘The Kaoping submarine canyon, connected to the Kaoping River in the coastal plain in SW Taiwan, continues the dispersal path of modern Kaoping River sediments, from an active small mountainous drain basin to the receiving basin of the South China Sea. Using seismic reflection sections, Chirp sonar profiles, and bathymetric mapping, we reveal characteristic erosive processes responsible for multiple cut-and-fill features, deeply entrenched thalweg, and sediment dispersal that are closely related to turbidity currents in the canyon. The river-canyon connection setting, along with extreme climatic conditions and active tectonism, is favorable for generation of turbidity currents at the canyon head. The upper reach of the Kaoping Canyon is distinguished into three distinct morpho/sedimentary features. The canyon head is characterized by V-shaped axial thalweg erosion. The sinuous segment of the upper reach is dominated by a deeply incised canyon pathway with trough-like morphol- ogy. Relatively small-scaled features of cut-and-fill associated with the dominant incision process are commonly along the canyon floor, resulting in a flat-floored pathway. Sliding and slumping dominated the steep canyon walls, producing and transporting sediments to canyon floor and partially filling up canyon thalweg. The meandering segment is characterized by erosive features where deeply down-cutting occurs in the outer bend of the major sea valley, forming V-shaped entrenched thalweg. The recurrences of turbidity currents have allowed continuous incision of the canyon head and have kept the connec- tion between the canyon head and the river mouth during Holocene highstand of sea level. The upper reach of the Kaoping Canyon is linked to drainage area and maintains as a conduit and/or sink for terrigenous and shallow marine material. Sediment-laden river plume operates in the Kaoping River-Canyon system, with turbidity currents flushing fiver sediments into the canyon head where the canyon thalweg is the most erosive. Presently, the upper reach of the Kaoping Canyon can be considered as a temporal sediment sink.