Taking TM images, SPOT photos and DEM images as the basic information, this paper had not only put forward a kind of manual controlled computer-automatic extraction method, but also completed the task of extracting th...Taking TM images, SPOT photos and DEM images as the basic information, this paper had not only put forward a kind of manual controlled computer-automatic extraction method, but also completed the task of extracting the main types of ground objects in the Three Gorges Reservoir area under relatively high accuracy, after finishing such preprocessing tasks as correcting the topographical spectrum and synthesizing the data. Taking the specialized image analysis software-eCognition as the platform, the research achieved the goal of classifying through choosing samples, picking out the best wave bands, and producing the identifying functions. At the same time the extraction process partly dispelled the influence of such phenomena as the same thing with different spectrums, different things with the same spectrum, border transitions, etc. The research did certain exploration in the aspect of technological route and method of using automatic extraction of the remote sensing image to obtain the information of land cover for the regions whose ground objects have complicated spectrums.展开更多
In the purple hilly region, erosions and landslides are all serious, and it is of great scientific value and practical significance to study their formation mechanism and distribution features there. In this paper, so...In the purple hilly region, erosions and landslides are all serious, and it is of great scientific value and practical significance to study their formation mechanism and distribution features there. In this paper, soil micromorphological methods and techniques were used to study the erosion zonal distribution in the region. The results indicated: (1) According to erosion process, the spacial distribution zones of the erosions and landslides in the purple hilly region with different solums were divided into scouring erosion zone, transport-diffusion zone, rocks and soil turbulence zone and sediment-bury zone; (2) The soil micromorphologic taxonomic feature identifying different erosion-landslide zone were found by studying the soil micromorphology of erosive zone in purple hilly region; (3) As for the erosion–landslide formation in the region, besides the external factors, the internal factors were found more important and favorable for landslide formation through the studies on the micormorphological features of slide soil.展开更多
The dry-hot valley of the Jinsha River is one of the typical eco-fragile areas in Southwest China, as well as a focus of revegetation study in the upper and middle reaches of the Changjiang River. Due to its extremely...The dry-hot valley of the Jinsha River is one of the typical eco-fragile areas in Southwest China, as well as a focus of revegetation study in the upper and middle reaches of the Changjiang River. Due to its extremely dry and hot climate, severely degraded vegetation and the intense soil and water loss, there are extreme difficulties in vegetation restoration in this area and no great breakthrough has ever been achieved on studies of revegetation over the last several decades. Through over ten years’ research conducted in the typical areas-the Yuanmou dry-hot valley, the authors found that the lithologic property is one of the crucial factors determining soil moisture conditions and vegetation types in the dry-hot valley, and the rainfall infiltration capability is also one of the key factors affecting the tree growth. Then the revegetation zoning based on different slopes was conducted and revegetation patterns for different zones were proposed.展开更多
Tibet is located at the southwest boundary of China. It is the main body of the Qinghai-Tibet Plateau, the highest and the youngest plateau in the world. Owing to complicated geology, Neo-tectonic movements, geomorpho...Tibet is located at the southwest boundary of China. It is the main body of the Qinghai-Tibet Plateau, the highest and the youngest plateau in the world. Owing to complicated geology, Neo-tectonic movements, geomorphology, climate and plateau environment, various mountain hazards, such as debris flow, flash flood, landslide, collapse, snow avalanche and snow drifts, are widely distributed along the Jinsha River (the upper reaches of the Yangtze River), the Nu River and the Lancang River in the east, and the Yarlungzangbo River, the Pumqu River and the Poiqu River in the south and southeast of Tibet. The distribution area of mountain hazards in Tibet is about 589,000 km2, 49.3% of its total territory. In comparison to other mountain regions in China, mountain hazards in Tibet break out unexpectedly with tremendously large scale and endanger the traffic lines, cities and towns, farmland, grassland, mountain environment, and make more dangers to the neighboring countries, such as Nepal, India, Myanmar and Bhutan. To mitigate mountain hazards, some suggestions are proposed in this paper, such as strengthening scientific research, enhancing joint studies, hazards mitigation planning, hazards warning and forecasting, controlling the most disastrous hazards and forbidding unreasonable human exploring activities in mountain areas.展开更多
Three soil cores collected from China and UK show the 210Pbex and 137Cs depth distribution on uncultivated and cultivated land. Depth distributions of the two nuclides are very similar. Those nuclide concentrations ar...Three soil cores collected from China and UK show the 210Pbex and 137Cs depth distribution on uncultivated and cultivated land. Depth distributions of the two nuclides are very similar. Those nuclide concentrations are higher in the top horizon and decrease exponentially with depth on uncultivated land while the concentrations are almost uni-form throughout the plough layer as a result of mixing asso-ciated with cultivation on cultivated land. 210Pbex reference inventory in the Loess Plateau is 573 mBq·cm-2, a little higher than 520.0 mBq·cm-2 in UK. Distribution of artificial fallout 137Cs, produced during the nuclear testing period of the late 1950s and 1960s, is in an unsteady state. In contrast, distribution of natural fallout 210Pbex is in a steady state un-der constant conditions of land environment and erosion processes for a long term, e.g. >100 years. Therefore, mass balances of 137Cs and 210Pbex in soil are different. According to its processes of continues deposition from the atmosphere, nature decay and losses with soil losses, 210Pbex steady state mass balance models for cultivated land as well as for uncul-tivated land are developed to estimate soil erosion rates in this paper. Besides, the proportion of freshly deposited 210Pbex fallout removed by erosion on cultivated land can also be calculated from 210Pbex depth distribution at a reference site of uneroded permanent grass land.展开更多
Abstract By comparison of volumes and 137Cs contents of the deposited sediments before and after 1993, changes of specific sediment yields and relative sediment contributions from the gully area and from the inter gul...Abstract By comparison of volumes and 137Cs contents of the deposited sediments before and after 1993, changes of specific sediment yields and relative sediment contributions from the gully area and from the inter gully area after closing cultivation on the later area on a small catchment of Zhaojia Gully, in the Rolling Loess Plateau, are analyzed in this paper. Closing cultivation in a large scale has not resulted in decrease but increase of specific sediment yield of the catchment, in sharp decrease of the sediment yield and the relative sediment contribution of the inter-gully area, and in increase of the sediment yield and the contribution of the gully area, for a short term. The mean specific sediment yield of 29650 t km-2 a-1 of 1994—1996 in the catchment was 2.2 times the average value of 13413 t km-2 a-1 for a long term. The specific sediment yield of the inter-gully area decreased from the 14335 t km-2 a-1 in 1994 to 7034 t km-2 a-1 in 1995 and 3517 t km-2 a-1 in 1996, while the yield of the gully area varied between 44944 and 62136 t km-2 a-1 during the period of 1994—1996 which was much greater than the value of 21118 t km-2 a-1 before 1993. The relative sediment contribution from the inter-gully area decreased from 23% in 1994 to 15% in 1995 and 6% in 1996, while the contribution from the gully area increased from 77% in 1994 to 85% in 1995 and 94% in 1996. It is suggested that compacting of ploughed soils resulted in increasing of the erosion resistance but in decreasing of the precipitation infiltration, therefore, the soil erosion reduced but the runoff amount increased on the inter-gully area. Increase of delivering runoff from the inter-gully area to the gully area should result in activeness of gully erosion and mass movements, consequently, in increase of the total sediment yield from the catchment.展开更多
The transition process of intermittent flow in a longitudinal section of Bingham fluid from initial distribu-tion to fully developed state was numerically investigated in this paper. The influences of slope ,J dimensi...The transition process of intermittent flow in a longitudinal section of Bingham fluid from initial distribu-tion to fully developed state was numerically investigated in this paper. The influences of slope ,J dimensionless runoff Q* and viscosity m*0on the dimensionless surge speed U* were also presented in a wide range of parameters. By one typical example, the intermittent flow possessed wave char-acteristics and showed a supercritical flow conformation for a fully developed flow. The distributions of gravity and bed drag along the flow path and the velocity distribution of flow field were also analyzed.展开更多
基金Under the auspices of the Construction Committeeof Three GorgesR eservoirProject(No .SX [2002]00401) andChineseAcademy ofSciences(No .KZCX2-SW-319-01 )
文摘Taking TM images, SPOT photos and DEM images as the basic information, this paper had not only put forward a kind of manual controlled computer-automatic extraction method, but also completed the task of extracting the main types of ground objects in the Three Gorges Reservoir area under relatively high accuracy, after finishing such preprocessing tasks as correcting the topographical spectrum and synthesizing the data. Taking the specialized image analysis software-eCognition as the platform, the research achieved the goal of classifying through choosing samples, picking out the best wave bands, and producing the identifying functions. At the same time the extraction process partly dispelled the influence of such phenomena as the same thing with different spectrums, different things with the same spectrum, border transitions, etc. The research did certain exploration in the aspect of technological route and method of using automatic extraction of the remote sensing image to obtain the information of land cover for the regions whose ground objects have complicated spectrums.
基金supported by the Knowledge Innovation Project of the Chinese Academy of Sciences(KZCX3-SW-330)the State Natural Science Foundation for Outstanding Personnel of China(40025103)
文摘In the purple hilly region, erosions and landslides are all serious, and it is of great scientific value and practical significance to study their formation mechanism and distribution features there. In this paper, soil micromorphological methods and techniques were used to study the erosion zonal distribution in the region. The results indicated: (1) According to erosion process, the spacial distribution zones of the erosions and landslides in the purple hilly region with different solums were divided into scouring erosion zone, transport-diffusion zone, rocks and soil turbulence zone and sediment-bury zone; (2) The soil micromorphologic taxonomic feature identifying different erosion-landslide zone were found by studying the soil micromorphology of erosive zone in purple hilly region; (3) As for the erosion–landslide formation in the region, besides the external factors, the internal factors were found more important and favorable for landslide formation through the studies on the micormorphological features of slide soil.
基金Under the auspices of the National Natural Science Foundation of China (No .30470297)and theNationalBasicRe-searchProgram ofChina (973 Program)(No .2003CB415201 )
文摘The dry-hot valley of the Jinsha River is one of the typical eco-fragile areas in Southwest China, as well as a focus of revegetation study in the upper and middle reaches of the Changjiang River. Due to its extremely dry and hot climate, severely degraded vegetation and the intense soil and water loss, there are extreme difficulties in vegetation restoration in this area and no great breakthrough has ever been achieved on studies of revegetation over the last several decades. Through over ten years’ research conducted in the typical areas-the Yuanmou dry-hot valley, the authors found that the lithologic property is one of the crucial factors determining soil moisture conditions and vegetation types in the dry-hot valley, and the rainfall infiltration capability is also one of the key factors affecting the tree growth. Then the revegetation zoning based on different slopes was conducted and revegetation patterns for different zones were proposed.
基金This research is supported by the West Key Research Project of the National Natural Science Foundation of China(No.90202007)the Researcher Introduced Project of Chengdu Institute of Mountain Hazards and Environment,the Chinese Academy of Sciences&Ministry of Water Conservancy(Y1006).
文摘Tibet is located at the southwest boundary of China. It is the main body of the Qinghai-Tibet Plateau, the highest and the youngest plateau in the world. Owing to complicated geology, Neo-tectonic movements, geomorphology, climate and plateau environment, various mountain hazards, such as debris flow, flash flood, landslide, collapse, snow avalanche and snow drifts, are widely distributed along the Jinsha River (the upper reaches of the Yangtze River), the Nu River and the Lancang River in the east, and the Yarlungzangbo River, the Pumqu River and the Poiqu River in the south and southeast of Tibet. The distribution area of mountain hazards in Tibet is about 589,000 km2, 49.3% of its total territory. In comparison to other mountain regions in China, mountain hazards in Tibet break out unexpectedly with tremendously large scale and endanger the traffic lines, cities and towns, farmland, grassland, mountain environment, and make more dangers to the neighboring countries, such as Nepal, India, Myanmar and Bhutan. To mitigate mountain hazards, some suggestions are proposed in this paper, such as strengthening scientific research, enhancing joint studies, hazards mitigation planning, hazards warning and forecasting, controlling the most disastrous hazards and forbidding unreasonable human exploring activities in mountain areas.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.40271015 and 900102017)the Stiate Key Laboratory of Loess and Quaternary Geology,Institute of Earth Environment,the Chinese Acatemy of Sciences(CAS)(Grant No.SKLLQG0206)+1 种基金the Knowledge Innovation Project of Water Erosion Prediction Modeling of CAS(Grant No.KZCX3-SW-422)IAEA(12322/RO).
文摘Three soil cores collected from China and UK show the 210Pbex and 137Cs depth distribution on uncultivated and cultivated land. Depth distributions of the two nuclides are very similar. Those nuclide concentrations are higher in the top horizon and decrease exponentially with depth on uncultivated land while the concentrations are almost uni-form throughout the plough layer as a result of mixing asso-ciated with cultivation on cultivated land. 210Pbex reference inventory in the Loess Plateau is 573 mBq·cm-2, a little higher than 520.0 mBq·cm-2 in UK. Distribution of artificial fallout 137Cs, produced during the nuclear testing period of the late 1950s and 1960s, is in an unsteady state. In contrast, distribution of natural fallout 210Pbex is in a steady state un-der constant conditions of land environment and erosion processes for a long term, e.g. >100 years. Therefore, mass balances of 137Cs and 210Pbex in soil are different. According to its processes of continues deposition from the atmosphere, nature decay and losses with soil losses, 210Pbex steady state mass balance models for cultivated land as well as for uncul-tivated land are developed to estimate soil erosion rates in this paper. Besides, the proportion of freshly deposited 210Pbex fallout removed by erosion on cultivated land can also be calculated from 210Pbex depth distribution at a reference site of uneroded permanent grass land.
基金This work was supported by the National Natural Science Foundation of China(Grant No.40271015)MST(Grant No.2001CCB00100)+2 种基金CAS(Grant Nos.KZCX3 SW-330 and KZCX3-SW-422)IAEA(12322/RO)State Key Laboratory of Soil Erosion and Dry Land Farming on the Loess Plateau(10501-109).
文摘Abstract By comparison of volumes and 137Cs contents of the deposited sediments before and after 1993, changes of specific sediment yields and relative sediment contributions from the gully area and from the inter gully area after closing cultivation on the later area on a small catchment of Zhaojia Gully, in the Rolling Loess Plateau, are analyzed in this paper. Closing cultivation in a large scale has not resulted in decrease but increase of specific sediment yield of the catchment, in sharp decrease of the sediment yield and the relative sediment contribution of the inter-gully area, and in increase of the sediment yield and the contribution of the gully area, for a short term. The mean specific sediment yield of 29650 t km-2 a-1 of 1994—1996 in the catchment was 2.2 times the average value of 13413 t km-2 a-1 for a long term. The specific sediment yield of the inter-gully area decreased from the 14335 t km-2 a-1 in 1994 to 7034 t km-2 a-1 in 1995 and 3517 t km-2 a-1 in 1996, while the yield of the gully area varied between 44944 and 62136 t km-2 a-1 during the period of 1994—1996 which was much greater than the value of 21118 t km-2 a-1 before 1993. The relative sediment contribution from the inter-gully area decreased from 23% in 1994 to 15% in 1995 and 6% in 1996, while the contribution from the gully area increased from 77% in 1994 to 85% in 1995 and 94% in 1996. It is suggested that compacting of ploughed soils resulted in increasing of the erosion resistance but in decreasing of the precipitation infiltration, therefore, the soil erosion reduced but the runoff amount increased on the inter-gully area. Increase of delivering runoff from the inter-gully area to the gully area should result in activeness of gully erosion and mass movements, consequently, in increase of the total sediment yield from the catchment.
基金supported by Special Project of the Fundamenta1 Research on Landslide and Debris Flows of the Chinese Academy of Sciencesthe National Natural Science Foundation of China(Grant No.49771003).
文摘The transition process of intermittent flow in a longitudinal section of Bingham fluid from initial distribu-tion to fully developed state was numerically investigated in this paper. The influences of slope ,J dimensionless runoff Q* and viscosity m*0on the dimensionless surge speed U* were also presented in a wide range of parameters. By one typical example, the intermittent flow possessed wave char-acteristics and showed a supercritical flow conformation for a fully developed flow. The distributions of gravity and bed drag along the flow path and the velocity distribution of flow field were also analyzed.