The goal of land consolidation in China is still to develop agricultural production.The study of landscape effects of land consolidation projects(LCPs)faces many difficulties because of the lack of government's in...The goal of land consolidation in China is still to develop agricultural production.The study of landscape effects of land consolidation projects(LCPs)faces many difficulties because of the lack of government's interest and data.This paper,taking Tianmen City of Hubei Province in Central China as an example,presents a methodology for analyzing landscape effects of LCPs by GIS and Fragstats3.3.It describes landscape effects with indexes of Patch Density(PD),Largest Patch Index(LPI),Landscape Shape Index(LSI),Interspersion and Juxtaposition Index(IJI),Aggregation Index(AI),and Shannon's Diversity Index(SHDI),showing more regular shape,simpler structure and less habitat diversity after LCPs.It computes ten landscape indexes of four categories of patches including Cultivated Land,Road,Water Channel,and River and Pond.The indexes show that 1)cultivated land becomes more fragmental in patch area,less irregular in patch shape and more concentrated in block;2)the transport capacity of roads and irri-gation and drainage capacity of water channels have been improved;3)the landscape change of river and pond can be summarized as decreasing scale,more regular shape,reducing connectivity and diversity of the class.LCPs can facili-tate agricultural production as well as protect cultivated land and food security.However,it is doubted that the increase of cultivated land from LCPs results from the reducing in landscape diversity of water area.展开更多
Land subsidence severely threatens most of the coastal plains around the world where high productive industrial and agricultural activities and urban centers are concentrated. Coastal subsidence damages infrastructure...Land subsidence severely threatens most of the coastal plains around the world where high productive industrial and agricultural activities and urban centers are concentrated. Coastal subsidence damages infrastructures and exacerbates the effect of the sea-level rise at regional scale. Although it is a well-known process, there is still much more to be improved on the monitoring, mapping and modeling of ground movements, as well as the understanding of controlling mechanisms. The International Geoscience Programme recently approved an international project(IGCP 663) aiming to bring together worldwide researchers to share expertise on subsidence processes typically occurring in coastal areas and cities, including basic research, monitoring and observation, modelling and management. In this paper, we provide the research communities and potential stakeholders with the basic information to join the participating teams in developing this project. Specifically, major advances on coastal subsidence studies and information on well-known and new case studies of land subsidence in China, Italy, The Netherlands, Indonesia, Vietnam and Thailand are highlighted and summarized. Meanwhile, the networking, dissemination, annual meeting and field trip are briefly introduced.展开更多
Land subsidence is a worldwide geohazard consisting in the lowering of the ground surface due to natural and human-induced processes occurring in the shallow and deep subsoil.Over the last two decades,land subsidence ...Land subsidence is a worldwide geohazard consisting in the lowering of the ground surface due to natural and human-induced processes occurring in the shallow and deep subsoil.Over the last two decades,land subsidence has caused damages and widespread impacts to a variety of infrastructures in coastal cities(Ma et al.,2011;Liu et al.,2016;Minderhoud et al.,2018).展开更多
The Quaternary sediments in the Yangtze delta are loose and lack precise stratification marks in the lithology. Moreover, due to the limitations of dating methods, it is difficult for Quaternary cores to deliver accur...The Quaternary sediments in the Yangtze delta are loose and lack precise stratification marks in the lithology. Moreover, due to the limitations of dating methods, it is difficult for Quaternary cores to deliver accurate age constraints. Thus, it is a challenge to establish the Quaternary stratigraphic framework. Gravity core LZK1 was drilled on Hengsha Island, Shanghai, in the Yangtze delta, in 2012. The core was terminated at 403.83 m below the local land surface, the uppermost 291.2 m comprising a thick sequence of Quaternary sediments. This study investigated the stratigraphic subdivision and paleoenvironmental change of the Quaternary sediments. From bottom to top, the Quaternary stratigraphic sequence can be subdivided into the lower Pleistocene Anting Formation, Middle Pleistocene Jiading Formation, Upper Pleistocene Chuansha Formation and Nanhui Formation, Holocene Loutang Formation, Shanghai Formation, and Rudong Formation. According to this study, the Hengsha Island area was dominated by a freshwater lacustrine environment during the early Pleistocene, an alternation of shallow lake and shore lake environment during the Middle Pleistocene, a delta plain to lagoonal environment during the early Upper Pleistocene, a fluvial channel to floodplain environment from the LGM(Last Glacial Maximum) to the end of the Upper Pleistocene, and a delta environment during the Holocene.展开更多
Sea level rise （SLR） is a major projected threat of climate change that is expected to affect developing coastal cities located in estuarine delta regions, Shanghai is one such city, being located in the Yangtze Riv...Sea level rise （SLR） is a major projected threat of climate change that is expected to affect developing coastal cities located in estuarine delta regions, Shanghai is one such city, being located in the Yangtze River Delta （YRD）, It is difficult, however, for decision-makers to implement adaptation due to the uncer- tain causes, magnitudes, and timings of SLR behaviors, This paper attempts to map the causes and mag- nitudes of SLR behaviors on a decadal scale, We analyze the tidal level records from 11 tidal gauge stations and the corresponding bathymetry measurements around these stations since 1921, We identify three new SLR behaviors along the Shanghai coast due to anthropogenic geomorphologic changes （AGCs）, besides the well-known eustatic sea level rise （ESLR）, tectonic subsidence （TS）, and urban land subsidence （ULS）, The first new behavior is regional sea level rise （RSLR）, which occurs as a result of land reclamation and deep waterway regulation, The second is regional sea level fall （RSLF）, which occurs because the channel bed is eroded due to sediment supply decline in the river catchment, The last SLR behavior is local tidal datum rise （LTDR）. Thus, we project that the magnitude of SLR for the Shanghai coast ranges from 10 cm to 16 cm from 2011 to 2030, Clarifying SLR behaviors is important to aid local decision- makers in planning structural and non-structural measures to combat escalating flood damage costs in an estuarine delta system; this field is full of future challenges,展开更多
Constrained by complex imaging mechanism and extraordinary visual appearance,change detection with synthetic aperture radar(SAR)images has been a difficult research topic,especially in urban areas.Although existing st...Constrained by complex imaging mechanism and extraordinary visual appearance,change detection with synthetic aperture radar(SAR)images has been a difficult research topic,especially in urban areas.Although existing studies have extended from bi-temporal data pair to multi-temporal datasets to derive more plentiful information,there are still two problems to be solved in practical applications.First,change indicators constructed from incoherent feature only cannot characterize the change objects accurately.Second,the results of pixel-level methods are usually presented in the form of the noisy binary map,making the spatial change not intuitive and the temporal change of a single pixel meaningless.In this study,we propose an unsupervised man-made objects change detection framework using both coherent and incoherent features derived from multi-temporal SAR images.The coefficients of variation in timeseries incoherent features and the man-made object index(MOI)defined with coherent features are first combined to identify the initial change pixels.Afterwards,an improved spatiotemporal clustering algorithm is developed based on density-based spatial clustering of applications with noise(DBSCAN)and dynamic time warping(DTW),which can transform the initial results into noiseless object-level patches,and take the cluster center as a representative of the man-made object to determine the change pattern of each patch.An experiment with a stack of 10 TerraSAR-X images in Stripmap mode demonstrated that this method is effective in urban scenes and has the potential applicability to wide area change detection.展开更多
Urban cover-collapse sinkholes pose a significant global challenge due to their destructive impacts.Previous studies have identified groundwater fluctuations,subsurface soil conditions,pipeline leakage,precipitation,a...Urban cover-collapse sinkholes pose a significant global challenge due to their destructive impacts.Previous studies have identified groundwater fluctuations,subsurface soil conditions,pipeline leakage,precipitation,and subterranean construction activities as key contributors to these phenomena.However,unique geological settings across different urban environments lead to variations in the primary factors influencing sinkhole formation.This study focuses on Shanghai,a city notable for its extensive urbanization and rich historical context,to explore the dynamics of sinkholes within urbanized areas worldwide.We employ spatial analysis and statistical methods to examine data on sinkholes recorded in the past two decades in Shanghai,correlating these events with the city’s shallow sand layer,ground elevation,and proximity to surface water.Our goal is to identify the dominant factors governing sinkhole occurrence in Shanghai and to lay the groundwork for their effective scientific management and prevention.Key findings indicate that most sinkholes in the area are associated with a thin shallow sand layer,low to moderate ground elevations,and the absence of nearby rivers.Additionally,many sinkholes correlate with subterranean voids within the confined aquifer beneath the cohesive soil layer.The lack of historical river channels,obscured by urban development,also indirectly contributes to sinkhole formation.We recommend enhancing urban river management and drainage systems to mitigate potential damage from water accumulation.展开更多
A local survey was implemented at the newly constructed Shanghai Tianma 65-m radio telescope.In this article,the survey implementation and data analysis are described.Particularly,by application of coordinate transfor...A local survey was implemented at the newly constructed Shanghai Tianma 65-m radio telescope.In this article,the survey implementation and data analysis are described.Particularly,by application of coordinate transformation,dimensionality reduction and step fitting of parameters,as well as adoption of reliability test measures of parameters,the mathematical model of data analysis is simplified,the detrimental effects of observation noises and unevenly spatial coverage of sample points are effectively compressed,the stability and precision of parameter solutions are improved,and so the geocentric three-dimensional coordinates of the reference point of this telescope in the precision of millimeters were determined,and the axisoffset was shown not significant on the precision level of3 mm.The outcome provides important reference to the subsequent activities of antenna maintenance and scientific application,including the establishment of precise antenna orientation model,orientation guidance,fringe searching in data cross-correlation,analysis and application studies of VLBI observations.It is also important archive data for monitoring possible subsidence and lateral displacement of antenna foundation as well as deformation of antenna tracking-rail and structure.展开更多
Land subsidence can be observed with time-series of Interferometric Synthetic Aperture Radar(InSAR)data.However,existing approaches only reveal subsidence signals that are multi-scale mixed,which is not conducive to t...Land subsidence can be observed with time-series of Interferometric Synthetic Aperture Radar(InSAR)data.However,existing approaches only reveal subsidence signals that are multi-scale mixed,which is not conducive to the systematic analysis of subsidence of different mechanisms.A deformation signal decomposition(DSD)method based on spectral analysis is used to decompose the deformation extracted by time-series InSAR into three classes of deformation signals.They refer to large-scale deformation related to geological settings,medium-scale deformation caused more by group excavation,and small-scale deformation along linear infrastructures.TerraSAR-X datasets for Shanghai spanning April 2013 to September 2020,and Sentinel-1A datasets spanning January 2016 to September 2020 are used in this study.The results were cross-verified between the TerraSAR-X and Sentinel-1A datasets,and validated against levelling measurements.Subsidence signals caused by different mechanisms were automatically decomposed,which facilitates a systematic analysis for targeted diagnosis of land subsidence signals.A detailed analysis was conducted jointly at three scales of surface displacement,geological conditions,major construction activities,and subsidence mechanisms.It indicated that construction activities were the leading cause of land subsidence,and suggests that local authorities that wish to mitigate surface subsidence may benefit from primarily considering this process.展开更多
The reform of urban master planning should make continuous progress to meet the requirements of urban and rural spatial resource control in the urbanization transformation period, considering its role of both strategi...The reform of urban master planning should make continuous progress to meet the requirements of urban and rural spatial resource control in the urbanization transformation period, considering its role of both strategic guidance and rigid control. As urban development in Shanghai is entering the era of stock-based development, it is important for the Shanghai 2040 Master Plan to upgrade urban strategies to adapt to the transformation environment of urban development, and to adjust the master planning system in line with Shanghai's reality. This article analyzes the development environment and challenges faced by the Shanghai 2040 Master Plan and reflects on the limitations of traditional master planning. To facilitate the spatial development transformation and spatial governance, the article summarizes the innovation ideas of the Shanghai 2040 Master Plan from aspects of functions, outcome framework, control system, organization format, etc.展开更多
Using CRU high resolution grid observational temperature and ERA40 reanalysis surface air temperature data during 1960–1999, we investigated the sensitivity of surface air temperature change to land use/cover types i...Using CRU high resolution grid observational temperature and ERA40 reanalysis surface air temperature data during 1960–1999, we investigated the sensitivity of surface air temperature change to land use/cover types in China by subtracting the reanalysis from the observed surface air temperature (observation minus reanalysis, OMR). The results show that there is a stable and systemic impact of land use/cover types on surface air temperature. The surface warming of each land use/cover type reacted differently to global warming. The OMR trends of unused land (?0.17 °C/decade), mainly comprised by sandy land, Gobi and bare rock gravel land, are obviously larger than those of the other land use/cover types. The OMR over grassland, farmland and construction land shows a moderate decadal warmingabout 0.12°C/decade, 0.10°C/decade, 0.12°C/decade, respectively. Woodland areas do not show a significant warming trend (0.06°C/decade). The overall assessment indicates that the surface warming is larger for areas that are barren and anthropogenically developed. The better the vegetation cover, the smaller the OMR warming trend. Responses of surface air temperature to land use/cover types with similar physical and chemical properties and biological processes have no significant difference. The surface air temperature would not react significantly until the intensity of land cover changes reach a certain degree. Within the same land use/cover type, areas in eastern China with intensive human activities exhibit larger warming trend. The results provide observational evidence for modeling research on the impact of land use/cover change on regional climate. Thus, projecting further surface climate of China in regional scale should not only take greenhouse gas increase into account, but also consider the impact of land use/cover types and land cover change.展开更多
Investigation of the deformation characteristics of individual hydrostratigraphic units is the key to construct a regional land subsidence model. All of 12 hydrostratigraphic units in the study area were discussed thr...Investigation of the deformation characteristics of individual hydrostratigraphic units is the key to construct a regional land subsidence model. All of 12 hydrostratigraphic units in the study area were discussed throughout. On the basis of the measured data of groundwater level, five kinds of changing patterns of groundwater level were deduced and the relationship between the deformation characteris-tics of aquifer units and the corresponding changing patterns of groundwater level was discussed. The study area is 1.7×104 km2, where the geological condition is complex. The changing patterns of groundwater level the hydrostratigraphic units have experienced vary from site to site and from time to time. Consequently, the deformation characteristics of units are sophisticated. An identical hydros-tratigraphic unit may exhibit different deformation characteristics, such as elasticity, elasto-plasticity, visco-elasticity, and visco-elasto-plasticity, at different sites or during different periods, not to mention the different units. The existing models are difficult to describe the complex visco-elasto-plastic con-stitutive law under the condition of land subsidence. So the Merchant’s model was modified to depict the visco-elasto-plastic behavior of units. Then a three-dimensional flow model with variable parame-ters and a vertical one-dimensional subsidence model were constructed and coupled. The coupled model was applied in simulating land subsidence in the southern Yangtze Delta and a satisfactory re-sult was obtained. The simulation results show that the new coupled model can depict the complex geological conditions and describe the developing process of land subsidence very well in the south-ern Yangtze Delta. The new model can surely be used to predict land subsidence in the future, which is very helpful to taking measurements to control land subsidence.展开更多
Attempt has been made to discuss the coupling relation of neotectonism and paleoclimate that have played a critical role in controlling the Quaternary sediment distribu-tion and sedimentary facies evolution on the Yan...Attempt has been made to discuss the coupling relation of neotectonism and paleoclimate that have played a critical role in controlling the Quaternary sediment distribu-tion and sedimentary facies evolution on the Yangtze coast. On the basis of petrological analysis, up to six sedimentary cyclicities have been identified in the Quaternary sediment boreholes on the time scale of 0.4―0.5 Ma. The lower sedi-mentary cyclicities (Pliocene to Early Pleistocene) are char-acterized largely by thicker gravelly coarse sands, topped by thinner fine silt and silty clay. Gravels are very angular and clayey gravels prevail. Sediments are usually of poor sorting, rich in log fragments and have no microfossils. Bedload as denoted by C-M plot occurs throughout the section. This evidence represents the alluvial fan sedimentation which took place as the basin began to subside. The middle sedimentary cyclicities (often including Early to Middle Pleistocene) con-sist of basal gravelly sands and clayey silt at the middle and upper sediment sections. Sorting becomes relatively better, and foraminifer appears sporadically. C-M plot reveals the mixture of sediment transport media via bedload, saltation and suspension, representing sedimentation of braided river system at the early stage and subsequently, the sedimentation of meandering river pattern. The upper sedimentary cyclic-ities (including Late Pleistocene to Holocene) comprise basal gravelly sands (exclusive of the Holocene sediment) and thick fine sand and silty clay on the upper section. Sorting becomes fine and foraminifer appears throughout the sediment sec-tion. C-M plot shows that saltation and suspension serve as the main sediment transport media in the sediment section and bedload transport weakens. These evidence the sedi-mentation of meandering river pattern near coast during Late Pleistocene and Holocene time, when marine transgres-sion invaded into the paleoriver valleys, which often forms drowned-valley facies and shallow marine facies. Of note is the Recent delta facies developed on the top of the cyclicities, and characterized by a large proportion of fine sand and siltyclay, and various sedimentary beddings. These phenomena have proved enhanced climate function on sedimentary fa-cies evolution on the basis of previous alluvial fan system, largely affected by tectonic subsidence setting.展开更多
Metros are critical infrastructure in big cities and evaluation of their safe operation is of increasing im-portance.To make a reasonable safety evaluation for the metro during operation,this paper establishes a ratio...Metros are critical infrastructure in big cities and evaluation of their safe operation is of increasing im-portance.To make a reasonable safety evaluation for the metro during operation,this paper establishes a rational safety evaluation model based on long-term monitoring data of Shanghai Metro Line 2.Four evaluation indicators,ie.,absolute settlement,relative curvature,deformation rate and curvature radius,are adopted.Analytic hierar-chy process(AHP)and entropy method are combined to determine the weights of the indicators.The risk level values at different mileage are calculated and five danger levels are defined accordingly to determine the safety state of Shanghai Metro Line 2,ie.,safe,relatively safe,critical,relatively dangerous,and dangerous.Safety evaluation of Shanghai Metro Line 2 shows that:83.81%areas of Shanghai Metro Line 2 are in safe,relatively safe and critical states,while 15.63%and 0.57%areas are in relatively dangerous and dangerous states,respectively;the parts of Shanghai Metro Line 2 where the risk level values exceed the critical value are mainly distributed around the mileage at 6.0-7.5km and 8.5-11.0 km,and the risk level value peaks around the mileage at 7.3km,to which much attention should be attached and relevant protective measures be taken;the sections with the high risk level values coincide with the distinctly deforming arcas of the metro,indicating that this evaluation method is valid.展开更多
The estuary is highly dynamic and sensitive to external and internal forcing.We examine a chain reaction of hydrody-namic and morphodynamic responses to a series of land reclamation projects during the period 1997 to ...The estuary is highly dynamic and sensitive to external and internal forcing.We examine a chain reaction of hydrody-namic and morphodynamic responses to a series of land reclamation projects during the period 1997 to 2017 in the North Branch of the Changjiang Estuary through the Digital Elevation Model(DEM)comparison and the numerical simulation by the Finite Volume Community Ocean Model(FVCOM).The results show that tidal amplification was fur-ther strengthened by the artificially reduced channel volume in the middle and upper segments of the North Branch due to the implementation of several large-scale land-reclamation projects in the first stage(1997-2007),and the channel siltation in the middle and upper segments was in turn further promoted by the increased tidal flows with flood dominance.In the second stage(2007-2017),tidal amplification was relaxed by the channel narrowing project at the lower segment and the waterway improvement project through channel dredging works at the middle and upper segments.Contemporary erosion volume was almost balanced by the accretion volume in the North Branch because of the weakening dominance of flood over ebb flows.Spatiotemporal variation in channel accretion and erosion patterns in response to estuarine engineering projects was vividly mirrored by the change of simulated bed shear stress in that the areas with increased(decreased)bed shear stress underwent severe erosion(accretion).These findings highlight again the dynamic feature of tide-dominated estuaries and the importance of simulation tools to the estuarine management.展开更多
基金Under the auspices of National Natural Science Foundation of China (No. 70673097)
文摘The goal of land consolidation in China is still to develop agricultural production.The study of landscape effects of land consolidation projects(LCPs)faces many difficulties because of the lack of government's interest and data.This paper,taking Tianmen City of Hubei Province in Central China as an example,presents a methodology for analyzing landscape effects of LCPs by GIS and Fragstats3.3.It describes landscape effects with indexes of Patch Density(PD),Largest Patch Index(LPI),Landscape Shape Index(LSI),Interspersion and Juxtaposition Index(IJI),Aggregation Index(AI),and Shannon's Diversity Index(SHDI),showing more regular shape,simpler structure and less habitat diversity after LCPs.It computes ten landscape indexes of four categories of patches including Cultivated Land,Road,Water Channel,and River and Pond.The indexes show that 1)cultivated land becomes more fragmental in patch area,less irregular in patch shape and more concentrated in block;2)the transport capacity of roads and irri-gation and drainage capacity of water channels have been improved;3)the landscape change of river and pond can be summarized as decreasing scale,more regular shape,reducing connectivity and diversity of the class.LCPs can facili-tate agricultural production as well as protect cultivated land and food security.However,it is doubted that the increase of cultivated land from LCPs results from the reducing in landscape diversity of water area.
基金financial support provided by the Shanghai Science and Technology Commission (No. 18DZ1201100)Shanghai Municipal Bureau of Human Resources and Social Security (Proj. Study on land subsidence mechanism and safety warning in new land reclamation area).
文摘Land subsidence severely threatens most of the coastal plains around the world where high productive industrial and agricultural activities and urban centers are concentrated. Coastal subsidence damages infrastructures and exacerbates the effect of the sea-level rise at regional scale. Although it is a well-known process, there is still much more to be improved on the monitoring, mapping and modeling of ground movements, as well as the understanding of controlling mechanisms. The International Geoscience Programme recently approved an international project(IGCP 663) aiming to bring together worldwide researchers to share expertise on subsidence processes typically occurring in coastal areas and cities, including basic research, monitoring and observation, modelling and management. In this paper, we provide the research communities and potential stakeholders with the basic information to join the participating teams in developing this project. Specifically, major advances on coastal subsidence studies and information on well-known and new case studies of land subsidence in China, Italy, The Netherlands, Indonesia, Vietnam and Thailand are highlighted and summarized. Meanwhile, the networking, dissemination, annual meeting and field trip are briefly introduced.
文摘Land subsidence is a worldwide geohazard consisting in the lowering of the ground surface due to natural and human-induced processes occurring in the shallow and deep subsoil.Over the last two decades,land subsidence has caused damages and widespread impacts to a variety of infrastructures in coastal cities(Ma et al.,2011;Liu et al.,2016;Minderhoud et al.,2018).
基金funded by the Geological Survey of China(Nos.DD20190370,DD20160345-07)the National Natural Science Foundation(No.40902049)。
文摘The Quaternary sediments in the Yangtze delta are loose and lack precise stratification marks in the lithology. Moreover, due to the limitations of dating methods, it is difficult for Quaternary cores to deliver accurate age constraints. Thus, it is a challenge to establish the Quaternary stratigraphic framework. Gravity core LZK1 was drilled on Hengsha Island, Shanghai, in the Yangtze delta, in 2012. The core was terminated at 403.83 m below the local land surface, the uppermost 291.2 m comprising a thick sequence of Quaternary sediments. This study investigated the stratigraphic subdivision and paleoenvironmental change of the Quaternary sediments. From bottom to top, the Quaternary stratigraphic sequence can be subdivided into the lower Pleistocene Anting Formation, Middle Pleistocene Jiading Formation, Upper Pleistocene Chuansha Formation and Nanhui Formation, Holocene Loutang Formation, Shanghai Formation, and Rudong Formation. According to this study, the Hengsha Island area was dominated by a freshwater lacustrine environment during the early Pleistocene, an alternation of shallow lake and shore lake environment during the Middle Pleistocene, a delta plain to lagoonal environment during the early Upper Pleistocene, a fluvial channel to floodplain environment from the LGM(Last Glacial Maximum) to the end of the Upper Pleistocene, and a delta environment during the Holocene.
基金This study was financially supported by the National Natural Science Foundation of China-the Netherlands Organization for Scientific Research-Research Councils UK （NSFC-NWO-RCUK） （51761135023）, the Shanghai Science and Technology Committee （10dz1210600）, the National Sea Welfare Project （201005019- 09）, the National Natural Science Foundation of China （41476075）, and the China Geological Survey （DD20160246）. We would like to give a special acknowledgement to the second author, ProfessorJi-Yu Chen, who was a great scientist of estuarine and coastal research, for the excellent suggestions and guidelines he provided over a considerable period of time before he passed away.
文摘Sea level rise （SLR） is a major projected threat of climate change that is expected to affect developing coastal cities located in estuarine delta regions, Shanghai is one such city, being located in the Yangtze River Delta （YRD）, It is difficult, however, for decision-makers to implement adaptation due to the uncer- tain causes, magnitudes, and timings of SLR behaviors, This paper attempts to map the causes and mag- nitudes of SLR behaviors on a decadal scale, We analyze the tidal level records from 11 tidal gauge stations and the corresponding bathymetry measurements around these stations since 1921, We identify three new SLR behaviors along the Shanghai coast due to anthropogenic geomorphologic changes （AGCs）, besides the well-known eustatic sea level rise （ESLR）, tectonic subsidence （TS）, and urban land subsidence （ULS）, The first new behavior is regional sea level rise （RSLR）, which occurs as a result of land reclamation and deep waterway regulation, The second is regional sea level fall （RSLF）, which occurs because the channel bed is eroded due to sediment supply decline in the river catchment, The last SLR behavior is local tidal datum rise （LTDR）. Thus, we project that the magnitude of SLR for the Shanghai coast ranges from 10 cm to 16 cm from 2011 to 2030, Clarifying SLR behaviors is important to aid local decision- makers in planning structural and non-structural measures to combat escalating flood damage costs in an estuarine delta system; this field is full of future challenges,
基金supported by the National Natural Science Foundation of China(41774006)the Comparative Study of Geo-environment and Geohazards in the Yangtze River Delta and the Red River Delta Projectthe Shanghai Science and Technology Development Foundation(20dz1201200)。
文摘Constrained by complex imaging mechanism and extraordinary visual appearance,change detection with synthetic aperture radar(SAR)images has been a difficult research topic,especially in urban areas.Although existing studies have extended from bi-temporal data pair to multi-temporal datasets to derive more plentiful information,there are still two problems to be solved in practical applications.First,change indicators constructed from incoherent feature only cannot characterize the change objects accurately.Second,the results of pixel-level methods are usually presented in the form of the noisy binary map,making the spatial change not intuitive and the temporal change of a single pixel meaningless.In this study,we propose an unsupervised man-made objects change detection framework using both coherent and incoherent features derived from multi-temporal SAR images.The coefficients of variation in timeseries incoherent features and the man-made object index(MOI)defined with coherent features are first combined to identify the initial change pixels.Afterwards,an improved spatiotemporal clustering algorithm is developed based on density-based spatial clustering of applications with noise(DBSCAN)and dynamic time warping(DTW),which can transform the initial results into noiseless object-level patches,and take the cluster center as a representative of the man-made object to determine the change pattern of each patch.An experiment with a stack of 10 TerraSAR-X images in Stripmap mode demonstrated that this method is effective in urban scenes and has the potential applicability to wide area change detection.
基金funded by the Shanghai Science and Technology Commission(project num.19DZ1200902)National Natural Science Foundation of China(Grant No.42076081).
文摘Urban cover-collapse sinkholes pose a significant global challenge due to their destructive impacts.Previous studies have identified groundwater fluctuations,subsurface soil conditions,pipeline leakage,precipitation,and subterranean construction activities as key contributors to these phenomena.However,unique geological settings across different urban environments lead to variations in the primary factors influencing sinkhole formation.This study focuses on Shanghai,a city notable for its extensive urbanization and rich historical context,to explore the dynamics of sinkholes within urbanized areas worldwide.We employ spatial analysis and statistical methods to examine data on sinkholes recorded in the past two decades in Shanghai,correlating these events with the city’s shallow sand layer,ground elevation,and proximity to surface water.Our goal is to identify the dominant factors governing sinkhole occurrence in Shanghai and to lay the groundwork for their effective scientific management and prevention.Key findings indicate that most sinkholes in the area are associated with a thin shallow sand layer,low to moderate ground elevations,and the absence of nearby rivers.Additionally,many sinkholes correlate with subterranean voids within the confined aquifer beneath the cohesive soil layer.The lack of historical river channels,obscured by urban development,also indirectly contributes to sinkhole formation.We recommend enhancing urban river management and drainage systems to mitigate potential damage from water accumulation.
基金supported by the National Natural Science Foundation of China (11178024 and 11373060)the Lunar Exploration of China (Chang’E 3)+1 种基金the Committee of Science and Technology of Shanghai (06DZ22101)the National High Technology Research and Development Program of China (2012AA121603)
文摘A local survey was implemented at the newly constructed Shanghai Tianma 65-m radio telescope.In this article,the survey implementation and data analysis are described.Particularly,by application of coordinate transformation,dimensionality reduction and step fitting of parameters,as well as adoption of reliability test measures of parameters,the mathematical model of data analysis is simplified,the detrimental effects of observation noises and unevenly spatial coverage of sample points are effectively compressed,the stability and precision of parameter solutions are improved,and so the geocentric three-dimensional coordinates of the reference point of this telescope in the precision of millimeters were determined,and the axisoffset was shown not significant on the precision level of3 mm.The outcome provides important reference to the subsequent activities of antenna maintenance and scientific application,including the establishment of precise antenna orientation model,orientation guidance,fringe searching in data cross-correlation,analysis and application studies of VLBI observations.It is also important archive data for monitoring possible subsidence and lateral displacement of antenna foundation as well as deformation of antenna tracking-rail and structure.
基金supported by the National Natural Science Foundation of China[grant number 42101450]the Open Fund of State Key Laboratory of Information Engineering in Surveying,Mapping and Remote Sensing,Wuhan University[grant number 21R03]the Comparative Study of Geo-environment and Geohazards in the Yangtze River Delta and the Red River Delta Project,the Shanghai Science and Technology Development Foundation[grant number 20dz1201200].
文摘Land subsidence can be observed with time-series of Interferometric Synthetic Aperture Radar(InSAR)data.However,existing approaches only reveal subsidence signals that are multi-scale mixed,which is not conducive to the systematic analysis of subsidence of different mechanisms.A deformation signal decomposition(DSD)method based on spectral analysis is used to decompose the deformation extracted by time-series InSAR into three classes of deformation signals.They refer to large-scale deformation related to geological settings,medium-scale deformation caused more by group excavation,and small-scale deformation along linear infrastructures.TerraSAR-X datasets for Shanghai spanning April 2013 to September 2020,and Sentinel-1A datasets spanning January 2016 to September 2020 are used in this study.The results were cross-verified between the TerraSAR-X and Sentinel-1A datasets,and validated against levelling measurements.Subsidence signals caused by different mechanisms were automatically decomposed,which facilitates a systematic analysis for targeted diagnosis of land subsidence signals.A detailed analysis was conducted jointly at three scales of surface displacement,geological conditions,major construction activities,and subsidence mechanisms.It indicated that construction activities were the leading cause of land subsidence,and suggests that local authorities that wish to mitigate surface subsidence may benefit from primarily considering this process.
文摘The reform of urban master planning should make continuous progress to meet the requirements of urban and rural spatial resource control in the urbanization transformation period, considering its role of both strategic guidance and rigid control. As urban development in Shanghai is entering the era of stock-based development, it is important for the Shanghai 2040 Master Plan to upgrade urban strategies to adapt to the transformation environment of urban development, and to adjust the master planning system in line with Shanghai's reality. This article analyzes the development environment and challenges faced by the Shanghai 2040 Master Plan and reflects on the limitations of traditional master planning. To facilitate the spatial development transformation and spatial governance, the article summarizes the innovation ideas of the Shanghai 2040 Master Plan from aspects of functions, outcome framework, control system, organization format, etc.
基金Supported by National Basic Research Program of China (Grant No. 2005CB422006)National Natural Science Foundation of China (Grant Nos. 90202012, 40771206)
文摘Using CRU high resolution grid observational temperature and ERA40 reanalysis surface air temperature data during 1960–1999, we investigated the sensitivity of surface air temperature change to land use/cover types in China by subtracting the reanalysis from the observed surface air temperature (observation minus reanalysis, OMR). The results show that there is a stable and systemic impact of land use/cover types on surface air temperature. The surface warming of each land use/cover type reacted differently to global warming. The OMR trends of unused land (?0.17 °C/decade), mainly comprised by sandy land, Gobi and bare rock gravel land, are obviously larger than those of the other land use/cover types. The OMR over grassland, farmland and construction land shows a moderate decadal warmingabout 0.12°C/decade, 0.10°C/decade, 0.12°C/decade, respectively. Woodland areas do not show a significant warming trend (0.06°C/decade). The overall assessment indicates that the surface warming is larger for areas that are barren and anthropogenically developed. The better the vegetation cover, the smaller the OMR warming trend. Responses of surface air temperature to land use/cover types with similar physical and chemical properties and biological processes have no significant difference. The surface air temperature would not react significantly until the intensity of land cover changes reach a certain degree. Within the same land use/cover type, areas in eastern China with intensive human activities exhibit larger warming trend. The results provide observational evidence for modeling research on the impact of land use/cover change on regional climate. Thus, projecting further surface climate of China in regional scale should not only take greenhouse gas increase into account, but also consider the impact of land use/cover types and land cover change.
基金the National Natural Science Foundation of China (Grant No. 40335045)
文摘Investigation of the deformation characteristics of individual hydrostratigraphic units is the key to construct a regional land subsidence model. All of 12 hydrostratigraphic units in the study area were discussed throughout. On the basis of the measured data of groundwater level, five kinds of changing patterns of groundwater level were deduced and the relationship between the deformation characteris-tics of aquifer units and the corresponding changing patterns of groundwater level was discussed. The study area is 1.7×104 km2, where the geological condition is complex. The changing patterns of groundwater level the hydrostratigraphic units have experienced vary from site to site and from time to time. Consequently, the deformation characteristics of units are sophisticated. An identical hydros-tratigraphic unit may exhibit different deformation characteristics, such as elasticity, elasto-plasticity, visco-elasticity, and visco-elasto-plasticity, at different sites or during different periods, not to mention the different units. The existing models are difficult to describe the complex visco-elasto-plastic con-stitutive law under the condition of land subsidence. So the Merchant’s model was modified to depict the visco-elasto-plastic behavior of units. Then a three-dimensional flow model with variable parame-ters and a vertical one-dimensional subsidence model were constructed and coupled. The coupled model was applied in simulating land subsidence in the southern Yangtze Delta and a satisfactory re-sult was obtained. The simulation results show that the new coupled model can depict the complex geological conditions and describe the developing process of land subsidence very well in the south-ern Yangtze Delta. The new model can surely be used to predict land subsidence in the future, which is very helpful to taking measurements to control land subsidence.
基金This study was supported by the N ational Natural Science Foundation of China(Grant No.4034 1009)APN(Asia Pacific Networks)START(SysTem Analysis Research and Training)(Grant No.2004-06_CMY).
文摘Attempt has been made to discuss the coupling relation of neotectonism and paleoclimate that have played a critical role in controlling the Quaternary sediment distribu-tion and sedimentary facies evolution on the Yangtze coast. On the basis of petrological analysis, up to six sedimentary cyclicities have been identified in the Quaternary sediment boreholes on the time scale of 0.4―0.5 Ma. The lower sedi-mentary cyclicities (Pliocene to Early Pleistocene) are char-acterized largely by thicker gravelly coarse sands, topped by thinner fine silt and silty clay. Gravels are very angular and clayey gravels prevail. Sediments are usually of poor sorting, rich in log fragments and have no microfossils. Bedload as denoted by C-M plot occurs throughout the section. This evidence represents the alluvial fan sedimentation which took place as the basin began to subside. The middle sedimentary cyclicities (often including Early to Middle Pleistocene) con-sist of basal gravelly sands and clayey silt at the middle and upper sediment sections. Sorting becomes relatively better, and foraminifer appears sporadically. C-M plot reveals the mixture of sediment transport media via bedload, saltation and suspension, representing sedimentation of braided river system at the early stage and subsequently, the sedimentation of meandering river pattern. The upper sedimentary cyclic-ities (including Late Pleistocene to Holocene) comprise basal gravelly sands (exclusive of the Holocene sediment) and thick fine sand and silty clay on the upper section. Sorting becomes fine and foraminifer appears throughout the sediment sec-tion. C-M plot shows that saltation and suspension serve as the main sediment transport media in the sediment section and bedload transport weakens. These evidence the sedi-mentation of meandering river pattern near coast during Late Pleistocene and Holocene time, when marine transgres-sion invaded into the paleoriver valleys, which often forms drowned-valley facies and shallow marine facies. Of note is the Recent delta facies developed on the top of the cyclicities, and characterized by a large proportion of fine sand and siltyclay, and various sedimentary beddings. These phenomena have proved enhanced climate function on sedimentary fa-cies evolution on the basis of previous alluvial fan system, largely affected by tectonic subsidence setting.
基金the National Natural Science Founda-tion of China(Nos.41602283 and 41977216)the Science and Technology Rising-Star Program of Shang-hai(No.19QC1400800)。
文摘Metros are critical infrastructure in big cities and evaluation of their safe operation is of increasing im-portance.To make a reasonable safety evaluation for the metro during operation,this paper establishes a rational safety evaluation model based on long-term monitoring data of Shanghai Metro Line 2.Four evaluation indicators,ie.,absolute settlement,relative curvature,deformation rate and curvature radius,are adopted.Analytic hierar-chy process(AHP)and entropy method are combined to determine the weights of the indicators.The risk level values at different mileage are calculated and five danger levels are defined accordingly to determine the safety state of Shanghai Metro Line 2,ie.,safe,relatively safe,critical,relatively dangerous,and dangerous.Safety evaluation of Shanghai Metro Line 2 shows that:83.81%areas of Shanghai Metro Line 2 are in safe,relatively safe and critical states,while 15.63%and 0.57%areas are in relatively dangerous and dangerous states,respectively;the parts of Shanghai Metro Line 2 where the risk level values exceed the critical value are mainly distributed around the mileage at 6.0-7.5km and 8.5-11.0 km,and the risk level value peaks around the mileage at 7.3km,to which much attention should be attached and relevant protective measures be taken;the sections with the high risk level values coincide with the distinctly deforming arcas of the metro,indicating that this evaluation method is valid.
基金the Innovation Program of Shanghai Municipal Education Commission(2021-01-07-00-07-E00093)the National Natural Science Foundation of China(NSFC-41976070,41730531).
文摘The estuary is highly dynamic and sensitive to external and internal forcing.We examine a chain reaction of hydrody-namic and morphodynamic responses to a series of land reclamation projects during the period 1997 to 2017 in the North Branch of the Changjiang Estuary through the Digital Elevation Model(DEM)comparison and the numerical simulation by the Finite Volume Community Ocean Model(FVCOM).The results show that tidal amplification was fur-ther strengthened by the artificially reduced channel volume in the middle and upper segments of the North Branch due to the implementation of several large-scale land-reclamation projects in the first stage(1997-2007),and the channel siltation in the middle and upper segments was in turn further promoted by the increased tidal flows with flood dominance.In the second stage(2007-2017),tidal amplification was relaxed by the channel narrowing project at the lower segment and the waterway improvement project through channel dredging works at the middle and upper segments.Contemporary erosion volume was almost balanced by the accretion volume in the North Branch because of the weakening dominance of flood over ebb flows.Spatiotemporal variation in channel accretion and erosion patterns in response to estuarine engineering projects was vividly mirrored by the change of simulated bed shear stress in that the areas with increased(decreased)bed shear stress underwent severe erosion(accretion).These findings highlight again the dynamic feature of tide-dominated estuaries and the importance of simulation tools to the estuarine management.
