Hydrologic modeling is a popular tool for estimating the hydrological response of a watershed. However, modeling processes are becoming more complex due to land-use changes such as urbanization, industrialization, and...Hydrologic modeling is a popular tool for estimating the hydrological response of a watershed. However, modeling processes are becoming more complex due to land-use changes such as urbanization, industrialization, and the expansion of agricultural activities. The primary goal of the research was to use the HEC-HMS model to evaluate the impact of impervious soil layers and the increase in rainfall-runoff processes on hydrologic processes. For these purposes, the Watershed Modelling System (WMS) and Hydrologic Engineering Center’s-Hydrologic Modeling System (HEC-HMS) models were used in this study to simulate the rainfall-runoff process. To compute runoff rate, runoff volume, base flow, and flow routing methods SCS curve number, SCS unit hydrograph, recession, and loss routing methods were selected for the research, respectively. To reduce the processing time and computational complexity, a small section of the Pipestem Creek Watershed was selected to understand the methods and concepts associated with the hydrologic simulation model building. A DEM along with other required data such as land use land cover data, soil type data, and meteorological data was utilized to delineate the watershed in WMS. The output of WMS was utilized to run the HEC-HMS model for five different scenario analyses. All the relevant data were plugged in to the model to get the desired map. Subsequently, outlets at appropriate locations were selected for the sub-basin delineation for further analysis. Finally, the model was parametrized to get successful simulation results. Overall, peak discharges and runoff volumes were increased with increasing storm depths and impervious areas. Peak discharges were increased to 36% and 51% when rainfall depths were increased by 10% and 20% from the initial rainfall depth, respectively. Runoff volumes were also increased to 35% and 49% for the same scenarios, respectively. Peak discharges were increased to 12% and 78% with a 10% and 20%, respectively, increase in impervious areas. The runoff volumes were increased by 12% and 76% when impervious areas were increased by 10% and 20%, respectively. The simulation models responded well, and the peak discharges and runoff volumes increased with increasing storm depths and impervious areas.展开更多
The urban heat island(UHI) effect has significant effects on the quality of life and public health. Numerous studies have addressed the relationship between UHI and the increase in urban impervious surface area(ISA), ...The urban heat island(UHI) effect has significant effects on the quality of life and public health. Numerous studies have addressed the relationship between UHI and the increase in urban impervious surface area(ISA), but few of them have considered the impact of the spatial configuration of ISA on UHI. Land surface temperature(LST) may be affected not only by urban land cover, but also by neighboring land cover. The aim of this research was to investigate the effects of the abundance and spatial association of ISAs on LST. Taking Harbin City, China as an example, the impact of ISA spatial association on LST measurements was examined. The abundance of ISAs and the LST measurements were derived from Landsat Thematic Mapper(TM) imagery of 2000 and 2010, and the spatial association patterns of ISAs were calculated using the local Moran’s I index. The impacts of ISA abundance and spatial association on LST were examined using correlation analysis. The results suggested that LST has significant positive associations with both ISA abundance and the Moran’s I index of ISAs, indicating that both the abundance and spatial clustering of ISAs contribute to elevated values of LST. It was also found that LST is positively associated with clustering of high-ISA-percentage areas(i.e.,>50%) and negatively associated with clustering of low-ISA-percentage areas(i.e.,<25%). The results suggest that, in addition to the abundance of ISAs,their spatial association has a significant effect on UHIs.展开更多
This study focuses on the consolidation behavior and mathematical interpretation of partially-saturated ground improved by impervious column inclusion.The constitutive relations for soil skeleton,pore air and pore wat...This study focuses on the consolidation behavior and mathematical interpretation of partially-saturated ground improved by impervious column inclusion.The constitutive relations for soil skeleton,pore air and pore water for partially saturated soils are proposed in the context of partially-saturated ground improved by impervious column inclusion.Settlement equation and dissipation equations of excess pore air/water pressures for a partially saturated improved ground are then derived.The semi-analytical solutions for ground settlement and pore pressure dissipation are then obtained through the Laplace transform and validated by the existing solutions for two special cases in the literature and the numerical results obtained from the finite difference method.A series of parametric studies is finally conducted to investigate the influence of some key factors on consolidation of partially saturated ground improved by impervious column inclusion.Based on the parametric study,it can be found that a higher value of the area replacement ratio or modulus of the pile results in a longer dissipation time of excess pore air pressure(PAP),a shorter dissipation time of excess pore water pressure(PWP),and a lower normalized settlement.展开更多
The province of British Columbia, Canada, has established an Agricultural Land Reserve (ALR) to protect the most suitable soil landscapes for agriculture. Increases in population and urbanization have resulted in deve...The province of British Columbia, Canada, has established an Agricultural Land Reserve (ALR) to protect the most suitable soil landscapes for agriculture. Increases in population and urbanization have resulted in development challenges on ALR lands. The Metro Vancouver area is the most productive agricultural area in British Columbia as well as the most rapidly growing urban region. The increase in impervious areas has decreased the amount of arable land for soil-based agriculture and altered the hydrological cycle. Analysis using a combination of aerial imagery and GIS found that impervious areas comprise about 10 percent of the ALR within Metro Vancouver. Farm residences and greenhouses have the largest effect on reducing the soil surface for water infiltration. This decrease in area has negatively influenced the ecosystem heath of the region, as well as, decreasing the amount of agricultural land for soil based agriculture and both surface and groundwater dynamics.展开更多
This paper investigates the performance of geomembrane composites used as impervious andheat-insulating lining within a breakwater for a power station.The seepage field,distribution ofstress-strain contour and seepage...This paper investigates the performance of geomembrane composites used as impervious andheat-insulating lining within a breakwater for a power station.The seepage field,distribution ofstress-strain contour and seepage discharge of hot water which has been treated as the inner thermalsource in the calculation of heat-insulation,have been given by three-dimensional calculation method coup-ling seepage with stress.The results indicate that the impervious and heat-insulation effect ofgeomembrane composites is significant.展开更多
Asset management is a strategic decision-making aspect of social infra-structure that ensures safety by predicting long-term conditions and maximizing effectiveness under budgetary constraints. Predicting the deterior...Asset management is a strategic decision-making aspect of social infra-structure that ensures safety by predicting long-term conditions and maximizing effectiveness under budgetary constraints. Predicting the deterioration of impervious walls is essential in the asset management of coastal landfill sites, particularly in the design of their maintenance and repair strategy. In this paper, a quantitative evaluation of the leakage of toxic substances in coastal landfill sites where deterioration of side impervious walls has decreased the water interception performance is reported. In addition, risk evaluation based on the asset management of the leakage is applied to determine an appropriate repair method. The strategy of repairing the walls when the concentration of the toxic substances leaking into the sea area exceeds the closure and abandonment of coastal landfill sites is demonstrated to be superior. Moreover, the strategy of repairing only the seaside side impervious wall is shown to be cost-effective.展开更多
The urban environment has continued to experience changes from increasing impervious surfaces, which alters the proper functioning of the ecological zones and impairs water quality in the watershed. Impervious cover i...The urban environment has continued to experience changes from increasing impervious surfaces, which alters the proper functioning of the ecological zones and impairs water quality in the watershed. Impervious cover is predominantly used as an indicator to assist in understanding and forecasting the impact of human actions and other related activities on aquatic resources. In this study, the rate of change in land uses using the impervious surface as an indicator, and the percentage of imperviousness on the effect on water quality in the urban watershed were assessed. Ile-Ife was delineated as an urban watershed, and the percentage of imperviousness from 2008 to 2016 and the effect of imperviousness on water bodies were assessed. The study utilized ASTERDEM, Worldview (0.46 m), IKONOS (1.4 m), Landsat (30 m) for 2008 and 2016, GPS and Drone (10 cm). Water sampling was carried out in selected locations as generated by the impervious surface analyst tool, (ISAT). The percentage (%) of impervious surfaces accounted for 59.4% (4567.1/7691.5ha) in 2008 and 70.3% (5408.2/7691.5ha) in 2016, from the total number of lands investigated. The turbidity values from low to high regions were 32.3, 55.9 and 82.4 NUT. Changes in LULC of the watershed led to increased surface temperature, impermeable surfaces, and decreased vegetation, which exposes the area to flooding and reduced water quality. This study emphasized the importance of GIS and its integration into urban changes and water quality assessment.展开更多
This paper explores the potential to improve the impervious surface estimation accuracy using a multi-stage approach on the basis of vegetation-impervious surface-soil (V-I-S) model. In the first stage of Spectral Mix...This paper explores the potential to improve the impervious surface estimation accuracy using a multi-stage approach on the basis of vegetation-impervious surface-soil (V-I-S) model. In the first stage of Spectral Mixture Analysis (SMA) process, pixel purity index, a quantitative index for defining endmember quality, and a 3-dimensional endmember selection method were applied to refining endmembers. In the second stage, instead of obtaining impervious surface fraction by adding high and low albedo fractions directly, a linear regression model was built between impervious surface and high/low albedo using a random sampling method. The urban impervious surface distribution in the urban central area of Shanghai was predicted by the linear regression model. Estimation accuracy of spectral mixture analysis and impervious surface fraction were assessed using root mean square (RMS) and color aerial photography respectively. In comparison with three different research methods, this improved estimation method has a higher overall accuracy than traditional Linear Spectral Mixture Analysis (LSMA) method and the normalized SMA model both in root mean square error (RMSE) and standard error (SE). However, the model has a tendency to overestimate the impervious surface distribution.展开更多
The sub-pixel impervious surface percentage(SPIS) is the fraction of impervious surface area in one pixel,and it is an important indicator of urbanization.Using remote sensing data,the spatial distribution of SPIS val...The sub-pixel impervious surface percentage(SPIS) is the fraction of impervious surface area in one pixel,and it is an important indicator of urbanization.Using remote sensing data,the spatial distribution of SPIS values over large areas can be extracted,and these data are significant for studies of urban climate,environment and hydrology.To develop a stabilized,multi-temporal SPIS estimation method suitable for typical temperate semi-arid climate zones with distinct seasons,an optimal model for estimating SPIS values within Beijing Municipality was built that is based on the classification and regression tree(CART) algorithm.First,models with different input variables for SPIS estimation were built by integrating multi-source remote sensing data with other auxiliary data.The optimal model was selected through the analysis and comparison of the assessed accuracy of these models.Subsequently,multi-temporal SPIS mapping was carried out based on the optimal model.The results are as follows:1) multi-seasonal images and nighttime light(NTL) data are the optimal input variables for SPIS estimation within Beijing Municipality,where the intra-annual variability in vegetation is distinct.The different spectral characteristics in the cultivated land caused by the different farming characteristics and vegetation phenology can be detected by the multi-seasonal images effectively.NLT data can effectively reduce the misestimation caused by the spectral similarity between bare land and impervious surfaces.After testing,the SPIS modeling correlation coefficient(r) is approximately 0.86,the average error(AE) is approximately 12.8%,and the relative error(RE) is approximately 0.39.2) The SPIS results have been divided into areas with high-density impervious cover(70%–100%),medium-density impervious cover(40%–70%),low-density impervious cover(10%–40%) and natural cover(0%–10%).The SPIS model performed better in estimating values for high-density urban areas than other categories.3) Multi-temporal SPIS mapping(1991–2016) was conducted based on the optimized SPIS results for 2005.After testing,AE ranges from 12.7% to 15.2%,RE ranges from 0.39 to 0.46,and r ranges from 0.81 to 0.86.It is demonstrated that the proposed approach for estimating sub-pixel level impervious surface by integrating the CART algorithm and multi-source remote sensing data is feasible and suitable for multi-temporal SPIS mapping of areas with distinct intra-annual variability in vegetation.展开更多
Concerns regarding urbanization impacts on floods gradually moved from end-of-pipe solutions, based on open channel hydraulics improvement, to imperviousness ratio limiting and then to land use control and to integrat...Concerns regarding urbanization impacts on floods gradually moved from end-of-pipe solutions, based on open channel hydraulics improvement, to imperviousness ratio limiting and then to land use control and to integrated planning at local and large scale levels. The Niushou River basin is one of the fastest urbanizing areas in Nanjing City, East China, however, the high urban land percentage has leaded to series of flooding events. The paper aims to reveal the impact of imperviousness ratio, patterns and drainage system on flooding areas based on the unit of catchment and Storm Water Management Model(SWMM). The following conclusions were reached. 1) The ratio or spatial characteristics of the impervious surface affected the runoff volumes and associated floods areas. Despite the well-established drainage system, the high imperviousness ratio, particularly clustered pattern in locations such as hydrological sensitive zones aggravated the flooding tension across the basin. 2) The poor drainage hydraulic efficiency in local areas, and the lack of integral processes of infiltration, yield, storage and discharge in local catchment and larger basin are also significant factors. 3) The Niushou River basin development should improve the drainage transformations from a single local, short-term drainage process into integral, elastic processes of infiltration, yield, storage, and discharge.展开更多
The change of impervious surface area(ISA) can effectively reveal the gradual process of urbanization and act as a key index for monitoring urban expansion. Experiencing rapid growth of the built environment in the 20...The change of impervious surface area(ISA) can effectively reveal the gradual process of urbanization and act as a key index for monitoring urban expansion. Experiencing rapid growth of the built environment in the 2000 s, urban expansion of Beijing has not been fully characterized through ISA. In this study, Landsat TM images of Beijing in 2001 and 2009 were obtained, and the eight-year urban expansion process in Beijing was analyzed using the ISA extracted by means of the vegetation-imperious surface-soil(V-I-S) model. From the spatial variation in ISA, the ring structure of urban expansion in Beijing was significant during the study period, with decreasing urban density from the city center to the periphery. In the ring road analysis, the most dramatic changes of ISA were found between the fifth ring and the sixth ring. This area has experienced the most new residential development, and is currently the main source of urban expansion. The typical profile lines revealed the directional characteristics of urban expansion. The east-west profile was the most urbanized axes in Beijing, while ISA change in the east-north profile was more significant than in the other five profiles. Moreover, the transition matrix of ISA levels revealed an increase in urban density in the low density built areas; the Moran′s I index showed a clear expansion of the central urban area, which spread contiguously; and the standard deviational ellipse indicated the northeast was the dominant direction of urban expansion. These findings can provide important spatial control guidelines in the next round of national economic and social development planning, overall urban and rural planning, and land use planning.展开更多
In recent decades, Urban Heat Island Effects have become more pronounced and more widely examined. Despite great technological advances, our current societies still experience great spatial disparity in urban forest a...In recent decades, Urban Heat Island Effects have become more pronounced and more widely examined. Despite great technological advances, our current societies still experience great spatial disparity in urban forest access. Urban Heat Island Effects are measurable phenomenon that are being experienced by the world’s most urbanized areas, including increased summer high temperatures and lower evapotranspiration from having impervious surfaces instead of vegetation and trees. Tree canopy cover is our natural mitigation tool that absorbs sunlight for photosynthesis, protects humans from incoming radiation, and releases cooling moisture into the air. Unfortunately, urban areas typically have low levels of vegetation. Vulnerable urban communities are lower-income areas of inner cities with less access to heat protection like air conditioners. This study uses mean evapotranspiration levels to assess the variability of urban heat island effects across the state of Tennessee. Results show that increased developed land surface cover in Tennessee creates measurable changes in atmospheric evapotranspiration. As a result, the mean evapotranspiration levels in areas with less tree vegetation are significantly lower than the surrounding forested areas. Central areas of urban cities in Tennessee had lower mean evapotranspiration recordings than surrounding areas with less development. This work demonstrates the need for increased tree canopy coverage.展开更多
The mapping of impervious surface area(ISA) and urban green space(UGS) is essential for improving the urban environmental quality toward ecological, livable, and sustainable goals. Currently, accurate ISA and UGS prod...The mapping of impervious surface area(ISA) and urban green space(UGS) is essential for improving the urban environmental quality toward ecological, livable, and sustainable goals. Currently, accurate ISA and UGS products are lacking in urban areas at the global scale. This study established regression models that estimated the fraction of ISA/UGS in global 30 cities for validation using MODIS NDVI and DMSP/OLS nighttime light imageries. A global dataset of ISA and UGS fraction with a spatial resolution of 250 m×250 m was developed using the regression model, with a mean relative error of 0.19 for its ISA. The results showed the global urban area of 76.29×10~4 km^2, which was primarily distributed in central Europe, eastern Asia,and central and eastern North America. The urban land area in North America, Europe, and Asia was 66.3×10~4 km^2, accounting for 86.91% of the world’s urban area;the urban land area of the top 50 countries accounted for 59.32% of the total urban land area in the world. The global ISA of 45.26×10~4 km^2 was mainly distributed in central and southern North America, eastern Asia, and Europe, as well as coastal regions around the world. The proportion of ISA situated in built-up areas on the continental scale followed the order of Africa(>70%)>South America>Oceania>Asia(>60%)>North America>Europe(>50%), and these areas were mostly in southeastern North America, southwestern Europe, and eastern and western Asia. North America, Europe, and Asia accounted for 89.44% of the world’s total UGS. The cities of developed countries in Europe and North America exposed a dramatic mosaic of ISA and UGS composites in urban construction. Therefore, the proportion of UGS is relatively high in those cities. However, in developing and underdeveloped countries, the proportion of UGS in built-up areas is relatively low, and urban environments need to be improved for livability.展开更多
Extraction of impervious surfaces is one of the necessary processes in urban change detection.This paper derived a unified conceptual model (UCM) from the vegetation-impervious surface-soil (VIS) model to make the ext...Extraction of impervious surfaces is one of the necessary processes in urban change detection.This paper derived a unified conceptual model (UCM) from the vegetation-impervious surface-soil (VIS) model to make the extraction more effective and accurate.UCM uses the decision tree algorithm with indices of spectrum and texture,etc.In this model,we found both dependent and independent indices for multi-source satellite imagery according to their similarity and dissimilarity.The purpose of the indices is to remove the other land-use and land-cover types (e.g.,vegetation and soil) from the imagery,and delineate the impervious surfaces as the result.UCM has the same steps conducted by decision tree algorithm.The Landsat-5 TM image (30 m) and the Satellite Probatoire d’Observation de la Terre (SPOT-4) image (20 m) from Chaoyang District (Beijing) in 2007 were used in this paper.The results show that the overall accuracy in Landsat-5 TM image is 88%,while 86.75% in SPOT-4 image.It is an appropriate method to meet the demand of urban change detection.展开更多
Rainwater and run-off from three kinds of impervious surface in the Shanghai urban area,China were sampled.Polycyclic aromatic hydrocarbons(PAHs) were measured in the samples,and their sources were assessed.The mean s...Rainwater and run-off from three kinds of impervious surface in the Shanghai urban area,China were sampled.Polycyclic aromatic hydrocarbons(PAHs) were measured in the samples,and their sources were assessed.The mean sum of the 16 PAH concentrations measured in rainwater and run-offs from ceramic tiles,asphalt roofs,and asphalt roads were 873,1404,1743,and 4023 ng/L,respectively.The PAH concentrations found in this study were moderate compared to PAH concentrations found in run-offs in other studies.The main PAH components in the rainwater,roof run-off,and asphalt road run-off samples were 3-ring PAHs,3–4-ring PAHs,and 4–6-ring PAHs,respectively.Source apportionment results indicated that combustion(47.4%–55.5%) and vehicular emissions(30.5%–33.0%) were the major contributors to PAHs in roof run-off.Vehicular emissions were the most significant contributors to asphalt road run-off(47.2%),followed by combustion(23.5%),and petroleum(16.3%).Vehicular emissions and coal and natural gas combustion are therefore the most significant sources of PAHs in run-off from impervious surfaces in the Shanghai urban area.展开更多
Impervious surface area(ISA)is an important parameter for many environmental or socioeconomic relevant studies.The unique characteristics of remote sensing data made it the primary data source for ISA mapping at vario...Impervious surface area(ISA)is an important parameter for many environmental or socioeconomic relevant studies.The unique characteristics of remote sensing data made it the primary data source for ISA mapping at various scales.This paper summarizes general ISA mapping procedure and major techniques and discusses impacts of scale issues on selection of remote sensing data and corresponding algorithms.Previous studies have indicated that ISA mapping remains a challenge,especially in urban–rural frontiers and in covering a large area.Effectively employing rich spatial information in high spatial resolution imagery through texture and objectbased methods is valuable.Data fusion of multi-resolution images and spectral mixture analysis are common approaches to reduce the mixed pixel problem in medium spatial resolution images such as Landsat.Coarse spatial resolution images such as MODIS and DMSP-OLS are valuable for national and global ISA mapping but more research is needed to effectively integrate multisource/scale data for improving mapping performance.Development of an optimal procedure corresponding to specific study areas and purposes is required to generate accurate ISA mapping results.展开更多
Many efforts have been devoted to extracting impervious surfaces based on different methods from multiple spatial resolution images.Differences in extraction methods and spatial resolutions are significant and have le...Many efforts have been devoted to extracting impervious surfaces based on different methods from multiple spatial resolution images.Differences in extraction methods and spatial resolutions are significant and have led to discrepant performances in terms of the impervious surface extraction accuracy.However,which extraction method is more suitable for which kind of spatial resolution image in practice is poorly understood.This study systematically compared the performances of 12 methods of impervious surface extraction for four spatial resolution images(i.e.Landsat 8[30 m],Sentinel-2A[20 m],Sentinel-2A[10 m],and Gaofen-2[4 m])in three testing areas.The results indicated that for the mediumspatial resolutions of 30 and 20 m,the support vector machine(SVM)method was considered as the optimal classification method with the highest accuracy of impervious surface extraction.For the high-spatial resolutions of 10 and 4 m,the object based image analysis(OBIA)method obtained the highest accuracy of the impervious surface distribution.Furthermore,the perpendicular impervious surface index(PISI)outperformed the other indices in obtaining the impervious surface distribution,with the highest accuracy for four spatial resolution images.These comprehensive assessments can provide a valuable guidance for future impervious surface extraction from different spatial resolutions.展开更多
文摘Hydrologic modeling is a popular tool for estimating the hydrological response of a watershed. However, modeling processes are becoming more complex due to land-use changes such as urbanization, industrialization, and the expansion of agricultural activities. The primary goal of the research was to use the HEC-HMS model to evaluate the impact of impervious soil layers and the increase in rainfall-runoff processes on hydrologic processes. For these purposes, the Watershed Modelling System (WMS) and Hydrologic Engineering Center’s-Hydrologic Modeling System (HEC-HMS) models were used in this study to simulate the rainfall-runoff process. To compute runoff rate, runoff volume, base flow, and flow routing methods SCS curve number, SCS unit hydrograph, recession, and loss routing methods were selected for the research, respectively. To reduce the processing time and computational complexity, a small section of the Pipestem Creek Watershed was selected to understand the methods and concepts associated with the hydrologic simulation model building. A DEM along with other required data such as land use land cover data, soil type data, and meteorological data was utilized to delineate the watershed in WMS. The output of WMS was utilized to run the HEC-HMS model for five different scenario analyses. All the relevant data were plugged in to the model to get the desired map. Subsequently, outlets at appropriate locations were selected for the sub-basin delineation for further analysis. Finally, the model was parametrized to get successful simulation results. Overall, peak discharges and runoff volumes were increased with increasing storm depths and impervious areas. Peak discharges were increased to 36% and 51% when rainfall depths were increased by 10% and 20% from the initial rainfall depth, respectively. Runoff volumes were also increased to 35% and 49% for the same scenarios, respectively. Peak discharges were increased to 12% and 78% with a 10% and 20%, respectively, increase in impervious areas. The runoff volumes were increased by 12% and 76% when impervious areas were increased by 10% and 20%, respectively. The simulation models responded well, and the peak discharges and runoff volumes increased with increasing storm depths and impervious areas.
基金Under the auspices of the National Social Science Foundation of China(No.16BJY039)
文摘The urban heat island(UHI) effect has significant effects on the quality of life and public health. Numerous studies have addressed the relationship between UHI and the increase in urban impervious surface area(ISA), but few of them have considered the impact of the spatial configuration of ISA on UHI. Land surface temperature(LST) may be affected not only by urban land cover, but also by neighboring land cover. The aim of this research was to investigate the effects of the abundance and spatial association of ISAs on LST. Taking Harbin City, China as an example, the impact of ISA spatial association on LST measurements was examined. The abundance of ISAs and the LST measurements were derived from Landsat Thematic Mapper(TM) imagery of 2000 and 2010, and the spatial association patterns of ISAs were calculated using the local Moran’s I index. The impacts of ISA abundance and spatial association on LST were examined using correlation analysis. The results suggested that LST has significant positive associations with both ISA abundance and the Moran’s I index of ISAs, indicating that both the abundance and spatial clustering of ISAs contribute to elevated values of LST. It was also found that LST is positively associated with clustering of high-ISA-percentage areas(i.e.,>50%) and negatively associated with clustering of low-ISA-percentage areas(i.e.,<25%). The results suggest that, in addition to the abundance of ISAs,their spatial association has a significant effect on UHIs.
基金The financial support from National Natural Science Foundation of China (Grant Nos. 12172211 and 52078021)Shanghai Key Laboratory of Rail Infrastructure Durability and System Safety, China (Grant No. R201904)
文摘This study focuses on the consolidation behavior and mathematical interpretation of partially-saturated ground improved by impervious column inclusion.The constitutive relations for soil skeleton,pore air and pore water for partially saturated soils are proposed in the context of partially-saturated ground improved by impervious column inclusion.Settlement equation and dissipation equations of excess pore air/water pressures for a partially saturated improved ground are then derived.The semi-analytical solutions for ground settlement and pore pressure dissipation are then obtained through the Laplace transform and validated by the existing solutions for two special cases in the literature and the numerical results obtained from the finite difference method.A series of parametric studies is finally conducted to investigate the influence of some key factors on consolidation of partially saturated ground improved by impervious column inclusion.Based on the parametric study,it can be found that a higher value of the area replacement ratio or modulus of the pile results in a longer dissipation time of excess pore air pressure(PAP),a shorter dissipation time of excess pore water pressure(PWP),and a lower normalized settlement.
文摘The province of British Columbia, Canada, has established an Agricultural Land Reserve (ALR) to protect the most suitable soil landscapes for agriculture. Increases in population and urbanization have resulted in development challenges on ALR lands. The Metro Vancouver area is the most productive agricultural area in British Columbia as well as the most rapidly growing urban region. The increase in impervious areas has decreased the amount of arable land for soil-based agriculture and altered the hydrological cycle. Analysis using a combination of aerial imagery and GIS found that impervious areas comprise about 10 percent of the ALR within Metro Vancouver. Farm residences and greenhouses have the largest effect on reducing the soil surface for water infiltration. This decrease in area has negatively influenced the ecosystem heath of the region, as well as, decreasing the amount of agricultural land for soil based agriculture and both surface and groundwater dynamics.
基金This work was financially supported by the National Natural Science Foundation of China (Ratification No.59479029)
文摘This paper investigates the performance of geomembrane composites used as impervious andheat-insulating lining within a breakwater for a power station.The seepage field,distribution ofstress-strain contour and seepage discharge of hot water which has been treated as the inner thermalsource in the calculation of heat-insulation,have been given by three-dimensional calculation method coup-ling seepage with stress.The results indicate that the impervious and heat-insulation effect ofgeomembrane composites is significant.
文摘Asset management is a strategic decision-making aspect of social infra-structure that ensures safety by predicting long-term conditions and maximizing effectiveness under budgetary constraints. Predicting the deterioration of impervious walls is essential in the asset management of coastal landfill sites, particularly in the design of their maintenance and repair strategy. In this paper, a quantitative evaluation of the leakage of toxic substances in coastal landfill sites where deterioration of side impervious walls has decreased the water interception performance is reported. In addition, risk evaluation based on the asset management of the leakage is applied to determine an appropriate repair method. The strategy of repairing the walls when the concentration of the toxic substances leaking into the sea area exceeds the closure and abandonment of coastal landfill sites is demonstrated to be superior. Moreover, the strategy of repairing only the seaside side impervious wall is shown to be cost-effective.
文摘The urban environment has continued to experience changes from increasing impervious surfaces, which alters the proper functioning of the ecological zones and impairs water quality in the watershed. Impervious cover is predominantly used as an indicator to assist in understanding and forecasting the impact of human actions and other related activities on aquatic resources. In this study, the rate of change in land uses using the impervious surface as an indicator, and the percentage of imperviousness on the effect on water quality in the urban watershed were assessed. Ile-Ife was delineated as an urban watershed, and the percentage of imperviousness from 2008 to 2016 and the effect of imperviousness on water bodies were assessed. The study utilized ASTERDEM, Worldview (0.46 m), IKONOS (1.4 m), Landsat (30 m) for 2008 and 2016, GPS and Drone (10 cm). Water sampling was carried out in selected locations as generated by the impervious surface analyst tool, (ISAT). The percentage (%) of impervious surfaces accounted for 59.4% (4567.1/7691.5ha) in 2008 and 70.3% (5408.2/7691.5ha) in 2016, from the total number of lands investigated. The turbidity values from low to high regions were 32.3, 55.9 and 82.4 NUT. Changes in LULC of the watershed led to increased surface temperature, impermeable surfaces, and decreased vegetation, which exposes the area to flooding and reduced water quality. This study emphasized the importance of GIS and its integration into urban changes and water quality assessment.
基金Under the auspices of National Natural Science Foundation of China (No. 40701177)
文摘This paper explores the potential to improve the impervious surface estimation accuracy using a multi-stage approach on the basis of vegetation-impervious surface-soil (V-I-S) model. In the first stage of Spectral Mixture Analysis (SMA) process, pixel purity index, a quantitative index for defining endmember quality, and a 3-dimensional endmember selection method were applied to refining endmembers. In the second stage, instead of obtaining impervious surface fraction by adding high and low albedo fractions directly, a linear regression model was built between impervious surface and high/low albedo using a random sampling method. The urban impervious surface distribution in the urban central area of Shanghai was predicted by the linear regression model. Estimation accuracy of spectral mixture analysis and impervious surface fraction were assessed using root mean square (RMS) and color aerial photography respectively. In comparison with three different research methods, this improved estimation method has a higher overall accuracy than traditional Linear Spectral Mixture Analysis (LSMA) method and the normalized SMA model both in root mean square error (RMSE) and standard error (SE). However, the model has a tendency to overestimate the impervious surface distribution.
基金Under the auspices of National Natural Science Foundation of China(No.41671339)
文摘The sub-pixel impervious surface percentage(SPIS) is the fraction of impervious surface area in one pixel,and it is an important indicator of urbanization.Using remote sensing data,the spatial distribution of SPIS values over large areas can be extracted,and these data are significant for studies of urban climate,environment and hydrology.To develop a stabilized,multi-temporal SPIS estimation method suitable for typical temperate semi-arid climate zones with distinct seasons,an optimal model for estimating SPIS values within Beijing Municipality was built that is based on the classification and regression tree(CART) algorithm.First,models with different input variables for SPIS estimation were built by integrating multi-source remote sensing data with other auxiliary data.The optimal model was selected through the analysis and comparison of the assessed accuracy of these models.Subsequently,multi-temporal SPIS mapping was carried out based on the optimal model.The results are as follows:1) multi-seasonal images and nighttime light(NTL) data are the optimal input variables for SPIS estimation within Beijing Municipality,where the intra-annual variability in vegetation is distinct.The different spectral characteristics in the cultivated land caused by the different farming characteristics and vegetation phenology can be detected by the multi-seasonal images effectively.NLT data can effectively reduce the misestimation caused by the spectral similarity between bare land and impervious surfaces.After testing,the SPIS modeling correlation coefficient(r) is approximately 0.86,the average error(AE) is approximately 12.8%,and the relative error(RE) is approximately 0.39.2) The SPIS results have been divided into areas with high-density impervious cover(70%–100%),medium-density impervious cover(40%–70%),low-density impervious cover(10%–40%) and natural cover(0%–10%).The SPIS model performed better in estimating values for high-density urban areas than other categories.3) Multi-temporal SPIS mapping(1991–2016) was conducted based on the optimized SPIS results for 2005.After testing,AE ranges from 12.7% to 15.2%,RE ranges from 0.39 to 0.46,and r ranges from 0.81 to 0.86.It is demonstrated that the proposed approach for estimating sub-pixel level impervious surface by integrating the CART algorithm and multi-source remote sensing data is feasible and suitable for multi-temporal SPIS mapping of areas with distinct intra-annual variability in vegetation.
基金Under the auspices of National Natural Science Foundation of China(No.41171429,41571511)
文摘Concerns regarding urbanization impacts on floods gradually moved from end-of-pipe solutions, based on open channel hydraulics improvement, to imperviousness ratio limiting and then to land use control and to integrated planning at local and large scale levels. The Niushou River basin is one of the fastest urbanizing areas in Nanjing City, East China, however, the high urban land percentage has leaded to series of flooding events. The paper aims to reveal the impact of imperviousness ratio, patterns and drainage system on flooding areas based on the unit of catchment and Storm Water Management Model(SWMM). The following conclusions were reached. 1) The ratio or spatial characteristics of the impervious surface affected the runoff volumes and associated floods areas. Despite the well-established drainage system, the high imperviousness ratio, particularly clustered pattern in locations such as hydrological sensitive zones aggravated the flooding tension across the basin. 2) The poor drainage hydraulic efficiency in local areas, and the lack of integral processes of infiltration, yield, storage and discharge in local catchment and larger basin are also significant factors. 3) The Niushou River basin development should improve the drainage transformations from a single local, short-term drainage process into integral, elastic processes of infiltration, yield, storage, and discharge.
基金Under the auspices of Key Project of National Natural Science Foundation of China(No.41130534)
文摘The change of impervious surface area(ISA) can effectively reveal the gradual process of urbanization and act as a key index for monitoring urban expansion. Experiencing rapid growth of the built environment in the 2000 s, urban expansion of Beijing has not been fully characterized through ISA. In this study, Landsat TM images of Beijing in 2001 and 2009 were obtained, and the eight-year urban expansion process in Beijing was analyzed using the ISA extracted by means of the vegetation-imperious surface-soil(V-I-S) model. From the spatial variation in ISA, the ring structure of urban expansion in Beijing was significant during the study period, with decreasing urban density from the city center to the periphery. In the ring road analysis, the most dramatic changes of ISA were found between the fifth ring and the sixth ring. This area has experienced the most new residential development, and is currently the main source of urban expansion. The typical profile lines revealed the directional characteristics of urban expansion. The east-west profile was the most urbanized axes in Beijing, while ISA change in the east-north profile was more significant than in the other five profiles. Moreover, the transition matrix of ISA levels revealed an increase in urban density in the low density built areas; the Moran′s I index showed a clear expansion of the central urban area, which spread contiguously; and the standard deviational ellipse indicated the northeast was the dominant direction of urban expansion. These findings can provide important spatial control guidelines in the next round of national economic and social development planning, overall urban and rural planning, and land use planning.
文摘In recent decades, Urban Heat Island Effects have become more pronounced and more widely examined. Despite great technological advances, our current societies still experience great spatial disparity in urban forest access. Urban Heat Island Effects are measurable phenomenon that are being experienced by the world’s most urbanized areas, including increased summer high temperatures and lower evapotranspiration from having impervious surfaces instead of vegetation and trees. Tree canopy cover is our natural mitigation tool that absorbs sunlight for photosynthesis, protects humans from incoming radiation, and releases cooling moisture into the air. Unfortunately, urban areas typically have low levels of vegetation. Vulnerable urban communities are lower-income areas of inner cities with less access to heat protection like air conditioners. This study uses mean evapotranspiration levels to assess the variability of urban heat island effects across the state of Tennessee. Results show that increased developed land surface cover in Tennessee creates measurable changes in atmospheric evapotranspiration. As a result, the mean evapotranspiration levels in areas with less tree vegetation are significantly lower than the surrounding forested areas. Central areas of urban cities in Tennessee had lower mean evapotranspiration recordings than surrounding areas with less development. This work demonstrates the need for increased tree canopy coverage.
基金supported by the Major Projects of the National Natural Science Foundation of China(Grant No.41590842)the Strategic Priority Research Program of the Chinese Academy of Sciences,Pan-Third Pole Environment Study for a Green Silk Road(Pan-TPE)(Grant No.XDA20040400)the National High Technology Research and Development Program of China(Grant No.2013AA122802)
文摘The mapping of impervious surface area(ISA) and urban green space(UGS) is essential for improving the urban environmental quality toward ecological, livable, and sustainable goals. Currently, accurate ISA and UGS products are lacking in urban areas at the global scale. This study established regression models that estimated the fraction of ISA/UGS in global 30 cities for validation using MODIS NDVI and DMSP/OLS nighttime light imageries. A global dataset of ISA and UGS fraction with a spatial resolution of 250 m×250 m was developed using the regression model, with a mean relative error of 0.19 for its ISA. The results showed the global urban area of 76.29×10~4 km^2, which was primarily distributed in central Europe, eastern Asia,and central and eastern North America. The urban land area in North America, Europe, and Asia was 66.3×10~4 km^2, accounting for 86.91% of the world’s urban area;the urban land area of the top 50 countries accounted for 59.32% of the total urban land area in the world. The global ISA of 45.26×10~4 km^2 was mainly distributed in central and southern North America, eastern Asia, and Europe, as well as coastal regions around the world. The proportion of ISA situated in built-up areas on the continental scale followed the order of Africa(>70%)>South America>Oceania>Asia(>60%)>North America>Europe(>50%), and these areas were mostly in southeastern North America, southwestern Europe, and eastern and western Asia. North America, Europe, and Asia accounted for 89.44% of the world’s total UGS. The cities of developed countries in Europe and North America exposed a dramatic mosaic of ISA and UGS composites in urban construction. Therefore, the proportion of UGS is relatively high in those cities. However, in developing and underdeveloped countries, the proportion of UGS in built-up areas is relatively low, and urban environments need to be improved for livability.
基金supported by the National Natural Science Foundation of China (Grant No.40671127)the National Hi-Tech Research and Development Program of China ("863" Project) (Grant Nos.2006AA120101,2006AA120102)+1 种基金the National Key Technology Research and Development Program (Grant No.2008BAK49B04)the National China Next General Internet Program (Grant No.CNGI–09–01–07)
文摘Extraction of impervious surfaces is one of the necessary processes in urban change detection.This paper derived a unified conceptual model (UCM) from the vegetation-impervious surface-soil (VIS) model to make the extraction more effective and accurate.UCM uses the decision tree algorithm with indices of spectrum and texture,etc.In this model,we found both dependent and independent indices for multi-source satellite imagery according to their similarity and dissimilarity.The purpose of the indices is to remove the other land-use and land-cover types (e.g.,vegetation and soil) from the imagery,and delineate the impervious surfaces as the result.UCM has the same steps conducted by decision tree algorithm.The Landsat-5 TM image (30 m) and the Satellite Probatoire d’Observation de la Terre (SPOT-4) image (20 m) from Chaoyang District (Beijing) in 2007 were used in this paper.The results show that the overall accuracy in Landsat-5 TM image is 88%,while 86.75% in SPOT-4 image.It is an appropriate method to meet the demand of urban change detection.
基金supported by the National Key Technology R&D Program of China(No.2010BAK69B16-1)the Shanghai Commission of Science and Technology(No.10dz1200402),China
文摘Rainwater and run-off from three kinds of impervious surface in the Shanghai urban area,China were sampled.Polycyclic aromatic hydrocarbons(PAHs) were measured in the samples,and their sources were assessed.The mean sum of the 16 PAH concentrations measured in rainwater and run-offs from ceramic tiles,asphalt roofs,and asphalt roads were 873,1404,1743,and 4023 ng/L,respectively.The PAH concentrations found in this study were moderate compared to PAH concentrations found in run-offs in other studies.The main PAH components in the rainwater,roof run-off,and asphalt road run-off samples were 3-ring PAHs,3–4-ring PAHs,and 4–6-ring PAHs,respectively.Source apportionment results indicated that combustion(47.4%–55.5%) and vehicular emissions(30.5%–33.0%) were the major contributors to PAHs in roof run-off.Vehicular emissions were the most significant contributors to asphalt road run-off(47.2%),followed by combustion(23.5%),and petroleum(16.3%).Vehicular emissions and coal and natural gas combustion are therefore the most significant sources of PAHs in run-off from impervious surfaces in the Shanghai urban area.
基金The authors acknowledge supports from the Zhejiang A&F University’s Research and Development Fund-talent startup project(2013FR052)Zhejiang Provincial Key Laboratory of Carbon Cycling in Forest Ecosystems and Carbon Sequestration,School of Environmental and Resource Sciences,Zhejiang A&F University and Center for Global Change and Earth Observations,Michigan State University.
文摘Impervious surface area(ISA)is an important parameter for many environmental or socioeconomic relevant studies.The unique characteristics of remote sensing data made it the primary data source for ISA mapping at various scales.This paper summarizes general ISA mapping procedure and major techniques and discusses impacts of scale issues on selection of remote sensing data and corresponding algorithms.Previous studies have indicated that ISA mapping remains a challenge,especially in urban–rural frontiers and in covering a large area.Effectively employing rich spatial information in high spatial resolution imagery through texture and objectbased methods is valuable.Data fusion of multi-resolution images and spectral mixture analysis are common approaches to reduce the mixed pixel problem in medium spatial resolution images such as Landsat.Coarse spatial resolution images such as MODIS and DMSP-OLS are valuable for national and global ISA mapping but more research is needed to effectively integrate multisource/scale data for improving mapping performance.Development of an optimal procedure corresponding to specific study areas and purposes is required to generate accurate ISA mapping results.
基金sponsored in part by the National Natural Science Foundation of China[grant numbers 41201432,41901347]Guangdong Basic and Applied Basic Research Foundation[grant number 2021A1515011411,2020A1515010562].
文摘Many efforts have been devoted to extracting impervious surfaces based on different methods from multiple spatial resolution images.Differences in extraction methods and spatial resolutions are significant and have led to discrepant performances in terms of the impervious surface extraction accuracy.However,which extraction method is more suitable for which kind of spatial resolution image in practice is poorly understood.This study systematically compared the performances of 12 methods of impervious surface extraction for four spatial resolution images(i.e.Landsat 8[30 m],Sentinel-2A[20 m],Sentinel-2A[10 m],and Gaofen-2[4 m])in three testing areas.The results indicated that for the mediumspatial resolutions of 30 and 20 m,the support vector machine(SVM)method was considered as the optimal classification method with the highest accuracy of impervious surface extraction.For the high-spatial resolutions of 10 and 4 m,the object based image analysis(OBIA)method obtained the highest accuracy of the impervious surface distribution.Furthermore,the perpendicular impervious surface index(PISI)outperformed the other indices in obtaining the impervious surface distribution,with the highest accuracy for four spatial resolution images.These comprehensive assessments can provide a valuable guidance for future impervious surface extraction from different spatial resolutions.
