Effectively evaluating the effects of urban forms on CO2 emissions has become a hot topic in socioeconomic sustainable development; however, few studies have been able to explore the urban form-CO2 ...emission relationships from a multi-perspective view. Here, we attempted to analyze the relationships between urban forms and CO2 emissions in 264 Chinese cities, with explicit consideration of the government policies, urban area size, population size, and economic structure. First, urban forms were calculated using the urban land derived from multiple-source remote sensing data. Second, we collected and processed CO2 emissions and three control variables. Finally, a correlation analysis was implemented to explore whether and to what extent the spatial patterns of urban forms were associated with CO2 emissions. The results show that urban form irregularity had a more significant impact on CO2 emissions in low-carbon pilot cities than in non-pilot cities. The impact of the complexity of urban forms on CO2 emissions was relatively significant in the small- and large-sized cities than in the medium-sized cities. Moreover, urban form complexity had a significant correlation with CO2 emissions in all of the cities, the level of which basically increased with the population size. This study provides scientific bases for use in policy-making to prepare effective policies for developing a low-carbon economy with consideration of the associations between urban forms and CO2 emissions in different scenarios.
•Urban form connectivity could help to reduce CO2 emissions at the national scale.•Urban form connectivity had the most significant impact on CO2 emissions in large-sized cities.•Urban form complexity had a significant impact on CO2 emissions in the low-carbon pilot cities.•Only urban form irregularity had a positive impact on CO2 emissions in the service cities.•There was a significant difference in the urban form-CO2 emission relationships among cities of various population sizes.
Outdoor thermal comfort in urban spaces is known as an important contributor to pedestrians' health. The urban microclimate is also important more generally through its influence on urban air quality ...and the energy use of buildings. These issues are likely to become more acute as increased urbanisation and climate change exacerbate the urban heat island effect. Careful urban planning, however, may be able to provide for cooler urban environments. Different urban forms provide different microclimates with different comfort situations for pedestrians. In this paper, singular East–West and North–South, linear East–West and North–South, and a courtyard form were analysed for the hottest day so far in the temperate climate of the Netherlands (19th June 2000 with the maximum 33 °C air temperature). ENVI-met was used for simulating outdoor air temperature, mean radiant temperature, wind speed and relative humidity whereas RayMan was used for converting these data into Physiological Equivalent Temperature (PET). The models with different compactness provided different thermal environments. The results demonstrate that duration of direct sun and mean radiant temperature, which are influenced by urban form, play the most important role in thermal comfort. This paper also shows that the courtyard provides the most comfortable microclimate in the Netherlands in June compared to the other studied urban forms. The results are validated through a field measurement and calibration.
•Outdoor thermal comfort of singular, linear and courtyard forms are studied in a summer day.•The Singular shape receives the longest and the courtyard the shortest direct sun.•Averages of Ta and Tmr are the lowest for the courtyard.•The courtyard provides 81% comfortable hours while the others less than 38%.
•The overview of existing work on smart (and) sustainable cities is comprehensive, thorough, topical, and original.•Several critical issues remain unsettled, less explored, largely ignored, and ...theoretically underdeveloped for applied purposes.•Numerous research opportunities are available and worth exploring, as the field of smart sustainable cities is still in its early stages of development.•One opportunity of high relevance and importance is to develop a theoretically and practically convincing model of smart sustainable urban form or a framework for strategic smart sustainable urban development.•This holistic approach is believed to be the first of its kind and hence has not been, to the best of one’s knowledge, produced elsewhere.
In recent years, the concept of smart sustainable cities has come to the fore. And it is rapidly gaining momentum and worldwide attention as a promising response to the challenge of urban sustainability. This pertains particularly to ecologically and technologically advanced nations. This paper provides a comprehensive overview of the field of smart (and) sustainable cities in terms of its underlying foundations and assumptions, state–of–the art research and development, research opportunities and horizons, emerging scientific and technological trends, and future planning practices. As to the design strategy, the paper reviews existing sustainable city models and smart city approaches. Their strengths and weaknesses are discussed with particular emphasis being placed on the extent to which the former contributes to the goals of sustainable development and whether the latter incorporates these goals. To identify the related challenges, those models and approaches are evaluated and compared against each other in line with the notion of sustainability. The gaps in the research within the field of smart sustainable cities are identified in accordance with and beyond the research being proposed. As a result, an integrated approach is proposed based on an applied theoretical perspective to align the existing problems and solutions identification for future practices in the area of smart sustainable urban planning and development. As to the findings, the paper shows that critical issues remain unsettled, less explored, largely ignored, and theoretically underdeveloped for applied purposes concerning existing models of sustainable urban form as to their contribution to sustainability, among other things. It also reveals that numerous research opportunities are available and can be realized in the realm of smart sustainable cities. Our perspective on the topic in this regard is to develop a theoretically and practically convincing model of smart sustainable city or a framework for strategic smart sustainable urban development. This model or framework aims to address the key limitations, uncertainties, paradoxes, and fallacies pertaining to existing models of sustainable urban form—with support of ICT of the new wave of computing and the underlying big data and context–aware computing technologies and their advanced applications. We conclude that the applied theoretical inquiry into smart sustainable cities of the future is deemed of high pertinence and importance—given that the research in the field is still in its early stages, and that the subject matter draws upon contemporary and influential theories with practical applications. The comprehensive overview of and critique on existing work on smart (and) sustainable cities provide a valuable and seminal reference for researchers and practitioners in related research communities and the necessary material to inform these communities of the latest developments in the area of smart sustainable urban planning and development. In addition, the proposed holistic approach is believed to be the first of its kind. That is, it has not been, to the best of one’s knowledge, investigated or produced elsewhere.
In recent decades, the pedestrian's outdoor thermal comfort has been critical for designing sustainable cities, which can be affected by wind flow in urban spaces. Urban forms influence wind speed, ...changing the urban air quality, and causing pedestrians' thermal comfort or discomfort. Therefore, it is required to design the urban spaces in such a way as to regulate the wind speed in order to provide thermal comfort situations for pedestrians based on their climate conditions. This study aimed to provide a framework for analysing the outdoor thermal comfort of various building layouts and their relation to wind speed in a site. This paper also proposed new indexes for improvements to the Physiological Equivalent Temperature (PET) index enabling the calculation of outdoor thermal comfort based on the likelihood of people being outside for a whole day. In-situ measurements were carried out in Tehran, Iran, to validate the presented framework. Simulations were conducted for 15 critical points in nine different building layouts for the windiest day on the site. ENVI-met was used to simulate the wind speed, outdoor air temperature, and mean radiant temperature, while PET was calculated by means of Leonardo and RayMan. The results demonstrated that pedestrians' outdoor thermal comfort for in-site and out-site points improved by 2.8% and 2.3%, respectively, compared to the current site situation. Also, the framework produced a suitable urban form to provide outdoor thermal comfort with evaluating different urban forms.
•A framework is introduced to quantify the outdoor thermal comfort of pedestrians.•The framework was able to produce an urban form to enhance outdoor thermal comfort.•Proposed a new daily assessment index based on PET.•The relation between pedestrians' outdoor thermal comfort and wind speed is assessed.
•Urban flooding is a growing problem, causing considerable harm to people and infrastructure.•An analysis of the influence of urban forms on the surface flow of urban flooding was conducted.•The ...results showed that in different scenarios, urban forms had some impact on urban flow.•However, the impact patterns were relatively complex.•The results could help flood-sensitive urban design and flood risk management practitioners.
Diversified urban forms resulting from urbanization is a pivotal factor influencing urban pluvial flooding. A systematic analysis of the influence of urban forms on the surface flow of urban pluvial flooding was conducted. We obtained 1,000 sets of 1 km × 1 km urban form data that met quality control requirements using a random slicing method, based on actual urban underlying surface data, with nine spatial characteristic parameters used to tabulate the urban forms. A two-dimensional hydrodynamic model was employed to simulate the surface flow of the urban flood inundation. Scenario simulations and analyses were conducted for three slopes (1, 2, and 3 %) and three rainfall scenarios (with return periods of 5, 20, and 100 yr). The results showcased that, in different scenarios, the urban forms had some impact on urban flow variables and their processes, although the impact patterns were relatively complex. Regarding the process of urban flow variables, the urban forms affected the rate of decline in flood variables during the descending stage. The correlation analysis highlighted that road density, road area proportion, spread contact among various patch types, and uniformity across patches have important impacts on the maximum flood volume and maximum inundated area. The research results could help deepen our understanding of the formation mechanisms of urban pluvial flooding, flood-sensitive urban design, and flood risk management.
Planning and development of urban is one of the key factors that affect CO2 emissions. Sustainable urban planning and development is crucial to achieving carbon neutrality. However, there are ...relatively less studies in quantifying the impacts of urban forms and socioeconomic development on CO2 emissions with considering its spatial autocorrelation effects at the city-level. Thus, this study aimed to analyze the impacts of urban forms and socioeconomic factors on CO2 emissions of cities in Guangdong province during 2000–2017 based on a spatial panel econometric model. The results showed that CO2 emissions of Guangdong province increased significantly with a growth rate of 151% and had obvious spatial clustering characteristics. Urban form and socioeconomic development had a significant impact on CO2 emissions. Specifically, the results indicated that increasing the continuity of urban areas and improving the traffic coupling factor can help reduce CO2 emissions. The economic growth, population increase and economic openness degree increase would lead to stronger CO2 emission. In addition, the spatial spillover effects would enhance such impacts of the driving factors. Specifically, when the spillover effect of spatial Dubin model was taken into account, every 1% increase in urban class area, mean perimeter-area ratio, GDP, population, technology level and urbanization rate would lead a total CO2 emissions change by −0.53%, 1.3%, 1.1%, 0.18%, 12% and 1.4%, respectively. The results suggested that cities in Guangdong province should develop a more compact pattern, urban development with a scattered or disperse pattern should transform towards one continuous core city cluster and city belt, thus enhancing integration and sharing of infrastructure and related policies for low carbon development.
Water-sensitive urban design is an integral part of flood risk management. Based on computational modelling, we investigated the influence of various urban forms on flooding severity at the level of ...an urban block and for the case of long-duration urban flooding. The upstream flow depths, downstream discharge partition and flow exchange through the urban forms were examined. The results indicate that one urban characteristic has an overwhelming influence on the flow variables: the conveyance porosity in the main flow direction is by far more influential than the conveyance porosity in the normal direction or the number of streets. Such anisotropic effect was not pointed in recent similar studies, and it hints at practical guidelines for sustainable urban planning in practice. Moreover, the computational model was verified against laboratory observations, which constitute a novel valuable dataset for the validation of other urban flooding models.
The rapid urbanization of China related to fine particulate (PM2.5) emissions has attracted global attention, and exploring how urban forms affect PM2.5 concentration has become a hot topic for ...sustainable development of cites. Here, we combined multisource data and econometric models to quantify the relationships between urban forms and PM2.5 concentration in 250 Chinese cities, with explicit consideration of urban area size, population size, economic structure, and geographical location. The results showed that urban expansion had significant positive impacts on PM2.5 concentration in medium-sized (50–150 km2) and very large-sized cities (>250 km2). Urban form compactness tended to be beneficial for the reduction in PM2.5 concentration in large cities (5 million < population < 10 million). The urban form-PM2.5 concentration relationships were also dominated by economic structure change. That is, urban form irregularity/compactness played an important role in PM2.5 concentration within second cities (the proportion of second industry > 50%) and other cities compared to third cities (the proportion of third industry > 50%). Moreover, a compact and connected urban form was found to be more beneficial for reducing PM2.5 emissions in the northern region than in other regions. This study illustrates that the urban form-PM2.5 concentration relationships are sensitive to the differences in urban types and suggests that flexible urban planning strategies can actually help to reduce PM2.5 concentration in Chinese cities.
To reduce carbon dioxide (CO2) emissions attributed widely to human activities, previous studies have paid great attention to the relationships between socioeconomic development, urban forms and CO2 ...emissions in cities, and provided relevant emission mitigation policies through the effective urban spatial planning. However, whether and how different features of urban forms (such as compactness) affecting the levels of CO2 emissions is still debatable, specifically considering the different development levels of the cities. Therefore, this study is to synthetically explore how socioeconomic factors and urban forms work together to affect CO2 emissions with the consideration of differences in development levels of five city tiers in China. First, CO2 emissions in each city were derived from provincial energy statistics, radiance-calibrated nighttime light imageries, and population distribution data based on a disaggregating model. Then, a set of variables representing socioeconomic factors and urban forms were acquired from the city statistics and land use data, respectively. After obtaining the balanced dataset of these five city tiers from 1995 to 2015, the panel data analysis was finally applied to evaluate the consequences of socioeconomic factors and urban forms on CO2 emissions under different development stages. The estimation results show that the economic development, population growth, and urban land expansion are important factors that accelerating CO2 emissions in all the city tiers. Besides, irregular or fragmented structures of urban land use could result in more CO2 emissions due to the increase in potential transportation requirements in all the city tiers. Notably, an increasing concentrated pattern in the urban core is found to increase CO2 emissions in the tier-one cities, but to promote the reduction of CO2 emissions in other four city tiers. The urban spatial development with a compact and multiple-nuclei pattern is suggested to be closely linked with a lower level of CO2 emissions. Such results highlight the importance of a city's development level for decision-making involving the mitigation of CO2 emissions, and provide scientific support for building a low-carbon city from the perspective of both socioeconomic development and urban spatial planning.
•Differentiated impacts of socioeconomic factors and urban forms on CO2 emissions are explored.•Socioeconomic growth and urban land expansion promote CO2 emissions in all city tiers.•Urban forms in different development levels have different impacts on CO2 emissions.•Fragmented patterns of urban land can result in more CO2 emissions in all city tiers.•Compact and centralized developments do little to reduce emissions in tier-one cities.
Urban forms at human-scale, i.e., urban environments that individuals can sense (e.g., sight, smell, and touch) in their daily lives, can provide unprecedented insights on a variety of applications, ...such as urban planning and environment auditing. The analysis of urban forms can help planners develop high-quality urban spaces through evidence-based design. However, such analysis is complex because of the involvement of spatial, multi-scale (i.e., city, region, and street), and multivariate (e.g., greenery and sky ratios) natures of urban forms. In addition, current methods either lack quantitative measurements or are limited to a small area. The primary contribution of this work is the design of StreetVizor, an interactive visual analytics system that helps planners leverage their domain knowledge in exploring human-scale urban forms based on street view images. Our system presents two-stage visual exploration: 1) an AOI Explorer for the visual comparison of spatial distributions and quantitative measurements in two areas-of-interest (AOIs) at city- and region-scales; 2) and a Street Explorer with a novel parallel coordinate plot for the exploration of the fine-grained details of the urban forms at the street-scale. We integrate visualization techniques with machine learning models to facilitate the detection of street view patterns. We illustrate the applicability of our approach with case studies on the real-world datasets of four cities, i.e., Hong Kong, Singapore, Greater London and New York City. Interviews with domain experts demonstrate the effectiveness of our system in facilitating various analytical tasks.
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