Green Roof Planning In High-density Urban Areas

The high density of population and buildings and their concentration in large cities are the main characteristics of urbanization in Asia,making large cities in some Asian countries,including China,have higher densities and more compact layouts than Europe and the US.China’s high-density urban areas are mainly concentrated in economically developed city-intensive areas such as the Yangtze River Delta,the Pearl River Delta,Beijing-Tianjin-Hebei and other urban agglomerations,which collect nearly 78%of the country’s population and create more than 80%of GDP.However,high-density construction has effectively curbed urban sprawl while also generating a series of social and environmental problems,including missing green network,significant heat island effect and severe waterlogging,which seriously endanger human health.How to minimize negative impact on built environment in high-density urban areas has become an urgent task to promote urban transformation in direction of resilience and sustainability.Green roofs,as a green technology for ecological restoration and landscape reconstruction,is an effective way to efficiently utilize stock space,solve contradiction between ecological construction and land scarcity,and improve quality of built environment.Therefore,scientific research on green roof planning in high-density urban areas is important to ameliorate problems associated with urban densification and to promote sustainable development.At present,researches related to green roofs are mainly focused on neighborhoods,buildings and other meso and micro scales,and there is a lack of urban macro scale research.With the innovative development of earth observation technologies such as high-definition remote sensing and information extraction technologies such as machine learning,it has become possible to obtain information quickly and precisely to conduct urban-scale green roof research.In this context,this thesis proposes that the key issues of urban green roof planning are lack of systematic research on green roofs,the planning paradigm to be innovated(methodological issues),lack of accurate assessment of planning,and urgent breakthrough in large-scale quantitative characterization(technical issues),lagging compilation of green roof planning,and the policy system to be improved(policy issues).In view of this,the thesis attempts to solve the key issues by developing a planning system combining technical and policy rationality based on the theoretical paradigm of ecol-rational planning in the new era,combined with the application of intelligent technologies such as high-resolution remote sensing and machine learning.In summary,the goal of this thesis is to construct a green roof planning method in urban high-density areas under the guidance of the concept of eco-rational planning in the new era,propose a technical system for urban green roof planning and supplement it with a reasonable policy system for green roof promotion,so as to provide technical and policy support to guarantee scientific compilation and implementation of green roof planning in urban high-density areas.In terms of the technology,taking Xiamen Island,a typical urban high-density area as the study area,this thesis integrates the whole process planning technical system of"potential assessment-planning implementation-benefit assessment".(1)Potential assessment-assessment of green roof constructability of existing buildings:based on multi-source data including geographic information data and remote sensing images(database construction),combined with planning zoning and building classification elements,the index system of green roof constructability is constructed and quantitatively calculated through machine learning,remote sensing,Arc GIS and other technical methods(index quantification),and TOPSIS-MCS coupling model is used to assess green roof constructability of existing building(constructability assessment).(2)Planning implementation-green network space optimization and strategy development:combined with the grading of green roof constructability and urban ground green space,the short and long-term greening scenarios are set,the MSPA and MCR models are used to construct the green network under different greening scenarios,and the implementation strategies are developmented by integrating division of key implemention zoning,guidelines for greening grading and classification of building greening.(3)Benefit assessment-quantitative assessment of cooling effect of green roofs:using Landsat 8 remote sensing image data in the summers of two years before and after the implementation of green roofs in study area,the single window algorithm is used to retrieve the surface temperature,and 3S technology is used to quantitatively portray the cooling effect of urban green roofs.In terms of the policy,based on international experience and local development,the policy system framework for the promotion of urban green roofs in suitable areas in China is constructed combined with the administrative classification and development stage.Following the above-mentioned study,the concluding remarks include:(1)The"mapping(data extraction)-fusion(index calculation)-relation(spatial optimization)"methodological framework for green roof planning in high-density urban areas,constructed by the eco-rational planning paradigm in the new era,provides scientific guidance of conceptual ideas,logical thinking and methodological tools for green roof planning.(2)The whole process planning technical system of"potential assessment-planning implementation-benefit assessment"breaks through key technologies such as intelligent extraction of rooftop elements,quantitative calculation of correlation indexes and construction of collaborative decision-making models,which can achieve scientific,accurate and practical planning of green roofs in high-density urban areas.1)"Potential assessment"ensures the rationality of green roof planning.The total area of green roofs in Xiamen Island is 54 hm~2,and 70.4%of ungreened roofs are suitable for greening,of which 10.3%and 17.6%of all suitable roofs are grade 1 and 2 respectively.2)"Planning implementation"enhances the implementability of green roof planning.With the increase in implementation of green roofs,the landscape connectivity of Xiamen Island’s green network has been significantly enhanced and the network structure has been improved.3)"Benefit assessment"guarantees the sustainability of green roof implementation.Urban-scale green roofs have a significant cooling effect.The average land surface temperature difference between green roof areas and Xiamen Island is reduced by 0.91℃ because of urban green roofs and the cooling effect of green roofs is significant within a radius of 100 m.(3)The policy framework for green roofs in China,which combines administrative classification and development stages of green roof promotion,promotes the effective implementation of technical system and guides sustainable development of urban green roofs.This thesis is innovative in following aspects:(1)A method framework of"mapping(data extraction)-fusion(index calculation)-relation(spatial optimization)"is proposed for green roof planning in high-density urban areas based on the concept of eco-rational planning.(2)Based on multiple technology platforms such as Arc GIS,RS,machine learning,a whole process technology system of green roof planning with multi-disciplinary integration,multi-data processing,multi-index calculation and multi-model integration is build.(3)A framework of policy system for green roofs in China is systematically proposed combining technical and policy rationality.The findings of this thesis have made positive exploration for responding to rational transformation of urban planning,implementing ecological civilization construction,as well as provide technical support and decision-making reference for the scientific compilation and implementation of urban green roof planning.