The Study On Evaluation And Optimization Of Urban Green Space Based On 3S Technology

As an organic component of urban ecosystem,green space plays an important role in improving urban ecological environment,elevating people's living standard as well as creating ecological livable city.With the boost of urbanization progress,Urban land increasingly tense,and the space for urban greening is on the decrease,thus the problem of how to give full play to all functions of green space,and achieve sustainable development of city within the limitation of land source in a city,through reasonable planning and layout of urban green space system,remains to be urgent tackled.The establishment of the evaluation system of green space is the premise and basis of the reasonable construction of urban green space system.At present,urban planning and construction departments use the method of statistical estimation or artificial estimation,which have some limitations for the objective and accurate evaluation for green space system.This thesis took landscape ecology theory and suitability assessment theory as instructions,built a information database for urban green space with SPOT image supported by 3S technology and quantitative analysis method.Based on this,comprehensive quantitative evaluation for structure and functions of urban green space was established,and the suitability evaluation was carried out.Furthermore,the index evaluation system and the suitability evaluation mentioned above were used to comprehensive assess the green space construction of Haikou city,and some optimization strategy were also put forward for the green space construction,striving to enrich and complete the comprehensive evaluation system for urban green space,as well as the theory and method system for ecological planning of urban landscape under the support of 3S technology.The main research contents are as below:(1)Analysis on urban green space structure based on classification of green spaceTaking Haikou City as the object of study,the thesis,with the assist of 2010's SPOT remote image and ARCGIS,established information database of urban green space by selecting the central urban area for research scope;which enhance the convenience of data collection and accuracy of data statistics.Based on the database,this thesis discussed the spatial structure of green space under different classification,by classifying the urban green space in the aspects of functions,patches scale and shape.The composition and the spatial structure of urban green space can be understood from different aspects.The results showed:the overall structure of urban green space within central urban area in Haikou was not reasonable,the distribution was unbalanced,and the system was imperfect.In addition,there existed a fair gap between administrative regions.For instance:Longhua district was unreasonable in constitution and spatial structure of green space;Meilan district was inadequate in park green space and serious in fragmentation of green space;Qiongshan district lacked green space for corridor and park;Xiuying district was unbalanced in the distribution of park green space.(2)Comprehensive quantitative evaluation for structure and functions of urban green spaceAfter looking up the literature and files,74 indexes using frequently were screened out by adopting principal component analysis and consulting experts,21 evaluation indexes were finally confirmed.Exploiting AHP to determine the weight of indexes,we built comprehensive quantitative evaluation for structure and functions of urban green space including four first grade indexes:basic quantity character of green space,the structure,the functions and the landscape;and 21 secondary indexes.The evaluation index values were calculated based on the urban green space information database,so that the evaluation system can be applied to different cities,the administrative regions or the specific range,and the evaluation result could be more scientific,the work cold be more efficient.Taking Haikou as a case,we evaluated the construction level of green space in central urban area,showing that the composite score was 0.6,it was in II level based on the comprehensive assessment standard for urban green space.It showed that the overall construction of green space was better,but still had a large space for optimization.Among which,the highest score was 0.76 for landscape,basic quantity character was 0.61,structure and functions of green space were 0.58 and 0.52.Those displayed that the green space of central urban area in Haikou was good enough in overall construction;gave full play to green space landscape,and was good in landscape quality and effect;and reasonable in structure and layout;but plain in greenbelt ecology and social functions.(3)Analysis on suitability of urban greenbelt based on suitability assessment theoryWe established suitability evaluation model by selecting 10 suitability factors remarkably affecting the building of green space such as slope,elevation,soil,tropical island effect,population density,transportation distribution and rivers and lakes,etc.,and adopting AHP to confirm the weight of factor.After that,classified the suitability of each factor and assigned them.It showed that the higher the assignment was,the more sensitive or more weak the ecological environment was,and the building of green space was more urgent,thus the suitability of green space would be higher.On the basis of this,we obtained distribution grade for urban green space suitability,through weighted overlay analysis of multiple factors.We evaluated the suitability of green space,analyzed and classified the land within the research area on the foothold of green space suitability,to decide the direction of urban green space layout,which could play a key guiding role for scientific and rational layout of urban green space.Taking Haikou as a case,it showed that within the central urban area of Haikou,unavailable area accounted for 30.2%,unsuitable area accounted for 20.6%,basically suitable area took 29.1%,suitable area was 14.7%,and the most suitable land accounted for 5.4%,among which,the suitable area for green space mainly lay in the periphery of waters,industry zone in the south of Xiuying district and urban expanding area in the south of Qiongshan district.(4)Strategy of optimization for Haikou green spaceOn the basis of previous studies,we analyzed comprehensive evaluation results for structure and functions of urban green space and urban green space suitability layout collaboratively,to make optimization of urban green space based on comprehensive evaluation of current status and analysis on land suitability,and applied to the optimization of green space in Haikou.This thesis put forward the optimization strategy from the aspects of urban park system,green corridor,group green space,wedge green space and tree species.Practice showed that 3S technology and suitability assessment theory in the urban green space system planning application have provided an effective mode and way for the scientific selection of urban green space,and made up the deficiency of the traditional planning theories and methods of green space system.