The Defensible Space Study And Evaluated That Based On The AHP Of Chengdu Huanhuaxi Park

As the city’s open space, City Park providing a platform for people to getting close to and understanding the nature,meanwhile it’s an important place for people to strengthen exchanges and enrich lives. With the development of society, social negative emotions increasing, the incidence of crime and insecurity in city park is also increasing, which not only reduces the defensibility of park’s space environment, but also bring people with a sense of insecurity.This article from the most basic security needs and the space users’perspective, throughing objective and effective evaluation methods to evaluate and explorate the defensible space of Huanhuaxi Park. According to the diversity and complexity of environmental in city park, this paper chooses AHP, data envelopment analysis and weighted sum approach to evaluate Huanhuaxi park. Using AHP to build indicator system of urban parks defensible space evaluation.Through screening and optimization,we can determine each indicator of the indicator system.At last, inviting experts to determine the index weight and build the ultimate indicator system. Using the completed indicator system to design questionnaires and release to visitors. Through the evaluation and research of Huanhuaxi park Defensible Space, several conclusions can be established as follows:(1) Putting forward the method of city park defensible space evaluation. In this paper, AHP, data envelopment analysis and linear weighted evaluation method have been used to evaluate Defensible space of Huanhuaxi Park. Using AHP and DEA to build indicator system of urban parks defensible space evaluation, and then, using linear weighted evaluation method to evaluate Defensible space of Huanhuaxi Park. Practice has proved that the method which was has been chosen is reasonable.(2) Constructing the indicator system of city park defensible space evaluation. Since there is no previous experience, indicator system in this paper has its innovative and has proved itself by rationality and practicality. On the basis of Newman’s defensible space theory and considering the characteristics of city park,this paper established the evaluation indicator system of city park Defensible Space which is composed of the target layer, criteria layer and index layer. The indicator system consists of 4 layers and 17 indicators.(3) The influence to defensibility of each index can be quite different. The weight proportion of natural surveillance in guidelines layer is nearly 50% and has the greatest influence to defensibility, while the environment atmosphere and environment impression have minimum impact on defensibility.In indicator layer,the sight patency and lighting conditions have the highest weight value and the greatest influence to defensibility;the constitute of visitors and health status have the minimum weight value and the minimum effects on defensibility. In the later defensible space design and improvement,designer shall meet the more important indicator, and then consider the second important indicator.(4) The overall situation of defensibility in Huanhuaxi Park is generally good. Through the defensible space evaluation of Huanhuaxi park, we can see that comprehensive evaluation value of the overall evaluation of Huanhuaxi park is 6.64, the evaluation result is good. Huanhuaxi park has a beautiful environment and a high value of health, beautiful degree, comfort and cohesion.So,Huanhauxi park has a good condition of defensibility and a good ambience.(5) Four partitions’s situation of defensibility is generally good, but the difference is large. From the evaluation results, we can see that the four partition’s defensibility is generally good, but the evaluation results of the egret island is not good and poetry avenue evaluation results is outsdanding, so the gap between the four partitions becomes large. Trees hill and canglang lake have a good evaluation results and their quality and defensibility of space are in good condition. Poetry Avenue has a good defensibility status and it’s comprehensive evaluation value is the highest in Huanhuaxi park. Poetry avenue has a good unobstructed line of sight, it can attract many visitors to stop and stay a long time and gathere a lot of popularity. May be the defensibility of egret island is relatively weak. Egret Island has a large plant density and it’s road is very bend, what’s more, the less land area of makes it gathere less popularity. Therefore, it’s defensibility is weak.(6) Huanhuaxi park has its advantages in terms of defense, but also has its shortcomings. Overall, the advantage factors as follows:health status, beautiful degree, the healthy of tourist activities, comfort and cohesion; the shortcomings as follows:sight patency, lighting conditions, privacy of space, leisure and entertainment facilities.