| A city is an important place where demographic, economic, social, cultural and other factors are highly concentrated, it has the characteristics of high density cluster development, especially the high density of the population concentration. With the acceleration of urbanization and the rapid expansion of cities, there has accumulated a large amount of urban safety problems. High level of urbanization means the scale of the city expands obvioulsy, the number of cities increases highly, and open space areas shrink greatly. Besides, the acceleration of urbanization produces a range of urban problems, such as the population is supersaturated, urban green space is decreasing, architectural space is congested, and the ecological environment is deteriorating. At the same time, it becomes the catalyst for urban disasters, and expands the loss of disasters. Therefore, how to promote urban safety development will become one of the major issues faced by urban development in the future.Urban disaster prevention green space is the important component of refuge place. It is the first refuge choice of residents. Researches about the layout status, optimal site selection and it's effect evaluation of urban disaster prevention green space are the foundation of urban disaster prevention system, and urban disaster prevention and mitigation planning, and the important point of the theoretical and practical study on urban safety development. With the acceleration of urbanization in China, economic development has always been a hot issue, however, urban safety development has often been overlooked. There still has not enough concern about urban safety planning among all aspect of urban planning, and the enforcement is still too weak. Besides, the urban safety system is still insufficient, and the safety installations and their guarantee level is relatively low.This study focuses on the base of urban safety development, disaster prevention system construction, and urban disaster prevention and mitigation planning, discussing the layout status of disaster prevention green space, optimal site selection, and it's effects evaluation in central urban area of Shenyang systematically through the unique research ideas and methods of geography. Major contents of this article are as follows:Part ? (Chapter 1 and chapter 2):discussing research background, regional overviews, research methods, data sources and processing, research ideas and processing, research objectives and significance, and research progress.Part ? (Chapter 3, chapter 4 and chapter 5):systematically analyzing the layout status of disaster prevention green space in central urban area of Shenyang. Firstly, the layout status of disaster prevention green space is measured by it's own attributes. Disaster prevention green space attributes are described through overlap and coverage rate of service domain areas, the supply and demand ratio, the emergency response capability of disaster prevention green space, and the road network densities within the service domain areas. The spatial accessibility based on the spatial relationship between disaster prevention green space and street network are calculated by betweenness centrality. And the degree of fragmentation is measured by landscape continuity research methods. Under the foundation of the spatial accessibility achieved above, this study takes the population-transportation-disaster prevention green space as a whole system, and measures the street network betweenness centrality according to MCA, and the matching degree between the population, disaster prevention green space, and the street network betweenness centrality.Part ? (Chapter 6):because of the deficiencies of the existing researches, this article firstly constructs thematic maps according to different location factors that affect the site selection of disaster prevention green space. Secondly, by raster data overlay analysis methods, measuring the suitability of site selection. Lastly, according to the optimal location principles of disaster prevention green space, filterring out the best suitable location of disaster prevention green space among the sites that are suitable for site selection. Besides, the effect of the disaster prevention green space after the optimal site selection is evaluated in Chapter 7.Main conclusions made by this research are as follows:1) Layout status of the disaster prevention green space in central urban area of Shenyang.Judging from the attributes of disaster prevention green space itself, the distribution of the disaster prevention green space is uneven. Firstly, overlap rates of the disaster prevention green space service domain areas are high, and the coverage rates are relatively low, especially in densely populated area, where the coverage rates are generally lower. Secondly, the relationship between disaster prevention green space and basic services infrastructure is estranged, and matching degree is poor, which means the emergency response capability of disaster prevention green space is low. Thirdly, the road network densities within the service domain areas are low, especially the service domain areas of large disaster prevention green space, however, the urban center, where the road network density is high, the disaster prevention green space is fewer and smaller in size.The spatial accessibility of disaster prevention green space, which decline from urban center to the edge of the city, has 8 large high value distribution areas. These areas, where the disaster prevention green space are distributed, have greater network nodes' controllability in case of congestion of network traffic, and play more important role and have greater influence in the entire street network. Besides, the disaster prevention green space that distribute in these places have more shortest paths connecting every two nodes of the street network, and better traffic efficiency, and thus better accessibility. The disaster prevention green space in the north part of the urban edge and the urban center that have higher average accessible population, and the disaster prevention green space in the urban edge that have larger scale and longer average accessible time all have worse accessibility, which means that the areas where the disaster prevention green space above distributed have less shortest path connecting every two nodes of the street network, and lower traffic efficiency.The continuity of disaster prevention green space is relatively low, and the degree of fragmentation is high. There are a large number of independent patches, and the linkage between them is low. Only when the distance threshold goes up to 4600 meters, the continuity gradually grows slightly higher, and the fragmentation degree decreases accordingly. Judging from the local continuity analysis results, the large disaster prevention green space patches in the urban peripheral play an important role in the process of continuity maintaining. With the increase of the distance threshold, the importance of smaller patches begins to increase, but still much lower than larger disaster prevention green space patches.2) The effect evaluation of disaster prevention green space site selection.Judging from the attributes of the disaster prevention green space itself, there is a more obvious improvement after optimal site selection. Firstly, the overlap rates of the disaster prevention green space services domain areas have greatly reduced, and the coverage rates have substantially improved, and the distribution is more uniform. This will helpful to reduce the waste of disaster prevention resources, and improve their efficiency. Secondly, after the optimal site selection, the statistical indicators about supply and demand ratio indicate the distribution supply and demand ratio is better than the existing disaster prevention green space. This greatly eases the problem of supply over demand and demand over supply. Disaster prevention green space tend to be evenly distributed, and the residents have equal opportunities to get access, the compatibility between disaster prevention green space and population distribution is enhanced. Thirdly, the enhancement of the compatibility between disaster prevention green space and basic service infrastructure is better suited to help improve the emergency response capability of the disaster prevention green space. Lastly, the road network densities within the services domain ares of the disaster prevention green space has improved, and the numbers of the disaster prevention green space, which has high road network densities within their services domain ares, has increased greatly.From the perspective of the spatial relationship between the disaster prevention green space and the street network, the spatial accessibility of the disaster prevention green space has improved greatly too. The spatial accessibility layout of disaster prevention green space becomes more rational and even, the difference between spatial accessibility layout of disaster prevention green space of the urban edge and the urban center becomes smaller. And the average accessible time is shorter, and the average accessible population becomes larger totally. The disaster prevention green space matches better with population. Besides, scale of the disaster prevention green space has improved overally, and distribute more evenly.The continuity of disaster prevention green space increased, and the degree of fragmentation decreased after the site selection. This will inprove the efficiency of disaster evacuation, mitigates the stress of transportation infrastructure caused by evacuation processes, and prevent the occurrence of further anthropogenic secondary disasters. The distribution of the disaster prevention green space patches' importance is more even, and the polarization degree is eased. |
PDF Full Text Request