摘要:为推动城市公园绿地应急避险体系建设的发展，在评价指标体系的指导下，应用GIS的空间插值技术，对北京城市人口统计数据进行了空间分布化，并通过人口密度分布与公园绿地缓冲区的叠加分析，对城市公园绿地的人口服务辐射能力进行了探索研究。结果显示，整个北京规划市区内公园绿地的缓冲区覆盖范围总计为421.96km2，约占规划市区面积的38%，存在626.46km2的服务盲区。另外，规划市区东部、北部和西南最外围区域大多数办事处中所含的公园绿地缓冲区占其行政区面积的比例均低于10％。在分析基础上，还进行了公园绿地应急避险功能布局的设想。

　　Abstract:In order to promote the urban park development for emergency and disaster-prevention functions, the urban population spatial distribution is carried out with the guidance of the evaluation index system and the application of the GIS spatial interpol methods, and the population service radiation capability of urban park green space is studied through the superposition analysis of the population density distribution and the park buffer zones. The results show that the total area of park buffer zone in Beijing city proper is 421.96km2, 38% of the total urban planning area, while the uncovered service space is 626.46km2. In addition, most of the park buffer zones in furthest periphery of the east, north and southwest parts of the planning area are less than 10 percent of their administrative area. Finally the layout of emergency and disaster-prevention functions of park green space are proposed on the basis of the analysis.

　　文章部分内容:

4 北京城市公园绿地应急避险功能布局的设想

　　4.1 基本目标和原则

　　在保证城市绿地发挥其景观、生态功能的同时，为了保护人民生命财产的安全，实现构筑布局合理、不同服务半径层次基本覆盖，居民能快速到达一个避险场所的城市公园绿地应急避险功能体系的目标。

　　在综合考虑各方面因素的基础上，即结合北京地理自然条件(西北部为西山的延伸部分；东南部为平原地区，以农业用地和农田作物为主，宜林绿地面积大，便于城市绿化发展)、现有绿化现状、楔形绿地规划、水系分布、山体分布因素，在推动城市绿地建设的发展过程中，根据以人为本、科学性、可操作性、就近和系统性原则进行布局设想。

　　4.2 城市公园绿地应急避险功能布局的设想

　　为配合2008奥运会，2005年北京已制定《北京中心城地震及其他灾害应急避难场所(室外)规划纲要》，逐步将八大城区的一些公园绿地改造为配有应急避险设施的真正意义上的避灾疏散场地，目前北京中心城已建成与公园绿地有关的24处应急避险场所[8]。

　　在本布局设想中，根据城市园林绿化现状、功能及规划原则，在保持《北京市区绿地系统规划》(2002年)的基本结构基础上，结合城市公园绿地的人口服务辐射能力分析以及现已建成的应急避险场所，主要采用“绿环、多中心点、多通道”的公园绿地网络拓扑结构进行布局设想，具体为：

　　(1)“绿环”，即由环绕城市的二环、三环、四环和五环路两侧绿化形成多个绿环(图6)，两侧的带状绿地各划定不低于道路红线宽度，与其他道路主干道形成交叉节点，形成拓扑结构和缓冲地段，遇到意外灾情可尽快疏散城市人口，保证城市居民安全。

　　(2)“多中心点”，即根据现有公园绿地的地理位置、规模(不含水体)和功能等属性，选择性地作为应急避险的救护中心，并将面积在50hm2以上的非公园绿地规划为应急避险的救护中心。最终，通过分析比较，考虑到城中心(指四环之内区域)已建成了分布相对密集的应急避险场所，从城市的发展和均衡的角度，偏重于郊区和卫星城区域，共选择了23处绿地建议作为应急避险的救护中心，其中包括13处面积在50hm2以上的非公园绿地，和10处面积在30hm2以上的公园绿地。

　　(3)“多通道”，即包括长安街、南北中轴道路、主干道及两侧的带状绿地，形成似玫瑰图形的放射形疏散主通道网，将救护中心、躲避空间联系起来(图6)。

　　另外，从(图6)所对应的服务半径分析可以得出，所布局设想的绿地500m服务半径缓冲区覆盖范围基本可以覆盖郊区的西南和东南区域(限于篇幅，相关图表不在此列出)，东北区域可结合楔形绿地，从易于管理的角度，宜以公园为主的改造建设形式，进行改造或增加新的绿地。

　　The Layout Study on the Emergency and Disaster-prevention Functions of the Green Space of Beijing City Parks

　　XIE Jun-fei, LI Yan-ming, LI Shu-hua

　　1 Preface

　　In urban green space system, urban parks, with wide space, perfect facilities, low density of building, can provide excellent emergency shelter condition. Due to learn more emergency and disaster-prevention functions of urban green space system, Chinese government began to pay more attention to the green space construction with emergency and disaster-prevention functions. But, at present, studies mostly focused on qualitative description, it needs quantitative spatial assessment in-depth, and needs to know how to perfect the planning of urban emergency adapting system within urban whole layout frame, and how to raise park population radiation capability.

　　In this study, to present a optimization proposal for the layout on emergency and disaster-prevention functions system of urban park in Beijing, according to evaluation index system, spatial distribution of Beijing population statistical data was done with spatial interpolation methods of Geography Information System (GIS), meanwhile, based on dot, line, side entity in vector database, the analysis on buffer zone with different radius around parks were carried out, finally, the relevant problems about population service radiation capability of park were studied, based on the maps overlap of population density distributing and buffer zone of park.

　　2 Study area and data

　　In this study, the study region was determined according to Beijing urban planning boundary, and was shown in Figure 2, in which total area is 1 097km2, the objectives of this research are park green spaces(excluding its water region)in the study region, the basic vector data of park green space all obtained from Beijing urban green space investigate database in 2005, which were provided by Beijing Municipal Bureau of Parks. All the data layer were registered to the same Beijing local coordinates system and resampled to the same pixel resolution of 0.6 m.

　　3 Actual status analysis on population service radiation capability of parks in Beijing urban planning

　　3.1 Spatial distribution of population statistical data based on GIS

　　In order to accomplish spatial distribution of population, The first step is to scatter GIS vector element detail consisted of 125 street offices. The second step is to collect the total population data within 125 street offices(based on 2005 green space general investigation document), finally, spatial distribution of population statistical data based on GIS was done with the Kernel estimation method.

　　Figure 1 showed that the population density was biggest in center urban region, there is a descending trend for population density from center to urban suburb, which was coincidence with the actual population distributing condition. The estimated population density in gridding region was mostly consistent with statistic value. The estimated population density in urban planning extension was 5 000 per square kilometer.

　　3.2 Buffer zone analysis on urban park

　　In the present study, in order to identify parks influence on its external environment, based on operation between buffer-zone analysis and union module of Arc view software, a certain exterior buffer zone was extracted by 1 500 m, 1 000 m and 500 m service radius around park (excluding parks itself). Table 1 and Figure 2 showed the buffer-zone cover 421.96 km2, the cover area account for 38% of the total planned urban area (the overlapped parts of buffer zone had been resolved). Another, there be 626.46 km2 which was unable to access emergency shelter service, which was neither belong to park nor belong to the buffer zone.

　　Taking street office as the basic administrative units to be accounted, the buffer zone in the eastern, northern, southwestern street offices of the urban suburb accounted for less than 10%, the buffer zone of most street offices in the sub-regional accounted for less than 25%. With economic development, the new large-scale communities are constantly emerging, in order to provide equal opportunities of choice and sound hedging space in dealing with natural disasters and other emergencies, it is necessary to undertake a green space layout from the perspective of emergency shelter.

　　In the central city, the data showed that the coveraged area about buffer zone amount to 70.25 km2, with another 16.39 km2 of areas unable to access emergency shelter service. The buffer zone of Xicheng district covered the largest area of 25.21 km2, which constitutes 79.35% of the overall administrative area, followed by Xuanwu district, which constitutes 78.42% of the overall administrative area.

　　3.3 Analysis of the population service radiation capability of urban park

　　Based on the grid maps overlap of buffer zone and distribution map of population density in urban planning area, finally, the results were obtained that population density of the buffer zone was 10 586 per square kilometers, if multiplied by 421.96 km2 of buffer zone, the population within the coverage of the service were 4.47 million. Considering altogether 7.02 million population registered in the city, there were still more than 2.55 million of people had no access to the emergency shelter service.

　　Theoretically, according to demand that everyone has 2 m2 green space at emergency shelters, if the park with 5 000 hm2 all was rebuilded emergency shelters under the hypothesis condition, there only were 4.47 million of people which had access to the emergency shelter service within service radius. But, every park is not only single purpose for emergency shelters, but also they should afford more complex function in fact.

　　4 The design of park layout on emergency and disaster-prevention functions system in Beijing urban planning

　　As part of the preparation for 2008 Olympics, Beijing developed the "Beijing Downtown Earthquake and Disasters Emergent Shelter (Outdoors) Program" in 2005. The program designed some parks and green spaces in eight districts in downtown Beijing as real disasters shelters with emergency facilities. By now there have been constructed 24 emergency shelters in urban areas.

　　In current study, the design was developed according to the present plant coverage, function and development guidelines. It was based on the basic structure of the "System Layout of Beijing Urban Green Lands"(2002) with consideration of population absorbing capabilities of parks and the existing emergency shelters. The design consisted of a topology network of parks with "green belts, multi-hubs and multi-passages".

　　(1)Green belts: there were belts of plant covered areas along the 2nd, 3rd, 4th and 5th ring roads of Beijing. The green belts on both sides of the roads were not less narrow than the road red lines, and formed a network of buffer zone with pathways to other main roads for evacuation of populations in case of emergent disasters.

　　(2)Multi-hubs: emergency rescue and aid hubs were carefully selected based on the geographic locations, size (excluding water areas), functions of present parks et al., Green spaces (not parks) with lands over 50 hm2 were designed as the emergency rescue and aid hubs. In the program, we recommended 23 green spaces in suburb and satellite towns around the city to be constructed as emergency rescue and aid hubs, including 13 green spaces (not parks) with over 50 hm2 of area and 10 parks with over 30 hm2 of area.

　　(3)Multi-passages: passages included Chang'an Street, center-axis road connecting north and south, main roads and green space on both sides of these roads. These passages formed a actinomorphic network of evacuation passages that connect rescue hubs and shelters together.

　　In addition, the buffer region as shown in Figure 5 can cover most areas including southwestern and southeastern suburb with 500 m service radius around the green space. Northeastern region can be covered with reconstruction of present wedgy green space or new green space. It was recommended that the reconstruction be done based on present parks for easier management.

　　5 Conclusions and perspectives

　　From this study, the following major conclusions could be drawn:

　　(1)In the urban planning area in Beijing, buffer zone of park total was 421.96 km2, accounted for 38% areas of the overall program, with another 626.46 km2 of areas unable to access service.

　　(2)With in the planned areas, the average population desity for buffer zone was 10 586 people per square kilometers. If multiplied by 421.96 km2 of buffer zone, the population within the coverage of the service were 4.47 million. Considering altogether 7.02 million population registered in the city, there were still more than 2.55 million of people have

　　no access to the emergency shelter service.

　　(3)Based on future growth and balance of the city, 23 pieces of green spaces in suburb and satellite towns were recommended as emergent rescue and aid hubs, with main roads in the city connecting them together as a network of evacuation.

　　Aim of key problems of urban park emergency, the paper mainly discussed the methodologies and technical ways of emergency rescue and shelter in city areas. More precise conclusions can be achieved based on more detailed information of population distributions.

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　　作者简介:谢军飞/1976年生/男/湖南人/硕士/工程师/北京市园林科学研究所/研究方向为城市生态评价(北京 100102)

　　李延明/1965年生/男/教授级高级工程师/北京市园林科学研究所(北京 100102)

　　李树华/男/博士/教授/中国农业大学观赏园艺与园林学系(北京 100094)