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黄弘:应急响应的延伸-灾后的可持续性城市设计
 2010年09月22日
来源:省政府办公厅
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  Extension of Emergency Response – Sustainable City Design after Disaster

  Hong HUANG

  Center for Public Safety Research, Tsinghua University, Beijing, China  

  Abstract

  An emergency management concept based on triangle theory of public safety is reviewed at first in the paper. The emergency, acceptor, and response and management linked by hazard elements constitute the concept. As parts of emergency management, emergency response and recovery are not two discrete activities, recovery process should be an integral part of the emergency response. New city design after disaster considering sustainability is an important part of recovery. The design is thought to be an extension of emergency response, and the approaches from a large scale view and a local scale view are shown here. The design should be considered from the beginning of the emergency response.  

  1. Introduction

  On May 12, 2008, 8 level earthquake occurred in Wenchuan. It caused 69142 death, 17551 missing, and direct economy loss was 8451 hundred million RMB. Two years are gone, great efforts have been done on the emergency response and recovery process which give us not only experiences but also lessons.

  After suffered many public accidents, China government recognized the importance of emergency response to public accidents and contributes great effort to promote emergency management. Response and recovery are not two discrete activities and the response and recovery phases do not occur sequentially. Recovery should be an integral part of the response from the very beginning, as actions taken at all times can influence the longer-term outcomes for communities. In this paper, a concept based on triangle theory of public safety will be introduced, then as an extension of emergency response, sustainable city design methods including from large and local scale view after disaster are shown.

  2. Triangle theory of public safety

  An emergency management concept based on the triangle theory of public safety was proposed by Fan (2009). The theory considers that the whole process of the emergency and its response includes three key aspects: the emergencies, the acceptors, and the response and management. The three aspects are linked by “hazard elements” with the forms of the matter, the energy, and the information. The emergency will be induced if the hazards elements reach a critical value or meet with some activators. For example, earthquake occurs when the crustal motion reaches a certain intension, i.e., energy reaches a critical value. Based on such ideas, the framework is symbolized as a Triangle shown in Fig.1. The emergency is defined by an event or situation which bring serious damages to human, environment and security, etc. Its occurrence, development, evolution mechanisms including the type, intension and time-and-space distribution characteristics should be studied in this aspect. The acceptors include human beings, substances (such as buildings, facilities, lifelines, etc), and operational social and economical systems exposed to the emergencies. The body and function damaged mechanism and mode from emergencies, and the incident chain effects should be studied in this aspect. The incident chain effects mean the secondary disasters induced by the destroys of acceptors. For example, fire is a secondary disaster of earthquake. And the response and management is to study the type, time, strength of human’s interventions to both of emergency and acceptor to prevent the emergencies, reduce the damages and break down the incident chain effects. It includes evaluation, preparedness, response and recovery etc.  

  Fig. 1 Triangle theory of public safety

   The triangle theory provides a good understanding of emergency management. The theory considers that the every aspect in the response and management links each other and have dynamics progresses. Failure management of any aspect will course serious influence. Just as has mentioned, response and recovery are not independent. Recovery should be started at the beginning of the response. As an important part of recovery – sustainable city design will be introduced in the following parts.

  3. Sustainable city design - from a large scale view

  General speaking, city design for recovery will start from a large scale view, i.e., a design from a city level. The design should be based on three elements: damaged situation, city level and characteristics of the region. The damaged situation may include the status of damaged infrastructures, open spaces, lifelines, the place of refuges, transportation, and the present conditions and will of refugees, etc. Ishikawa (2008) proposed a sustainable city recovery plan for Dujiangyan with consideration of the damaged situation, city level and characteristics of the region.. They set up three main concepts for the recovery plan.

  Concept 1: The recovery plan should encourage refugees and provide hopes for their future.

  Concept 2: To seek the compact city in order to sustain the 2000 years’ assets of Double World Heritage City

  Concept 3: To create the Ecological City as the ideal of the 21st Century   

  Fig. 2 Garden cities                Fig. 3 Ecological City in the

  (Ebenezer Howard, 1898)            recovery plan (Ishikawa, 2008)   

  Fig.4 The principals of recovery plan (Ishikawa, 2008)

  The famous “Garden Cities” model proposed by Sir. Ebenezer Howard in 1898 is shown in Fig.2. The model says that a central city surrounding by several garden cities to form a region. The idea is to reduce the central city size, lower population density in central cities, surrounding the central city by the suburban belt. The population can be settled in the suburban cities, and all of these areas are linked with efficient public transport system. This idea is good for the people who want to live in the suburban area, however, it leads to the declination of the centeral city. Ishikawa (2008) investigated Dujiangyan and found that the historical structure of water system had supported this region for 2000 years. Based on this, they proposed a new relation between city and country which is shown in Fig.3. The recovery plan of Dujiangyan may be based on this structure named “Ecological City”. Fig.4 shows the principals of the recovery plan, green, water and culture. The concept of open spaces for safety, green, water and culture make the new city sustainable and becomes an important part of the Dujianyan recovery plan.

  4. Sustainable urban design - from a small scale view

  After the design from a large scale view, the design will be reduced to detail city block area, for example, apartments, CBD areas, schools, etc. In this kind of detailed design, safety, environment, energy, landscape, transportation, etc, should be considered in detail for the sustainability, and another approach will be used. Here, for instance, the environment design based on computer numerical simulation will be introduced here.

  With the increasing progress of computer science, numerical simulation becomes a effective tool for city design. The urban environment numerical simulation is based on a simulation method coupled with three-dimensional Computational Fluid Dynamics analysis, three-dimensional radiation analysis, and one-dimensional heat conduction analysis (Huang et al, 2005). Fig. 5 shows the flowchart for this numerical simulation. First, boundary conditions are set up from various input conditions including meteorological data, geometries of urban area, etc. Second, a three-dimensional radiation calculation is performed. Then, the temperature distribution inside the ground or wall is calculated by solving an unsteady one-dimensional heat conduction equation. Three-dimensional coupled convection and water vapor transportation calculations are performed continuously by adding new boundary conditions for the surface temperature distribution of the ground and wall and air-conditioning heat load obtained from the radiation and conduction calculation. The coupled simulation of convection, radiation and conduction is then completed by repeating these operations in series. This numerical simulation adapts for an unstructured computational grid suitable for a complex urban area. The detail of calculations for radiation and surface temperature can be found in the paper of Huang et al (2005). This method can give a detailed three dimensional distributions of many environmental parameters, such as, wind velocity, temperature, humidity, pollutants. Therefore, using the method, the environment characteristics of the target area including comfort level, energy consumption and sustainability can be evaluated.

  

   Fig.6 shows two examples of urban environment design in local scale using above numerical simulation. The left figure (Oguro et al, 2001) shows wind environment simulation around buildings. It indicates that ‘wind road’, which mean that the river wind can be lead smoothly through the built-up urban area leading to a comfort environment, can be formed through optimization of building arrangement. The right figure (Chen et al, 2004) shows the thermal environment in an apartment area. It indicates that the thermal environment is improved through reasonable arrangement of trees and piloti. As shown in the examples, a sustainable environment design can be done using the simulation tool.

  5. Conclusions

  Great efforts have been done on the emergency response and recovery process after Great Wenchuan earthquake. Triangle theory of public safety provides an good understanding of emergency management. As parts of emergency management, emergency response and recovery are not separate, recovery process should be an integral part of the emergency response. The sustainable city design in the recovery process should be an extension of emergency response. Two approaches including from large and local scale view after disaster are reviewed and the effectiveness are shown.

  References

  W. Fan, Y. Liu. Analysis of urban public safety system structure, Urban Management Science & Technology, 11, 5, 38-41, 2009.

  M. Ishikawa. The restoration plan of Dujiangyan after the Great Sichuan earthquake disaster in 2008, 7th International Symposium on New Technologies for Urban Safety of Mega Cities in Asia, Beijing, China, October, 2008.

  H. Huang, R. Ooka, S. Kato. Urban thermal environment measurements and numerical simulation for an actual complex urban area covering a large district heating and cooling system in summer, Atmospheric Environment, 39, 34, 6362-6375, 2005.

  M. Oguro, S. Murakami, et al. Control of river wind by building arrangement using CFD simulation, Research report of Kanto Branch meeting of Architectural Institute of Japan, 4054, 2001.

  H. Chen, R. Ooka, K. Harayama, S. Kato, X. Li. Study on outdoor thermal environment of apartment block in Shenzhen, China with coupled simulation of convection, radiation and conduction, Energy and Buildings, 36, 1247-1258, 2004.  

  应急响应的延伸-灾后的可持续性城市设计

  黄弘

  清华大学公共安全研究中心, 北京 100084

  摘要

  本文首先分析了基于公共安全三角形理论的应急管理理念。理论认为公共安全包含突发事件、承灾载体、应急管理三方面,贯穿这三者的是灾害要素—可能导致灾害事故的物质、能量和信息。之后指出作为应急管理的一部分,应急响应和恢复重建不是各自独立的行为,恢复重建应成为应急响应的一部分。考虑可持续性的新城市设计是恢复重建的重要组成部分,可以认为是应急响应的延伸。本文介绍了从区域尺度和街区尺度对城市进行设计的方法,设计应该从应急响应行为开始时就应该进行。

 
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