Determining site suitability of evacuation shelters using GIS

Determining site suitability of evacuation shelters using GIS

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Introduction
Every year, countries around the globe, including Korea, are undergoing enormous human and property damages resulting from natural disasters such as earthquakes, droughts, floods and artificial disasters like fires, explosions and building collapses. When a fire or disaster occurs, what should be taken into consideration most seriously is evacuation of people and in this regard emergency evacuation shelters become an important thing. Moreover, knowing precise locations of designated emergency evacuation shelters is one of the most crucial measures for evacuation when an emergency occurs. However, the most fundamental problem in relation to the occurrence of a disaster or calamity, is that evacuees are lacking in their understanding of preventing and coping with such disaster or of recovering damages. In order to resolve such problems, efficient and swift management and heightening of citizens” awareness of disasters and calamities is required.

Furthermore, whether emergency evacuation shelters are facilities established in accordance with appropriate standards are ambiguous in many aspects and although there have been some studies of their appropriateness, those aimed at providing precise standards are still being made. At present, the need for criteria to evaluate their appropriateness in order to judge whether emergency evacuation shelters are facilities established in accordance with appropriate standards and whether they need complementation has also emerged. To this end, this study first reviewed previous research on standard elements for emergency evacuation shelters and presented elements enabling quantitative assessment. Second, this study established GIS database with variables produced from the standard elements designed using previous research results. Third, in order to consider the importance of elements to plan emergency evacuation shelters, this study applied AHP, thereby presenting standard elements to evaluate and estimating their relevant importance and priorities. Lastly, this study made a new suggestion through the analysis result by applying the standard elements to the area examined.

Emergency evacuation shelters” stages and process
The Article 2.2 of the Disaster Management Act of Korea defines disaster management as all activities to remove the risk of disaster occurrence and cope with and recover damages from disasters; it interpreted disaster management in a broad sense. In general, the process of disaster management is classified into 4 stages and many researchers including Lee Jae-eun (2000) and Gong Ha-seong (2006) came up with meanings of each of the four stages and calculated their relative importance and priorities. Accordingly, this study also classified disaster stages regarding emergency evacuation shelters into mitigation of, preparedness for, response to and recovery from disasters.

First, mitigation of disasters consists of determination of plans to reduce risks and long-term activities to decrease the degree of risks to human lives and properties. This stage refers to a stage for removal, control, or prevention of factors that may trigger disasters. Second, the stage of preparedness for disasters is a stage for development of capabilities to prepare activities of coping with disasters in advance and includes the following activities. As disaster and calamity management activities, there are pre-training, securing and storage of resources and maintenance of collaborative system. Third, response to disasters are activities in which disaster management organisations perform their duties and functions when disasters occur and this stage refers to reducing the possibilities of another losses and minimising problems that may occur during the stage of recovery in connection with activities in the risk mitigation and preparedness stages (Lee Jae-eun, 2000). Lastly, the final stage of recovery from disasters is a long-term activity process from right after a crisis has occurred until the damaged area is restored to the original state before the crisis and at the same time refers to ongoing activities that provide support from the early recovery period until the area returns to normal conditions. This stage may be divided into short-term temporary emergency recovery of the afflicted”s mental and physical damages and long-term and permanent restoration to the original state (Kim Hyeong-yeol, 1987).

Methodology in detail

Derivation of standard elements and calculation of weights
Through the previous research reviewed earlier, this study derived quantifiable standard elements, with the upper hierarchical structure in the evaluation model aimed at developing assessment elements to evaluate the appropriateness of emergency evacuation shelters consisting of mitigation of, preparedness for, response to and recovery of disasters when they occur. The lower hierarchical structure is made up of: management of zones with high risk of disasters, current status of the establishment of factories that manufacture hazardous facilities and management of disaster occurrence history; floor area ratio referring to floor occupancy area per capita, the number of accommodated persons per area, water supply amount available to a person per day and the degree of response to and knowledge of disasters by each type; structure exploration, emergency medical activities, securing and management of accommodations and accessibility meaning traffic control and order maintenance; and the cause of disaster occurrence and investigation of problems.

Like the above, this study structured development of assessment elements to evaluate the appropriateness of emergency evacuation shelters into two hierarchies and conducted a survey on a population of doctors and professors performing disaster-related tasks by sending them an e-mail or visiting them in order to measure relative importance and priorities of the areas and elements to evaluate the appropriateness of emergency evacuation shelters in its empirical analysis stage. The pair comparison method, in which two elements were compared with each other in each question, was used in the questionnaire, and in each stage the quantifiable elements in each hierarchy were presented with 4 elements in the upper hierarchy and 11 elements in the lower hierarchy. Regarding the scale of importance, the derivation of weights was most effective when it was based on the research result by Satty and therefore AHP was utilised in accordance with experts” opinions.


Table 1. Standard Elements and Calculation of Weights

Decision making based on analytic hierarchy process
When a decision should made to determine an optimal measure among multiple natural disaster management strategies, comparative evaluation of such measures should be made but in case evaluation standards include both qualitative and quantitative elements, simple and reasonable decision making is very hard. Therefore, a method to determine relative importance of evaluation standards in order to select an optimal measure is needed and to this end AHP is considered useful (Lee Jong-yeol, 2007).

In early 1970s, Thomas Satty, professor of Pennsylvania University, developed AHP as part of measures to improve inefficiency of decision making in the process of collaborating with world-class economists and game theory experts in the Arms Control and Disarmament Agency of the US State Department; AHP derives major factors and sub-factors from a complex problem by setting its hierarchy and their importance through pair wise comparison. The whole process of AHP decision making is analysed and resolved by each stage, thereby enhancing objectivity of decision making, and the consistency of weights derived by pair wise comparison is verified, thereby heightening the robustness of decision making. This technique is a qualitative evaluation method in which quantitative measurement or assessment is difficult and therefore is suitable for effectiveness evaluation which requires qualitative judgment (O” Neill, 1998).

AHP enables analysis and decomposition of a problem with an approach similar to human reasoning system and that a result may be obtained in a quantitative form by systematically making relative importance or preference into ratio scales. This technique uses methods adopted through empirical analysis and thorough mathematical verification process in scale selection, weight calculation procedure and sensitivity analysis and therefore, is theoretically highly valued.

Application and empirical analysis

Selection of research area
Yongsan-gu of Seoul was selected as the area of this study. It has been a center of inland water transport of the central region using the Han River waterway and an area of active trade. Yongsan-gu has a total of 20 dongs and it is a central area in terms of economy and transportation and culture and a large number of middle-income households live. Six bridges among bridges across the Han River and the Gyeongbuseon cross the area of Yongsan; it is a gateway that connects downtowns of Seoul and it is a transportation hub of Seoul. Yongsan used to be associated with the military force; it became a massive military base after Japan”s invasion and a transportation hub after the railway was constructed. Despite its geographically central location in Seoul, it had an image of an underdeveloped area. However, it is now a city in spotlight again thanks to international business complexes including Seoul”s landmarks of skyscrapers around the railway depot, formation of a 270 m2 huge ecological park in accordance with US military base transfer and a plan of Yongsan Link, an integral three-dimensional space that connects all the zones underground.

Moreover, development of 1 million pyeong (about 3.3 million m2) around the Han River into a district for international information and administrative business has been initiated in earnest and it is expected to be transformed into an economic, cultural and administrative hub of Seoul in the future. For these reasons this study selected Yongsan as its research area.

Construction and application of data
Materials used to construct data for this study included the cadastral map and building register of Yongsan-gu and statistical yearbooks of Seoul. In order to calculate the sum of total floor areas of buildings by usage, the cadastral map was employed as spatial data and the building register as attribute data. The locations and usages of designated emergency evacuation shelters in Yongsan-gu in the section of the Republic of Korea Civil Defense Corps (ROKCDC) on the homepage of the National Disaster Information Center and average population density of Yongsan-gu from statistical yearbooks of Seoul were utilised. Furthermore, data were constructed by referring to the operational manual guideline for ROKCDC facilities and equipment. Finally, accessibility of roads was calculated using an ArcGIS tool and data on buildings by usage was extracted.

The analysis result was that regarding the relative importance of the four stages in evaluated areas of emergency evacuation shelters, mitigation of disasters ranked first, followed by recovery from disasters, response to disasters and preparedness for disasters. In the stage of mitigation of disasters, the weight of management of zones with high risk of disasters was about 9 per cent and that of management of disaster occurrence history was low at just 4 per cent. To represent the significance of buildings by providing scores to them, the War Commemoration Service Association and the National Museum of Korea obtained 1.971 and 1.877, respectively.

In the stage of preparedness for disasters, floor occupancy area per capita which means floor area ratio was given the highest weight. Moreover, evacuees had more knowledge about how to respond to each type of disaster than expected. To derive values of the War Commemoration Service Association and the National Museum of Korea by applying weights, the former and the latter obtained 0.411 and 0.352, respectively, with a wide difference of about 0.10. In the stage of response to disasters, traffic control and order maintenance meaning accessibility was placed highest importance on at 0.280 and 0.020, respectively. In the stage of recovery from disasters, the two areas did not differ much regarding the causes of disasters and relevant problems. The analysis result of the studied area was that the War Commemoration Service Association ranked fist and the National Museum of Korea ranked last as an emergency evacuation shelter. The National Museum of Korea, although it was a public structure, was lacking in medical facilities and had low accessibility, resulting in getting the lowest score.


Table 2. Evaluation Result by Element of Emergency Evacuation Shelters of the Studied Area

 



Figure 1. Status of the research area evacuating and the application of AHP

Conclusion
This study intended to present plan elements for emergency evacuation shelters by comparing and evaluating relative importance and priorities in standard elements for spatial planning of emergency evacuation facilities in order to present their relative importance and priorities. First, this study explained the concept of disasters and calamities and presented elements enabling quantitative evaluation of standard elements of emergency evacuation shelters by reviewing relevant prior research. Second, variables were produced based on standard elements designed through previous research and then GIS database was constructed. Third, AHP, in which a questionnaire on experts was utilised in order to consider relative importance of plan elements for emergency evacuation shelters, was applied, thereby presenting standard elements for evaluation and calculating their relative importance and priorities. Lastly, the standard elements presented by this study were applied to the studied area and the analysis result was derived. The importance among the four stages of evaluation areas was in the order of mitigation of, recovery from, response to and preparedness for disasters. The analysis result of the studied area was that the War Commemoration Service Association ranked first and the National Museum of Korea ranked last as an emergency evacuation shelter. The National Museum of Korea, although it was a public structure, was lacking in medical facilities and had low accessibility in terms of its location, resulting in getting the lowest score.

In conclusion, evaluating the effectiveness of disaster and calamity management policies using evaluation elements established through GIS and multiple-criteria spatial decision making is very meaningful in that it can guarantee citizens” safety right, prevent life and property loss and maintain trusting relationship between citizens and the government. This study is expected to make it easier to judge whether a facility meets the appropriateness standards reflecting situations of diverse disasters, calamities and wars and response systems or whether it needs complementation with spatial decision making.

Further, it is regarded that considering location elements and accessibility of each facility in order to secure safe emergency evacuation shelters is desirable. Objective and precise location analysis and decision making in relation to emergency evacuation facilities will need establishment of standardized evaluation standards and diverse research on methodologies that can evaluate such standards.

As limitations of this study, it is not based on generalised theoretical discussion in establishing policy goals and standard systems as well as evaluation areas and items and therefore it is subjective, because it focused on review of previous studies. Therefore, follow-up research needs to include more number of expert groups in order to further refine and generalize its evaluation model.

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