ارزیابی اثرات مخاطرات طبیعی بر ساختار کالبدی شهرها، مطالعه موردی: شهر جدید لار (مقاله علمی وزارت علوم)
درجه علمی: نشریه علمی (وزارت علوم)
آرشیو
چکیده
طبق گزارش سازمان ملل متحد، ایران در سال 2003 از نظر تعداد زلزله و کشته شدگان در رتبه اول جهان قرار دارد. دلیل اصلی این امر آسیب پذیری بالای اکثر شهرهای ایران نزدیک به 80 درصد است. شهر لار در سال 1339 زلزله 6.1 ریشتر را شاهد بود که سبب ویرانی شهر گردید. امروزه این شهر به عنوان بزرگ ترین مرکز سکونتی لارستان با دو بخش پویا شهر قدیم در شمال غرب دشت لار و شهر جدید بعد از ویرانی ناشی از زلزله بر روی مخروط افکنه تنگ اسد در جنوب دشت قرار دارد. هدف پژوهش بررسی میزان آسیب پذیری کالبدی شهر قدیم و جدید در برابر زلزله با مجموعه شاخص های کلان و خرد و مقایسه تحلیلی این دو بخش از شهر است. جامعه آماری پژوهش کل محدوده با تمامی محلات شهر جدید و قدیم لار است. جمع آوری اطلاعات به صورت کتاب خانه ای میدانی بوده و داده های اصلی از اطلاعات سرشماری مرکز آمار و همچنین شهرداری لار صورت گرفته است. بررسی و تجزیه وتحلیل داده ها نیز با وزن دهی شاخص ها به کمک تکنیک دلفی و سنجش میزان اهمیت آن ها با نظر کارشناسان صورت گرفته در ادامه به کمک مدل های سلسله مراتبی وزن دهی شده و درنهایت با داده های خود در نرم افزار GIS نقشه های آسیب پذیری شاخص ها و نقشه نهایی آسیب پذیری به دست آمده است. نتایج تحقیق حاکی از ن است که میزان آسیب پذیری در بین محلات بسیار متفاوت بوده و عوامل دخیل در این محلات و در محدوده کل شهر به یک اندازه تأثیرگذار نبوده اند، که دلایل گوناگونی در آن ها نقش داشتند ازجمله عوامل کالبدی فیزیکی ساختمان و عوامل فیزیکی محیطی ازجمله خدمات اساسی و زیر بنایی شهر من جمله فضاهای درمانی و بهداشتی. بررسی شاخص های آسیب پذیری حاکی از آن است که نیازمند راهکاری قوی و کارآمد مدیریتی و سازمانی و بعدازآن کالبدی و محیطی جهت کاهش آسیب پذیری و افزایش تاب آوری شهر هستیمEvaluation of the effects of natural hazards on the physical structure of cities: the case study of New city of Lar
Lar city witnessed a 6.1 Richter earthquake in 1960, which destroyed the city. Today, this city is the largest residential center of Larestan, with two dynamic parts of the old city in the northwest of the Lar plain and the new city after the destruction caused by the earthquake, located on the Tangeh Asad alluvial cone in the south of the plain. The research aims to investigate the physical vulnerability of old and new cities against earthquakes with macro and micro indicators and an analytical comparison of these two parts of the city. The statistical population of the research is the entire area, including all the neighborhoods of the old and new city of Lar. Data collection was done in the form of a field library, and the main data was collected from the Statistics Center and Lar Municipality census data. The analysis of the data was also carried out by weighting the indicators with the help of the Delphi technique and measuring importance with the opinion of experts, then weighting was done with the help of hierarchical models, and finally, with the data in the GIS software, maps of the vulnerability of the indicators and the final map of vulnerability were obtained. The results show that the level of vulnerability is very different among the localities, and the factors involved in these localities and the entire city are not equally effective, various reasons played a role in them, including the physical factors of the building and environmental physical factors, including services. The basic infrastructure of the city, including medical and health spaces. Examining the vulnerability indicators indicates that we need a strong and efficient management and organizational solution, as well as physical and environmental solutions, to reduce the vulnerability and increase the resilience of the city.
Introduction
Earthquake is one of the strongest natural hazards that has always caused significant human and economic losses to urban areas. According to its geographical and geological location, Iran is among the ten most earthquake-prone countries in the world. This multiplies the issue of attention to vulnerability in the country. The physical and environmental vulnerability of cities and residential areas against natural hazards is considered very important, and due to adaptation to the rapidly changing world, having an environment that can respond to these hazards and have the necessary resilience is meaningful and essential. Urban form and body consist of macro and microelements. The macro-level elements are related to the overall structure and size of the city, the type of development, the population distribution pattern, and the degree of clustering, and the micro-level elements are related to the design and arrangement of elements such as buildings, open spaces, blocks, neighborhoods, and streets. Together, both form the city's physical-environmental complex, and both are vulnerable to natural hazards. Therefore, for the resilience of the whole city, attention should be paid to the details of each macro and microelement.
Methodology
The current research is a type of user research that seeks to solve the problem of reducing the effects of natural hazards, especially earthquakes in Lar city. In terms of the nature of descriptive research, it is an analysis whose purpose is to know the obvious and hidden angles of the damage caused to the city of Lar due to the earthquake. In order to evaluate the main goal of the research, a large number of indicators were extracted using the content analysis of previous studies, and 4 macro indicators and 11 sub-indices were selected for the study through a survey of professors. By selecting the final indicators of their data from the statistics center, the detailed and comprehensive plan and the municipality of the area were collected and prepared in the form of GIS software to analyze the vulnerability of the city. In order to analyze the obtained data, we started by weighting the indicators and determining their impact on the vulnerability caused by the earthquake. For this purpose, the hierarchical analysis model was used. Finally, all the obtained layers were combined using the Raster Calculator technique, and Lar city's final physical vulnerability map was extracted. The Natural Breaks technique has also been used to classify the final physical vulnerability map and the maps related to each criterion.
Results and discussion
Lar, located in Fars province, is located after the 4th earthquake of May 1960 on the 6.1 Richter scale, which is still considered one of Iran's most powerful earthquakes. Although 6 decades have passed since the earthquake and the formation of a new city, an evaluation is needed to determine the level of physical vulnerability against the earthquake. According to the general division of Lar city, the old city is located in the north of Lar plain with 8 neighborhoods with an area of approximately 8 square kilometers and the new city with an area of about 12 square kilometers and 18 neighborhoods in the south. The research results indicate that out of 8 neighborhoods in the old city, 1 neighborhood with 40%is exposed to very high damage and 4 neighborhoods with 27% are exposed to moderate damage. In the new city, 7 neighborhoods with about 48% are exposed to moderate damage, 7 neighborhoods with 25% are exposed to low damage, and 1 neighborhood with 12% is exposed to high damage, which is unacceptable for the new city with a little history. Also, 40% of the old and new city of Lar is exposed to very high damage, 37% is exposed to moderate damage, and 2% is exposed to very low damage. Considering the history of earthquakes in the area, this is very worrying for the city and requires careful and efficient management before the crisis.
Conclusion
Regarding the physical vulnerability of the city against earthquakes, there are still various influential topics which are different in different cities. Lar also consists of two parts, new and old, so each has its physical characteristics. According to the studies of this research, in the old city, the effective factors in the very high degree of vulnerability, in the order of the first rank in building strength factors, include the following elements as the type of skeleton and materials, the age of the building with 78% of the entire area of the old city texture; the second rank of density factors including the elements as population density, residential density, the granularity of units with 58% of the entire area of the old city texture; the third rank of accessibility factors including the elements as local roads and main roads with 40% of the entire area of the old city texture; and finally, the fourth rank of basic service factors including elements as therapeutic spaces, green and open spaces, temporary accommodation and educational spaces with 39% of the entire area of the old city texture medium vulnerability were the sum of factors and elements that contributed to the vulnerability of the old city. These factors had different effects in the new city, which are the first rank of basic service factors including elements as therapeutic spaces, green and open spaces, temporary accommodation and educational spaces with 48% of the total area of the new city; the second rank of density factors including elements as population density, residential density, unit granularity with 31% of the total area of the new city texture; the third rank of building strength factors including elements as type of skeleton and materials, the age of the building with 29% of the entire area of the new city texture; and the fourth rank of accessibility factors including elements as local roads and main roads with 23% of the total area of the new city have been effective in the vulnerable level of the city. In order to reduce the vulnerability of the city, one should look for solutions before the crisis, which can be rooted in managerial and physical solutions.
Funding
There is no funding support.
Authors’ Contribution
Authors contributed equally to the conceptualization and writing of the article. All of the authors approved thecontent of the manuscript and agreed on all aspects of the work declaration of competing interest none.
Conflict of Interest
Authors declared no conflict of interest.
Acknowledgments
We are grateful to all the scientific consultants of this paper.
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