Evaluation of Resilience of Urban Decay Texture against Earthquake using GIS (Case study: District 2 of Bandar Abbās Municipality)

The city of Bandar Abbas is facing a high risk of earthquakes, which makes it necessary to identify and rehabilitate the decay texture. Improper land use location, inefficient communication network, compact texture, high densities, improper distribution of urban open spaces, etc., are crucial in increasing earthquake damages. This study evaluated the resilience of decayed texture against earthquakes using multi-criteria decision-making methods in district 2 of Bandar Abbas. The decayed texture included the neighborhoods of Nāyland, Khājeh Attā, Chahestāni, and Kamarbandi. In the AHP method, the highest housing resilience was for North Nāyband with 68.6%, Southern Nāyband with 45.8%, and Khājeh Ata with 41% of accommodation was in the next category. At the same time, Chahestāni and Kamarbandi, with 4.6% and 5.7% of the housing, respectively, had proper resilience. Vulnerability analysis also showed that 28.2% of belt buildings and 10.7% of Chahestāni had a high vulnerability. In the ANP method, the slope and distance from the fault with the weight of 0.003 and 0.007, respectively, had the lowest values. The material type and the number of building floors with a weight of 0.119 and 0.072 were the most important indicators. In the GIS environment, the layers overlapped, and the results showed that 69.2% of Nāyband North and 40.9% of Khājeh Atta had high resilience. 32.8% of Kamarbandi using were highly vulnerable, and 43.1% were relatively vulnerable with the first ranking, and the Chahestāni was in the second-ranking. A comparison of the results of the two decision-making methods showed the better performance of the ANP method. Extended Abstract Introduction Natural hazards, with their various types and extent of influence, are recurring and destructive phenomena that have always existed during the earth's life and have always been a danger to humans since the creation of humankind. Therefore, it can be acknowledged that no society claims to be safe from natural hazards, and humans always face harmful mental and objective effects. By reviewing the literature on historical events in the country, it can be seen that Iran, due to its location-spatial structures, has always suffered from many natural crises and has been among the most vulnerable parts of the world to natural hazards. The fact is that natural disasters pose a growing threat to the well-being and development of rural communities, and the damage caused by natural disasters affects the rural community both in terms of recurrence and the damage they cause.MethodologyThe method was descriptive-analytical. First, effective criteria for evaluating the case area's worn-out urban fabric are identified. Then, using the pairwise comparison method, the existing criteria were compared. In this case, each criterion based on the degree of importance was assigned a number between 1 and 9 (1: equal importance, 2: weak superiority of one variable over another, 9: most important). The collected information was analyzed according to database-based methods and using hierarchical analysis models and network and software analysis based on the GIS approach. The steps are as follows:1- Determining the locating criteria using the results of previous studies and research, collecting information based on the defined criteria2- Creating a database and mapping criteria3- Weight of criteria: In this stage, priorities in the form of weights enter the decision model. The purpose of weighting the criteria is to express the importance of each criterion compared to other criteria. In this research, two weighting methods, AHP and ANP, were used, which were briefly described.4- Presenting the results By combining the information layers with the application of the corresponding weight, the zoning of the worn-out urban fabric is determined.Questionnaire informationThe questionnaires were presented as a pairwise comparison matrix of criteria. Twenty-five experts completed questionnaires by random sampling. The mean value was taken from each cell of the matrix. To analyze the AHP method, the data were entered into Expert Choise software, and Super Decisions software was used to implement the ANP method.Results and discussionEvaluation of resilience of dilapidated neighborhoods in Bandar Abbas district 2 using the AHP methodDifferent criteria in location and zoning are not aligned, decision making should be made in a multidimensional space. In such situations, multi-criteria evaluation methods can be used, considering that in these methods it is assumed that each criterion is a separate axis or dimension. The hierarchical structure includes objectives, criteria, or possible criteria and options used in prioritization. Hierarchy is because decision-making elements (decision-making options and criteria) can be summarized at different levels.  Therefore, the criteria are placed in a matrix, and binary comparisons are made between them. In fact, a matrix is formed, and its values are compared in pairs according to the importance of each criterion to each other. After forming the comparison matrix, the relative weights of the criteria are obtained as follows, respectively.Step 1: Calculate the sum of the values of each column in the pairwise comparison matrix.Step 2: The standardization of matrix numbers is so that each component of the matrix derived from pair comparison is divided into the sum of its column, and the normalized pair comparison matrix is obtained.Step 3: Calculate the components' average in each row of the standardized matrix. That is, dividing the total standardized points for each row by the number of criteria resulting from each column matrix. These averages are estimates of the relative weight of the compared criteria. Finally, the final weight is obtained. The final weight is the basis for decision-making and is used as the efficiency ratio of each criterion in achieving the final goal. As can be seen, the total importance coefficient of the criteria is equal to 1, indicating the relativity of the importance of the criteria. One of the advantages of the analytical hierarchy process is the possibility of evaluating compatibility in judgments to determine the importance coefficient of criteria. If this coefficient is smaller or equal to 0.1, the compatibility in judgments is accepted. Otherwise, it should be revised in judgments. In other words, the binary comparison matrix of criteria must be re-formed.ConclusionIn the analytical hierarchy system, the weight of building materials and population density criteria with a score of 0.334 and 0.23, respectively, as the most important indicators and criteria of public open spaces with a weight of 0.023 have the least importance in vulnerability to earthquake crisis. The experience of recent earthquakes has shown that the type of materials used in the structure is more important than other effective parameters in earthquake vulnerability. In such a way, whatever long-lasting materials have been used in the structure, the severity of vulnerability to earthquake decreases, and the resilience of buildings increases. The highest housing resilience belongs to the North Nayband neighborhood with 68.6% of buildings on high resilience floors, the Southern Nayband neighborhoods with 45.8% and Khajeh Atta with 41% of housing in the next categories of resilience against earthquakes. While, Chahestani and Beltway neighborhoods have good resilience in 4.6% and 5.7% of the neighborhoods, respectively. Also, the vulnerability analysis results show that 28.2% of the buildings in the Beltway neighborhood and 10.7% of the uses of the Chahestani neighborhood have high vulnerability.FundingThere is no funding support.Authors’ Contribution Authors contributed equally to the conceptualization and writing of the article. All of the authors approved the content of the manuscript and agreed on all aspects of the workConflict of InterestAuthors declared no conflict of interest.Acknowledgments We are grateful to all the persons for scientific consulting in this paper.