Inter-scale disaster resilience index: Examples of Eastern Marmara, Kocaeli, and its districts

Abstract

Modern cities have developed differently, influenced by their unique histories and the natural features of their surrounding environments. The extent to which these cities, home to both people and nature, are exposed to various human-induced and natural risks varies based on their developmental paths. These risks can pose serious threats not only to urban populations and ecosystems but also to the cities' functioning. Typically, these risks, which arise from both natural and anthropogenic causes, are categorized as disasters or similar large-scale hazards. When a city faces a disaster, it must effectively respond to the resulting negative outcomes, including loss of life, destruction, injuries, and damage. A city must be capable of withstanding the impacts of the disaster, absorbing the negative consequences internally, and adapting to the altered conditions in the aftermath. Only then can it mitigate the harm caused by such events. In academic literature, this capacity is referred to as "resilience". A city with high disaster resilience is less affected by the negative consequences of such events. Cities that are more frequently exposed to disasters require greater resilience, while those unable to adapt to the effects of disasters are considered vulnerable. To improve urban disaster resilience and reduce vulnerability, decision-makers must first assess and understand the existing level of resilience. Various resilience assessment methodologies have been developed in the literature to understand the current level of urban resilience. This study also focuses on developing and applying such a resilience measurement method. Studies that evaluate multiple indicators collectively to generate findings are referred to as index studies. In the literature, resilience indices based on comparative frameworks typically measure resilience within a specific context by comparing one administrative unit to its neighboring units. The scale of an administrative unit determines the jurisdiction of decision-makers and guides the selection of parameters to be considered for resilience assessment. There are inherent differences in the scope and level of detail between decisions made at higher scales, such as the regional level, and those made at lower scales, such as the district level. Therefore, it is natural that different interventions are implemented at different scales. However, the interrelationship between these scales should not be overlooked in this process. For example, if a parameter is identified as a vulnerability at a higher scale, which of the lower-level administrative units that constitute that scale contribute to this vulnerability? Similarly, if a parameter is identified as a strength at a lower scale, does it also signify resilience for the upper-scale unit it belongs to? Such questions can only be answered by conducting resilience assessments across interrelated administrative units and scales. Index studies focusing on a single scale can produce certain findings within their comparative framework. However, they often fall short in accounting for these findings' underlying drivers and wider implications. The primary aim of this study is to examine how vulnerabilities and resilience at different spatial scales influence one another, and to explore the correlations between these nested units. In line with the study's objective, administrative units at three nested spatial scales were selected as the study area. For the highest scale—the regional scale—the TR4 East Marmara Region, consisting of eight provinces according to the Nomenclature of Territorial Units for Statistics (NUTS) in Türkiye, was chosen. At the intermediate scale, Kocaeli Province, one of the provinces within the East Marmara Region and composed of twelve districts, was selected. Finally, at the lowest scale, the twelve districts of Kocaeli were examined. The comparative framework was established within each scale: between regions in Türkiye, provinces within East Marmara, and districts within Kocaeli. As resilience inherently encompasses multiple dimensions, six thematic resilience indices were developed for the selected study areas: physical, infrastructural, economic, institutional, social, and environmental. Within these themes, relevant indicators were selected to assess exposure and vulnerability to disasters. Since the study area is located within Türkiye, disaster types that are not commonly observed in the country were excluded to enhance relevance, while more emphasis was placed on hazards frequently occurring in the selected regions. A total of 62 indicators were identified across the six contexts, and 128 individual calculations were carried out at different spatial scales. Due to the varying data types, two commonly used normalization methods—z-value and min-max—were applied to standardize the indicators for comparative purposes. These normalization techniques, frequently used in index-based comparative studies in the literature, also served as an additional research output, allowing the study to evaluate which method yielded more meaningful results. Beyond its primary aim, the study also contributes to the identification of priority intervention areas based on local vulnerabilities, an understanding of resilience and vulnerability status across different dimensions, and the selection of the most appropriate normalization method for the context of this analysis. As a result of the study, the integrated evaluation of nested spatial scales revealed a set of findings that would not have emerged in a single-scale analysis. This inter-scale structure enabled the observation of both the similarities and differences between the scales and allowed the identification of the highest resilience levels and the most significant vulnerabilities for each unit. These findings, which would have differed if each study area were evaluated in isolation, were made possible specifically through the inter-scale nature of the analysis, highlighting the importance of scale interaction in resilience assessments. In conclusion, assessing the resilience of a single unit requires more than merely analyzing its own status and that of its neighboring units, as such a limited approach may lead to missing insights and a narrowed scope. Therefore, an inter-scale resilience assessment approach contributes to more objective decision-making processes and facilitates the identification of priority intervention areas.