1. Introduction
Urban marginalization, as one of the consequences of uneven development, brings profound physical, social, and environmental challenges. Zanjan, the capital of Zanjan Province, located in the northwest region of Iran, has experienced rapid population growth and accelerated physical expansion in recent decades. This expansion has predominantly occurred in a dispersed, peripheral pattern, spreading into the surrounding lands. The peripheral areas of Zanjan, which were once primarily villages and agricultural lands, have now become arenas for rapid land-use changes, extensive migration, and the formation of heterogeneous urban fabrics. These areas serve as the connecting ring and transitional zone between the city and the countryside and, due to often fragmented and weak governance, are highly vulnerable.
On the other hand, Zanjan Province, and specifically the periphery of Zanjan city, has increasingly faced prolonged droughts, declining precipitation, falling groundwater levels, and reduced surface water flow in recent years. This has undermined the economic and livelihood foundations of the area's inhabitants.
In this context, the core issue of this research is to examine the deep and complex link between two crises: the environmental crisis (water scarcity and drought) and the urban crisis (unbalanced development and informal settlement). This link is forged through the key pathway of population displacement and migration. Drought and water scarcity, by destroying the agricultural and livestock-based livelihoods in the villages and small towns around Zanjan, create a powerful driving force for the forced or voluntary migration of these populations to the fringes of Zanjan city. This migratory flow is often unplanned and unguided.
Consequently, several challenges underscore the critical importance of investigating this issue:
Unbalanced Urban Development: Concentrated and rapid migration to the urban fringe, in the absence of spatial planning and necessary infrastructure provision, leads to dispersed, discontinuous, and heterogeneous horizontal expansion of the city. This reduces urban efficiency, increases service delivery costs, and exacerbates spatial inequalities in access to amenities (such as drinking water, electricity, sewage networks, public transport, green spaces, and educational and healthcare services) between the central and peripheral areas of the city.
Formation and Reinforcement of Informal Settlements: Migrant populations lacking the economic means to reside in planned parts of the city inevitably resort to occupying and constructing dwellings on lands with unclear ownership, agricultural lands, riverbanks, or unstable slopes—areas typically located in these peripheral zones. This phenomenon fuels informal settlement. Due to the lack of permits and planning, these settlements lack minimum safety, health, and environmental standards and become hotspots for various social, economic, and physical problems.
A Vicious Cycle of Vulnerability: The residents of these new informal settlements are themselves often exposed to new risks stemming from inappropriate location (such as floods, landslides, and pollution) and suffer from limited access to resources and services. This reinforces a vicious cycle of poverty, marginalization, and vulnerability. Furthermore, the destruction of surrounding agricultural lands for housing further weakens local food production capacity and the region's resilience.
Based on this, the main research question of this study is: "What are the factors influencing the physical transformations of migration in the periphery of Zanjan city, with an emphasis on drought, and which ones hold greater importance?" Answering this question will provide a deeper understanding of the environmental-physical dynamics of Zanjan city and offer a scientific basis for integrated policymaking in water resource management, regional development, and urban planning.
 
2. Methodology
This study is applied in purpose and objectivist-interpretivist in epistemological perspective, adopting a mixed-methods approach with a concurrent strategy. For data analysis, a one-sample t-test and hybrid multi-criteria decision-making models (FARAS + FCOPRAS) were used in the quantitative part, and Grounded Theory was employed in the qualitative part.
 
3. Results
The results showed that data analysis indicates the physical developments on the outskirts of Zanjan follow a dual and dangerous pattern of rapid but low-quality expansion. On one hand, there is a high pace of land-use change and settlement growth (averages above 3.5), and on the other hand, low housing quality, inadequate access to water and sewage (averages below 3), and high vulnerability to natural hazards (average 4.3) indicate the formation of fragile settlements that seriously threaten the health and safety of residents.
Then, based on the Grounded Theory method, the destruction of rural livelihood resilience and the intensification of environmental hazards were identified as causal factors; structural deficiencies in resource governance and the lack of livelihood alternatives as contextual factors; and the physical-economic attractions of the city outskirts along with weak urban supervision and planning as intervening factors in the physical developments. Among these, the root factors at the origin (destruction of rural livelihoods and intensifying drought), with the highest score, are the main drivers of migration and subsequent physical developments. In contrast, the pull factors at the destination (such as cheap land and weak urban oversight) have played a secondary and facilitating role, highlighting the forced, rather than voluntary, nature of this migration.
 
5. Conclusion
The findings of this study revealed that physical developments on the outskirts of Zanjan have led to the formation of an unstable and vulnerable pattern. However, tracing the roots of this phenomenon based on Grounded Theory challenges the common perception in urban planning. Contrary to the prevailing belief that typically attributes the growth of marginalization to false urban attractions, this study emphasizes that the core of this issue stems from push factors at the origin (the collapse of rural livelihoods and increasing droughts). Urban pull factors (such as cheap land) have merely acted as a catalyst or facilitator in the process of forced migration.
 
Author Contributions
In the preparation and writing of this article, all authors (first and second) have contributed equally and jointly. All stages of the research, from study design and data collection to analysis of results and final writing of the article, are the result of collaboration and collective agreement of all authors.
 
Data Availability Statement
Data available on request from the authors.
 
Acknowledgements
We are very grateful to everyone who assisted us in conducting this research.
 
Ethical Considerations
All authors affirm that this research was conducted in accordance with ethical standards, with no data fabrication, falsification, or plagiarism.
 
Funding
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
 
Conflict of Interest
The authors declare no conflict of interest