Bridging Divides for Sustainable Urban Development: How Public-Space Design Fosters Social Cohesion in a Multiethnic Informal Settlement—The Case of Hesar, Hamedan (Iran)

Social cohesion is a core dimension of social sustainability and a prerequisite for inclusive, resilient cities. Rapid rural-to-urban migration often exceeds the capacity of cities to accommodate newcomers, leading many immigrants to settle in informal neighborhoods. These areas, typically composed of diverse ethnic groups with distinct cultural, linguistic, and social backgrounds, frequently face challenges in building social cohesion. This study examines how physical elements of public spaces influence social cohesion in multiethnic informal settlements, using the Hesar Imam Khomeini neighborhood in Hamadan, Iran, as a case study. Hesar, with its rural origins and recent influx of Lor, Kurdish, Turkish, and Fars migrants, provides a unique setting to explore the relationship between the built environment and interethnic relations. A conceptual model was developed based on existing literature, and data were collected through a questionnaire survey using a Likert scale. Partial least squares structural equation modeling (PLS-SEM) was applied to test the hypothesized relationships. The findings demonstrate that physical factors shape social cohesion through a three-stage mechanism: they first foster social interactions among residents, which then contribute to the development of social capital, and ultimately lead to greater social cohesion and integration. These results highlight how inclusive public-space design can support community-based informal-settlement upgrading and sustainable urban development, by strengthening social sustainability outcomes such as cohesion, integration, and resilience.