The inclusion of intraurban inequalities in urban growth models

The last IPCC report highlighted that the urban expansion to areas exposed to climate-driven natural hazards might significantly increase disaster risk in the near future. Understanding risk as the combination of hazard, exposure and vulnerability, these increased trends will be more expressive among the economically and socially marginalized urban residents, particularly in informal settlements. A major cause of this process is spatial intraurban inequalities. The urban poor are not only more vulnerable to natural hazards, e.g., due to a lack of resources; they are also often driven towards the less valuable areas, including hazardous locations such as flood plains and steeper hillslopes, which likely increase their exposure. However, disaster risk research still lacks more holistic tools to simulate and better understand the interrelations among urban expansion, intraurban inequalities, and exposure to natural hazards. We aim to develop an urban growth model that incorporates different socioeconomic groups to investigate the impact of these inequalities on their hazard exposure. We developed our model following the multilevel modeling framework for urban growth. First, a demand module quantifies the amount of urban growth that is expected for each socioeconomic group. Then, a spatial allocation module determines where this growth will take place to fulfill these demands. In the allocation, the most probable locations of future urban areas are individually determined for each group as a function of driving forces. These include biophysical and socioeconomic factors such as terrain slope, elevation, and distance to infrastructure. We applied the model in the municipality of Rio de Janeiro, Brazil, while accounting for three different income groups. Preliminary results indicate that the characteristics of new urban areas change significantly as a function of the income class, with a strong pattern of spatial segregation. Low-income households were found to have a higher probability of being located on steeper terrain than middle- and high-income households. In addition, new low-income urban areas were also found to be more distant from the city center, the coastline, and the main city infrastructure including subway and train stations. These results demonstrate the relevance of incorporating existing inequalities into urban growth models, especially in developing spatial planning policies in accordance with existing risks to natural hazards.